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Saccharina latissima and Psammechinus miliaris on variable salinity grazed infralittoral rock

Distribution MapBIO Map Legend

Summary

UK and Ireland classification

Description

Sheltered bedrock, boulders and cobbles, in areas of reduced salinity, with kelp Saccharina latissima, and depauperate coralline-encrusted rock supporting few foliose seaweeds but many grazing urchins Psammechinus miliaris and Echinus esculentus. The coralline crusts are typically Lithothamnion glaciale, while the brown crusts can be Pseudolithoderma extensum. Encrusting polychaetes Spirobranchus (formerly Pomatoceros) triqueter, resistant to grazing, are also present on most of the rock. The grazing fauna are a significant component of this biotope; large numbers of Psammechinus miliaris are typically present, although where absent the brittlestar Ophiothrix fragilis may occur. Other grazers prevalent on the rock include the chiton Tonicella marmorea, the limpet Tectura testudinalis and the gastropod Steromphala cineraria. A combination of grazing pressure and lowered salinity maintains a low diversity of species in this biotope, with foliose and filamentous seaweeds generally absent or reduced to small tufts by grazing. In stark contrast to the range of seaweeds present in the Saccharina latissima forests (Slat.Ft) the only red seaweed consistently found in this biotope is Phycodrys rubens. The range of fauna is similarly low, with a conspicuous absence of hydroids and bryozoans. Bedrock and boulders provide a firm substrate on which ascidians Ciona intestinalis and Ascidia mentula and the bivalve Modiolus modiolus can attach. The crabs Pagurus bernhardus and Carcinus maenas can usually be found here, though Necora puber typically is absent due to the brackish conditions. The starfish Asterias rubens along with the whelk Buccinum undatum can be present. The substratum on which this biotope occurs varies from bedrock to boulders or cobbles on sediment. The kelp band is relatively narrow and shallow (upper 5 m) compared to Slat.Ft, although the grazed coralline encrusted rock extends deeper. This depth limit becomes shallower towards the heads of the sealochs.

This biotope is restricted to the west coast of Scotland, usually near the head of fjordic sealochs, which are influenced by freshwater run-off. Where circalittoral rock occurs below this biotope, it often supports a brachiopod/anthozoan community (NovPro); where mixed substrata occur below or adjacent, beds of Modiolus modiolus are common (ModHAs or ModHo).  If the grazing pressure is reduced (i.e. a decrease in the number of grazing echinoderms present) there may be an increase in filamentous and foliose seaweeds although the diversity will remain low compared to full saline sites. (Information from JNCC, 2015, 2022).

Depth range

0-5 m, 5-10 m

Additional information

-

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are within the “Kelp in Variable or Reduced Salinity” habitat complex (IR.LIR.KVS), which are predominantly shallow low energy biotopes found in areas of low or reduced salinity typically in Scotland but also in other sheltered locations around the British Isles e.g. harbours. IR.LIR.KVS.Cod is characterized by dense stands of Codium spp., silt tolerant red seaweeds and sparse Saccharina latissima (syn. Laminaria saccharina). IR.LIR.KVS.SlatPsaVS is characterized by Saccharina latissima but intense Psammechinus miliaris grazing combined with low salinity maintains low biodiversity, resulting in an understorey community of depauperate coralline-encrusted rock with predominantly grazing resistant or mobile fauna e.g. Spirobranchus spp. IR.LIR.KVS.SlatPhyVS is characterized by Saccharina latissima with dense stands of silted filamentous green seaweeds and red seaweeds; Phyllophora crispaPhyllophora pseudoceranoides and Phycodrys rubens.

In undertaking this assessment of sensitivity, an account is taken of knowledge of the biology of all characterizing species in the biotope. For this sensitivity assessment Saccharina latissima (the dominant characterizing algae), and Psammechinus miliaris (the dominant urchin grazers) are the primary foci of research. It is recognized that the understorey red seaweed communities of IR.LIR.KVS.SlatPhyVS also define these biotopes. Examples of important species groups are mentioned where appropriate.

The biotopes IR.LIR.KVS biotope complex is distinguished by the relative abundance of Saccharina latissima, and Codium sp, the diversity of red and brown algae that ranges between low salinity or scour tolerant species, and the presence or absence of grazers.  The sensitivity of the dominant kelp and red algae are probably consistent for most of the pressures assessed. Therefore, except where indicated, all assessments are considered to apply to all the biotopes within the biotope complex.

Resilience and recovery rates of habitat

There are four species of Codium spp. and two sub-species in the UK; Codium fragile subsp. atlanticum, Codium fragile subsp. tomentosoides, Codium bursa, Codium tomentosum and Codium vermilaria (Silva, 1955; Bunker et al., 2012). IR.LIR.KVS.Cod does not specifically refer to 1 (sub) species as characteristic, therefore, the evidence used within this assessment has been sourced from literature cover all 6 species and subspecies. Codium spp. has a perennial life strategy (Bulleri & Airoldi, 2005). Viable zoospores can be produced in the first year of growth from June to autumn (Churchill & Moeller, 1972), spores then germinate and germlings persist through winter undergoing rapid thalli growth when water temperature increases the following spring/summer (Haniask, 1979; Bulleri & Airoldi, 2005). In successive years, the thalli can fragment during winter reducing individuals to a holdfast which may then persist throughout the winter (Fralick & Methieson, 1972), in early spring (April-May) a new frond will develop from the holdfast (Trowbridge, 1995, 1996). Codium fragile gametes can settle and germinate on a variety of substrata including rock fractions, as well as shellfish, coralline algae, serpulid casts and solitary ascidians (Bulleri & Airoldi, 2005). Recruitment is, however, strongly influenced by temperature (see below), salinity (see below), wave exposure and the availability of bare space at the time of gamete release (Trowbridge, 1995, 1998, 1999; Bégin & Scheibling, 2003). Fralick & Methieson (1972) suggested cold temperatures caused Codium spp. thalli to fragment and that fragmented sections of Codium were then capable of reattachment to hard substrata by means of colourless filaments which grow from the point of fragmentation. In most cases, it took several weeks for re-attachment to occur but in summer fragments could re-attach within 3-6 days.

Saccharina latissima is a perennial kelp characteristic of wave sheltered sites of the North East Atlantic, distributed from northern Portugal to Spitzbergen, Svalbard (Birkett et al., 1998b; Connor et al., 2004; Bekby & Moy, 2011; Moy & Christie, 2012). Saccharina latissima is capable of reaching maturity within 15-20 months (Sjøtun, 1993) and has a life expectancy of 2-4 years (Parke, 1948). Maximum growth has been recorded in late winter early spring, in late summer and autumn growth rates slow (Parke, 1948; Lüning, 1979; Birkett et al., 1998b). The overall length of the sporophyte may not change during the growth season due to the marginal (distal) erosion of the blade, but extension growth of the blade has been measured at 1.1 cm/day, with total length addition of over 2.25m of tissue per year (Birkett et al., 1998b). Saccharina latissima has a heteromorphic life strategy. Large numbers of zoospores are released from sori located centrally on the blade between autumn and winter. Zoospores settle onto rock and develop into gametophytes, and after fertilization germinate into juvenile sporophytes. Kelp zoospores are expected to have a large dispersal range; however, zoospore density and the rate of successful fertilization decreases exponentially with distance from the parental source (Fredriksen et al., 1995). Hence, recruitment following disturbance can be influenced by the proximity of mature kelp beds producing viable zoospores to the disturbed area (Kain, 1979; Fredriksen et al., 1995).

A large pressure for Laminaria hyperborea biotopes (e.g. IR.HIR.KFaR.LhypR) is urchin grazing, particularly from the species Echinus esculentusParacentrotus lividus and Strongylocentrotus droebachiensis. Multiple authors (Steneck et al., 2002; Steneck et al., 2004; Rinde & Sjøtun, 2005; Norderhaug & Christie, 2009; Smale et al., 2013) have reported dense aggregations of sea urchins to be a principal threat to Laminaria hyperborea biotopes of the North Atlantic. Intense urchin grazing creates expansive areas known as “urchin barrens”, in which a shift can occur from Laminaria hyperborea dominated biotopes to those characterized by coralline encrusting algae, with a resultant reduction in biodiversity (Leinaas & Christie, 1996; Steneck et al., 2002, Norderhaug & Christie, 2009). Continued intensive urchin grazing pressure on Laminaria hyperborea biotopes can inhibit Laminaria hyperborea recruitment (Sjøtun et al., 2006) and cause urchin barrens to persist for decades (Christie et al., 1998; Steneck et al., 2004; Rinde & Sjøtun, 2005). A kelp recolonization experiment conducted by Leinaas & Christie (1996) removed Strongylocentrotus droebachiensis from “urchin barrens” and observed a succession effect. It was observed that the substratum was initially colonized by filamentous macroalgae and within 2 weeks Saccharina latissima colonized and persisted for two years. However, after 2-4 years Laminaria hyperborea dominated the community. Despite Laminaria hyperborea’s eventual dominance within the community Leinaas & Christie (1996) demonstrated that Saccharina latissima can colonize cleared areas rapidly.

In 2002 a 50.7-83 % decline of Saccharina latissima was discovered in the Skaggerak region, South Norway (Moy et al., 2006; Moy & Christie, 2012). Survey results indicated a sustained shift from Saccharina latissima communities to those of transient filamentous algal communities. The reason for the community shift was unknown, but low water movement in wave and tidally sheltered areas combined with the impacts of dense human populations e.g. increased land run-off, was suggested to be responsible for the dominance of transient turf macro-algae. Multiple stressors such as eutrophication, increasing regional temperature, increased siltation and overfishing may also be acting synergistically to cause the observed habitat shift.

Psammechinus miliaris is a sea urchin distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927). In the British Isles, it can occur in dense aggregation within sheltered locations e.g. Scottish sea lochs, and its distribution frequently coincides with that of Saccharina latissima (Kelly, 2000). Psammechinus miliaris grazes on a wide array of algae and encrusting organisms, including Saccharina latissima (IR.LIR.KVS.SlatPsaVS) (Kelly, 2000; Connor et al., 2004). Psammechinus miliaris can reach sexual maturity within the first year, reproduce each successive year, (Elmhirst, 1922) and are reported to live up to 10 years (Allain, 1978). Gametogenesis begins in May and spawning usually occurs between June and August. Depending on food availability, planktonic larvae will then typically settle out within 20-21 days.  The gut is fully developed 5-7 days after settlement and juveniles begin grazing (Kelly, 2001).

The red algae Phyllophora crispa & Phyllophora pseudoceranoides which combined with filamentous green seaweeds characterize the understorey community of IR.LIR.KVS.SlatPhyVS. Depending on the level of impact, recovery of the turf may occur through repair and regrowth of damaged fronds, regrowth from crustose bases or via recolonization of rock surfaces where all the plant material is removed. Although there are few case studies following recovery, some general trends are apparent. All the red algae (Rhodophyta) exhibit distinct morphological stages over the reproductive life history. This phenomenon is known as heterotrichy or heteromorphy and describes cases where the algal thallus consists of two parts, a prostrate creeping system exhibiting apical growth and functioning as a holdfast. The thalli can regrow from these crusts where they remain supporting the recovery of the biotope (Mathieson & Burns, 1975; Dudgeon & Johnson, 1992). The basal crusts are perennial, tough, resistant stages that prevent other species from occupying the rock surface and allow rapid regeneration and where these remain, they provide a significant recovery mechanism.

Phyllophora sp. are distributed across the North Atlantic and recorded from the Bay of Bisacy (Molenaar & Breeman, 1994up to Trondhiem, Norway in Europe (Norwegian Seaweeds, 2015). Phyllophora sp. are perennial plants but blades are lost and regrown each year (Newroth, 1972; Molenaar & Breeman, 1994). Culture experiments demonstrated that the time for Phyllophora pseudoceranoides to reach sexual maturity was highly temperature dependent. When kept at 10 or 5°C Phyllophora pseudoceranoides specimens from Helgoland, Germany and Roscoff, France began sporulation within three months. However, there was considerable variation, and specimens kept at ≥15°C took ≤30 months to begin sporulation (Molenaar & Breeman, 1994). These observations were made under controlled experimental conditions. Therefore, natural environmental variability is likely to lengthen or possibly shorten the time taken for Phyllophora sp. to begin sporulation however it is likely that in a natural setting Phyllophora pseudoceranoides would reach maturity within 2 years (High resilience). Please note, although some general trends are apparent, recovery rates, for example, will be greatly influenced by whether the crust stages remain from which the thalli can regrow. If a high proportion of bases are lost, then recovery will depend on either vegetative regrowth from remaining bases and/or the supply of propagules from neighbouring populations. Dispersal is limited and propagule supply will be influenced by site-specific factors, particularly local water transport, recovery would likely take 2-10 years (Medium resilience).

Resilience assessment. Saccharina latissima has potentially rapid recovery rates, recovering from Strongylocentrotus droebachiensis ‘urchin Barrens’ appearing after a few weeks (Leinaas & Christie, 1996), and can reach maturity within 15-20 months (Birkett et al., 1998b). Codium spp. can produce viable spores within their first year of growth, and annually fragmented sections of thalli can re-attach to hard substrata. Psammechinus miliaris can become sexually mature in its first year. Red seaweeds can potentially recover within a single growing season. Resilience is assessed as ‘High’ where resistance is ‘High’. Where resistance is assessed as ‘Medium’ (loss of <25 % of individuals or cover), and the bases remain then recovery is assessed as ‘High’. Where resistance is assessed as ‘Low’ or ‘None’, and a high proportion of red seaweed bases are lost then recovery will depend on either vegetative re-growth of red seaweeds from remaining bases or propagule supply from neighbouring populations, resilience would be assessed as ’Medium’.

Climate Change Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Low Very Low High
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

The distribution of kelp is strongly influenced by climatic conditions; therefore, kelp species are extremely sensitive to the ongoing ocean warming (Kain, 1979; Van Den Hoek, 1982; Breeman, 1990; Lüning, 1990; Assis et al., 2016; Smale, 2020). Northern distribution boundaries are set by winter temperatures that are lethal, or summer temperatures too low for growth and/or reproduction, whilst southern limits are set by high lethal summer temperatures or winter temperatures too high for induction of a crucial step in the life cycle (Breeman, 1990). Kelps have a high dependence on ocean temperatures, which make them highly vulnerable to ocean warming (Assis et al., 2014). As temperatures increase, populations found towards the upper limit of their temperature range may be adversely affected by warming as physiological thresholds are exceeded (Wiens, 2016). Thermal stress can lead to mortality and consequent population-level effects, such as decreased abundance, altered size structure, local extinction and range contractions (Smale, 2020). 

Saccharina latissima is a polar to temperate macroalgae distributed from Greenland to the coast of Portugal and, in the NW Atlantic, is found as far south as New York State, USA. At its southern distribution in New York, temperatures can regularly reach ≥20°C for six weeks or more during summer months (Gerard & Du Bois, 1988).

Saccharina latissima has an optimal growth temperature between 10 and 15°C, with growth reducing by 50-70% at 20°C, and all experimental specimens disintegrating after seven days at 23°C (Bolton & Lüning, 1982). The temperature isotherm of 19-20°C has been reported as limiting Saccharina latissima growth (Müller et al., 2009). Temperature is an environmental factor controlling the development of the microscopic stages of Saccharina latissima, with crucial changes in survival, growth, and gametogenesis occurring within a few degrees of its upper thermal limits (Redmond, 2013). The optimal germination temperature for Saccharina latissima is between 2°C and 12°C, with gametophyte survival between 23-25°C (Müller et al., 2009). Germination rates drop at 22°C, with surviving gametophytes smaller than those grown at lower temperatures (Redmond, 2013). Park et al. (2017) observed reductions in the percentage of sporophytes produced at 15°C when compared to values produced at 5°C and 10°C. 

In the field, Saccharina latissima has shown significant regional variation in its acclimation response to changing environmental conditions.  For example, Gerard & Dubois (1988) observed that sporophytes of Saccharina latissima that were regularly exposed to ≥20°C tolerated these high temperatures, whereas sporophytes from other populations that rarely experience ≥17°C showed 100% mortality after 3 weeks of exposure to 20°C.

Saccharina latissima has suffered a dramatic decline in the Skagerrak region, Norway, where community structure has shifted from Saccharina latissima forests to communities dominated by filamentous macroalgae (Moy & Christie, 2012). In 2006, Andersen et al. (2011) transplanted Saccharina latissima into areas from where this species had been lost previously to determine whether the kelp could grow and mature. High mortality occurred from August-November each year. In 2008, only six of the seventeen original transplanted Saccharina latissima sporophytes survived (approx. 65% mortality rate). All surviving sporophytes were heavily fouled by epiphytic organisms (estimated cover of 80 & 100%). Between 1960 and 2009, sea surface temperatures in the region had regularly exceeded 20°C and so had the duration at which temperatures remain above 20°C. High sea temperatures have been linked to the slow growth of Saccharina latissima, which is likely due to a decrease in the photosynthetic ability of Saccharina latissima, and an increase in vulnerability to epiphytic loading, bacterial and viral attacks (Anderson et al., 2011).

Assis et al. (2018) predicted that, under the highest emission scenario (RCP 8.5), the range of Saccharina latissima would move northwards, retreating from their southern-most locations, with a predicted loss of Saccharina latissima from the southwest coast of the UK.  

Psammechinus miliaris is a sea urchin distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927; www.obis.org). In the British Isles, Psammechinus miliaris can occur in dense aggregations within sheltered locations e.g. Scottish sea lochs, and its distribution frequently coincides with that of Saccharina latissima (Kelly, 2000). Psammechinus miliaris grazes on a wide array of algae and encrusting organisms, including live Saccharina latissima (as in IR.LIR.KVS.SlatPsaVS) (Kelly, 2000; Connor et al., 2004).

Psammechinus miliaris generally occurs in water temperatures of 4–17°C. Temperature, photoperiod and food availability are considered to be factors that control the reproduction of echinoids (Kelly, 2001). Kelly (2000) suggested that cold water over winter is important for the completion of gametogenesis in female Psammechinus miliaris, as significantly fewer females in the temperature-controlled treatment (with seawater maintained at 9°C) produced mature eggs.

Many of the red algae species associated with the understorey turf can tolerate warm water temperatures. Corallina officinalis may tolerate between -4 to 28°C (Lüning, 1990), although when Colthart & Johansen (1973) exposed this species to a number of different temperatures, they found that growth was maintained at 18°C and ceased at 25°C. Abrupt temperature changes (10°C in California, Seapy & Littler 1984; 4.8 to 8.5°C, Hawkins & Hartnoll, 1985) resulted in dramatic declines. However, in both cases recovery was rapid, suggesting that the crustose bases survived. 

Spirobranchus triqueter occurs as far south as the Mediterranean. Therefore, it will be subject to a wider range of temperatures than experienced in the British Isles (www.obis.org). Castric-Fey (1983) found that animals settling during spring showed the best growth rate and the best larval settlement occurred in the summer months. Therefore, it is assumed that Spirobranchus triqueter has some tolerance to increased temperatures. 

Sensitivity Assessment. UK populations of Saccharina latissima are found in the middle of the species distribution and are known to be able to survive at higher temperatures than currently experienced around the UK. The ability to tolerate summer seawater temperatures of >20°C in populations at their southern geographic limit is thought to be a genetic adaptation (Gerard & Du Bois, 1988), and maybe crucial in the persistence of this species around the UK, as seawater temperatures rise. 

This biotope IR.LIR.KVS.SlatPsaVS is only found in Scotland, where sea surface temperatures range between 6 and 16°C (www.seatemperature.org). Therefore, under the middle and high emission scenarios, sea temperatures are predicted to rise by between 3-4°C by the end of this century, leading to Scottish winter seawater temperatures of 9-10°C and summer highs of 19-20°C. Populations of Saccharina latissima and Psammechinus miliaris may be able to adapt to cope with a gradual rise in ocean temperatures of this magnitude. Therefore, resistance is assessed as ‘Medium’, but resilience is assessed as ‘Very Low’, as the loss is likely to be a long-term decline, due to the long-term nature of ocean warming. Hence, sensitivity is assessed as ‘Medium’ sensitivity to ocean warming in the middle and high emission scenario benchmark levels.

Under the extreme scenario, where sea temperatures rise by 5°C with potential summer temperatures reaching 21°C and winter low temperatures of 11°C in Scotland (www.seatemperature.org), both Saccharina latissima and Psammechinus miliaris are likely to experience some negative impacts. Psammechinus miliaris may be negatively impacted, as an increase in winter seawater temperatures potentially reduces the window for reproduction. Although Saccharina latissima can survive a temperature of 20°C, growth and reproduction can be reduced, although genetic adaption in the long term may improve survivability. Therefore, resistance is assessed as ‘Low’, and resilience is assessed as ‘Very low’ so that sensitivity is assessed as ‘High’ to ocean warming under the extreme scenario

Medium Very Low Medium
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

The distribution of kelp is strongly influenced by climatic conditions; therefore, kelp species are extremely sensitive to the ongoing ocean warming (Kain, 1979; Van Den Hoek, 1982; Breeman, 1990; Lüning, 1990; Assis et al., 2016; Smale, 2020). Northern distribution boundaries are set by winter temperatures that are lethal, or summer temperatures too low for growth and/or reproduction, whilst southern limits are set by high lethal summer temperatures or winter temperatures too high for induction of a crucial step in the life cycle (Breeman, 1990). Kelps have a high dependence on ocean temperatures, which make them highly vulnerable to ocean warming (Assis et al., 2014). As temperatures increase, populations found towards the upper limit of their temperature range may be adversely affected by warming as physiological thresholds are exceeded (Wiens, 2016). Thermal stress can lead to mortality and consequent population-level effects, such as decreased abundance, altered size structure, local extinction and range contractions (Smale, 2020). 

Saccharina latissima is a polar to temperate macroalgae distributed from Greenland to the coast of Portugal and, in the NW Atlantic, is found as far south as New York State, USA. At its southern distribution in New York, temperatures can regularly reach ≥20°C for six weeks or more during summer months (Gerard & Du Bois, 1988).

Saccharina latissima has an optimal growth temperature between 10 and 15°C, with growth reducing by 50-70% at 20°C, and all experimental specimens disintegrating after seven days at 23°C (Bolton & Lüning, 1982). The temperature isotherm of 19-20°C has been reported as limiting Saccharina latissima growth (Müller et al., 2009). Temperature is an environmental factor controlling the development of the microscopic stages of Saccharina latissima, with crucial changes in survival, growth, and gametogenesis occurring within a few degrees of its upper thermal limits (Redmond, 2013). The optimal germination temperature for Saccharina latissima is between 2°C and 12°C, with gametophyte survival between 23-25°C (Müller et al., 2009). Germination rates drop at 22°C, with surviving gametophytes smaller than those grown at lower temperatures (Redmond, 2013). Park et al. (2017) observed reductions in the percentage of sporophytes produced at 15°C when compared to values produced at 5°C and 10°C. 

In the field, Saccharina latissima has shown significant regional variation in its acclimation response to changing environmental conditions.  For example, Gerard & Dubois (1988) observed that sporophytes of Saccharina latissima that were regularly exposed to ≥20°C tolerated these high temperatures, whereas sporophytes from other populations that rarely experience ≥17°C showed 100% mortality after 3 weeks of exposure to 20°C.

Saccharina latissima has suffered a dramatic decline in the Skagerrak region, Norway, where community structure has shifted from Saccharina latissima forests to communities dominated by filamentous macroalgae (Moy & Christie, 2012). In 2006, Andersen et al. (2011) transplanted Saccharina latissima into areas from where this species had been lost previously to determine whether the kelp could grow and mature. High mortality occurred from August-November each year. In 2008, only six of the seventeen original transplanted Saccharina latissima sporophytes survived (approx. 65% mortality rate). All surviving sporophytes were heavily fouled by epiphytic organisms (estimated cover of 80 & 100%). Between 1960 and 2009, sea surface temperatures in the region had regularly exceeded 20°C and so had the duration at which temperatures remain above 20°C. High sea temperatures have been linked to the slow growth of Saccharina latissima, which is likely due to a decrease in the photosynthetic ability of Saccharina latissima, and an increase in vulnerability to epiphytic loading, bacterial and viral attacks (Anderson et al., 2011).

Assis et al. (2018) predicted that, under the highest emission scenario (RCP 8.5), the range of Saccharina latissima would move northwards, retreating from their southern-most locations, with a predicted loss of Saccharina latissima from the southwest coast of the UK.  

Psammechinus miliaris is a sea urchin distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927; www.obis.org). In the British Isles, Psammechinus miliaris can occur in dense aggregations within sheltered locations e.g. Scottish sea lochs, and its distribution frequently coincides with that of Saccharina latissima (Kelly, 2000). Psammechinus miliaris grazes on a wide array of algae and encrusting organisms, including live Saccharina latissima (as in IR.LIR.KVS.SlatPsaVS) (Kelly, 2000; Connor et al., 2004).

Psammechinus miliaris generally occurs in water temperatures of 4–17°C. Temperature, photoperiod and food availability are considered to be factors that control the reproduction of echinoids (Kelly, 2001). Kelly (2000) suggested that cold water over winter is important for the completion of gametogenesis in female Psammechinus miliaris, as significantly fewer females in the temperature-controlled treatment (with seawater maintained at 9°C) produced mature eggs.

Many of the red algae species associated with the understorey turf can tolerate warm water temperatures. Corallina officinalis may tolerate between -4 to 28°C (Lüning, 1990), although when Colthart & Johansen (1973) exposed this species to a number of different temperatures, they found that growth was maintained at 18°C and ceased at 25°C. Abrupt temperature changes (10°C in California, Seapy & Littler 1984; 4.8 to 8.5°C, Hawkins & Hartnoll, 1985) resulted in dramatic declines. However, in both cases recovery was rapid, suggesting that the crustose bases survived. 

Spirobranchus triqueter occurs as far south as the Mediterranean. Therefore, it will be subject to a wider range of temperatures than experienced in the British Isles (www.obis.org). Castric-Fey (1983) found that animals settling during spring showed the best growth rate and the best larval settlement occurred in the summer months. Therefore, it is assumed that Spirobranchus triqueter has some tolerance to increased temperatures. 

Sensitivity Assessment. UK populations of Saccharina latissima are found in the middle of the species distribution and are known to be able to survive at higher temperatures than currently experienced around the UK. The ability to tolerate summer seawater temperatures of >20°C in populations at their southern geographic limit is thought to be a genetic adaptation (Gerard & Du Bois, 1988), and maybe crucial in the persistence of this species around the UK, as seawater temperatures rise. 

This biotope IR.LIR.KVS.SlatPsaVS is only found in Scotland, where sea surface temperatures range between 6 and 16°C (www.seatemperature.org). Therefore, under the middle and high emission scenarios, sea temperatures are predicted to rise by between 3-4°C by the end of this century, leading to Scottish winter seawater temperatures of 9-10°C and summer highs of 19-20°C. Populations of Saccharina latissima and Psammechinus miliaris may be able to adapt to cope with a gradual rise in ocean temperatures of this magnitude. Therefore, resistance is assessed as ‘Medium’, but resilience is assessed as ‘Very Low’, as the loss is likely to be a long-term decline, due to the long-term nature of ocean warming. Hence, sensitivity is assessed as ‘Medium’ sensitivity to ocean warming in the middle and high emission scenario benchmark levels.

Under the extreme scenario, where sea temperatures rise by 5°C with potential summer temperatures reaching 21°C and winter low temperatures of 11°C in Scotland (www.seatemperature.org), both Saccharina latissima and Psammechinus miliaris are likely to experience some negative impacts. Psammechinus miliaris may be negatively impacted, as an increase in winter seawater temperatures potentially reduces the window for reproduction. Although Saccharina latissima can survive a temperature of 20°C, growth and reproduction can be reduced, although genetic adaption in the long term may improve survivability. Therefore, resistance is assessed as ‘Low’, and resilience is assessed as ‘Very low’ so that sensitivity is assessed as ‘High’ to ocean warming under the extreme scenario

Medium Very Low Medium
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

The distribution of kelp is strongly influenced by climatic conditions; therefore, kelp species are extremely sensitive to the ongoing ocean warming (Kain, 1979; Van Den Hoek, 1982; Breeman, 1990; Lüning, 1990; Assis et al., 2016; Smale, 2020). Northern distribution boundaries are set by winter temperatures that are lethal, or summer temperatures too low for growth and/or reproduction, whilst southern limits are set by high lethal summer temperatures or winter temperatures too high for induction of a crucial step in the life cycle (Breeman, 1990). Kelps have a high dependence on ocean temperatures, which make them highly vulnerable to ocean warming (Assis et al., 2014). As temperatures increase, populations found towards the upper limit of their temperature range may be adversely affected by warming as physiological thresholds are exceeded (Wiens, 2016). Thermal stress can lead to mortality and consequent population-level effects, such as decreased abundance, altered size structure, local extinction and range contractions (Smale, 2020). 

Saccharina latissima is a polar to temperate macroalgae distributed from Greenland to the coast of Portugal and, in the NW Atlantic, is found as far south as New York State, USA. At its southern distribution in New York, temperatures can regularly reach ≥20°C for six weeks or more during summer months (Gerard & Du Bois, 1988).

Saccharina latissima has an optimal growth temperature between 10 and 15°C, with growth reducing by 50-70% at 20°C, and all experimental specimens disintegrating after seven days at 23°C (Bolton & Lüning, 1982). The temperature isotherm of 19-20°C has been reported as limiting Saccharina latissima growth (Müller et al., 2009). Temperature is an environmental factor controlling the development of the microscopic stages of Saccharina latissima, with crucial changes in survival, growth, and gametogenesis occurring within a few degrees of its upper thermal limits (Redmond, 2013). The optimal germination temperature for Saccharina latissima is between 2°C and 12°C, with gametophyte survival between 23-25°C (Müller et al., 2009). Germination rates drop at 22°C, with surviving gametophytes smaller than those grown at lower temperatures (Redmond, 2013). Park et al. (2017) observed reductions in the percentage of sporophytes produced at 15°C when compared to values produced at 5°C and 10°C. 

In the field, Saccharina latissima has shown significant regional variation in its acclimation response to changing environmental conditions.  For example, Gerard & Dubois (1988) observed that sporophytes of Saccharina latissima that were regularly exposed to ≥20°C tolerated these high temperatures, whereas sporophytes from other populations that rarely experience ≥17°C showed 100% mortality after 3 weeks of exposure to 20°C.

Saccharina latissima has suffered a dramatic decline in the Skagerrak region, Norway, where community structure has shifted from Saccharina latissima forests to communities dominated by filamentous macroalgae (Moy & Christie, 2012). In 2006, Andersen et al. (2011) transplanted Saccharina latissima into areas from where this species had been lost previously to determine whether the kelp could grow and mature. High mortality occurred from August-November each year. In 2008, only six of the seventeen original transplanted Saccharina latissima sporophytes survived (approx. 65% mortality rate). All surviving sporophytes were heavily fouled by epiphytic organisms (estimated cover of 80 & 100%). Between 1960 and 2009, sea surface temperatures in the region had regularly exceeded 20°C and so had the duration at which temperatures remain above 20°C. High sea temperatures have been linked to the slow growth of Saccharina latissima, which is likely due to a decrease in the photosynthetic ability of Saccharina latissima, and an increase in vulnerability to epiphytic loading, bacterial and viral attacks (Anderson et al., 2011).

Assis et al. (2018) predicted that, under the highest emission scenario (RCP 8.5), the range of Saccharina latissima would move northwards, retreating from their southern-most locations, with a predicted loss of Saccharina latissima from the southwest coast of the UK.  

Psammechinus miliaris is a sea urchin distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927; www.obis.org). In the British Isles, Psammechinus miliaris can occur in dense aggregations within sheltered locations e.g. Scottish sea lochs, and its distribution frequently coincides with that of Saccharina latissima (Kelly, 2000). Psammechinus miliaris grazes on a wide array of algae and encrusting organisms, including live Saccharina latissima (as in IR.LIR.KVS.SlatPsaVS) (Kelly, 2000; Connor et al., 2004).

Psammechinus miliaris generally occurs in water temperatures of 4–17°C. Temperature, photoperiod and food availability are considered to be factors that control the reproduction of echinoids (Kelly, 2001). Kelly (2000) suggested that cold water over winter is important for the completion of gametogenesis in female Psammechinus miliaris, as significantly fewer females in the temperature-controlled treatment (with seawater maintained at 9°C) produced mature eggs.

Many of the red algae species associated with the understorey turf can tolerate warm water temperatures. Corallina officinalis may tolerate between -4 to 28°C (Lüning, 1990), although when Colthart & Johansen (1973) exposed this species to a number of different temperatures, they found that growth was maintained at 18°C and ceased at 25°C. Abrupt temperature changes (10°C in California, Seapy & Littler 1984; 4.8 to 8.5°C, Hawkins & Hartnoll, 1985) resulted in dramatic declines. However, in both cases recovery was rapid, suggesting that the crustose bases survived. 

Spirobranchus triqueter occurs as far south as the Mediterranean. Therefore, it will be subject to a wider range of temperatures than experienced in the British Isles (www.obis.org). Castric-Fey (1983) found that animals settling during spring showed the best growth rate and the best larval settlement occurred in the summer months. Therefore, it is assumed that Spirobranchus triqueter has some tolerance to increased temperatures. 

Sensitivity Assessment. UK populations of Saccharina latissima are found in the middle of the species distribution and are known to be able to survive at higher temperatures than currently experienced around the UK. The ability to tolerate summer seawater temperatures of >20°C in populations at their southern geographic limit is thought to be a genetic adaptation (Gerard & Du Bois, 1988), and maybe crucial in the persistence of this species around the UK, as seawater temperatures rise. 

This biotope IR.LIR.KVS.SlatPsaVS is only found in Scotland, where sea surface temperatures range between 6 and 16°C (www.seatemperature.org). Therefore, under the middle and high emission scenarios, sea temperatures are predicted to rise by between 3-4°C by the end of this century, leading to Scottish winter seawater temperatures of 9-10°C and summer highs of 19-20°C. Populations of Saccharina latissima and Psammechinus miliaris may be able to adapt to cope with a gradual rise in ocean temperatures of this magnitude. Therefore, resistance is assessed as ‘Medium’, but resilience is assessed as ‘Very Low’, as the loss is likely to be a long-term decline, due to the long-term nature of ocean warming. Hence, sensitivity is assessed as ‘Medium’ sensitivity to ocean warming in the middle and high emission scenario benchmark levels.

Under the extreme scenario, where sea temperatures rise by 5°C with potential summer temperatures reaching 21°C and winter low temperatures of 11°C in Scotland (www.seatemperature.org), both Saccharina latissima and Psammechinus miliaris are likely to experience some negative impacts. Psammechinus miliaris may be negatively impacted, as an increase in winter seawater temperatures potentially reduces the window for reproduction. Although Saccharina latissima can survive a temperature of 20°C, growth and reproduction can be reduced, although genetic adaption in the long term may improve survivability. Therefore, resistance is assessed as ‘Low’, and resilience is assessed as ‘Very low’ so that sensitivity is assessed as ‘High’ to ocean warming under the extreme scenario

None Very Low High
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Marine heatwaves are extreme weather events defined as periods of extreme sea surface temperature that persists for days to months (Frölicher et al., 2018). Marine heatwaves are predicted to occur more frequently, last for longer and at increased intensity by the end of this century under both middle and high emission scenarios (Frölicher et al., 2018). Marine heatwaves are known to cause significant impacts to kelp forests, particularly if a population is found towards the edge of its southern limit (Smale et al., 2019). 

Saccharina latissima has disappeared almost completely from the Danish estuary Limfjorden, where maximum surface temperatures in summer have increased by 0.7°C per decade over the last 40 years while the number of days with temperatures above 20°C has increased dramatically from 1-2 days year to >25 days year (Pedersen, 2015). Similarly, Saccharina latissima has been lost from the Skagerrak coast of Norway, which is thought to be due to an increase in summer temperatures, coupled with eutrophication (Moy & Christie, 2012).

Under experimental conditions, Nepper-Davidson et al. (2019) exposed a northern (Denmark) population of Saccharina latissima to a simulated three-week heatwave of three different intensities; 18, 21 and 24°C. When exposed to heatwaves of 18 and 21°C there was a decrease in photosynthesis and growth. When a 24°C was simulated, 91% of sporophytes were dead within a week, and the fronds of the few survivors were disintegrating, so the experiment was terminated (Nepper-Davidsen et al., 2019). These results suggest that this species is unlikely to survive heatwaves of the length and magnitude predicted by the end of this century for both the middle and high emission scenarios in the southern UK.

Simonson et al. (2015) investigated the impacts of four temperature treatments (11°C, 14°C, 18°C & 21°C) on Saccharina latissima tissue over three weeksHistological analysis showed temperature mediated tissue damage, including holes, splitting of the medulla, damage to the meristoderm and loss of differentiation between tissue layers at temperatures between 14-21°C. 

Psammechinus miliaris commonly occurs in water temperatures of 4-17°C, with populations of Psammechinus miliaris distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927). Psammechinus miliaris occurs in intertidal rockpools, where temperature can be > 10°C warmer than seawater during summer, with large diurnal and seasonal fluctuations (Daniel & Boyden, 1975), which suggests Psammechinus miliaris has some temperature tolerance. Hence, periods of warming are unlikely to have a great effect on populations of Psammechinus miliaris, however, no evidence of the effects of marine heatwaves on Psammechinus miliaris was found. Psammechinus miliaris, require cold water temperatures over the winter for the completion of gametogenesis in females (Kelly, 2001), therefore marine heatwaves during the winter months could impact reproduction. In addition, marine heatwaves can cause changes to the distribution and activity of grazers (Bennett et al., 2015). 

Sensitivity Assessment. This biotope IR.LIR.KVS.SlatPsaVS is only found in Scotland, therefore under the middle emission scenario, if heatwaves occurred every three years, with a maximum intensity of 2°C for 80 days by the end of this century, this could lead to summer sea temperatures reaching up to 21°C in Scotland. These temperatures may limit Saccharina latissima growth and cause physiological damage, but these temperatures are unlikely to cause mortality. If a heatwave occurred in winter, this could lead to winter temperatures rising to 11°C, which could potentially lead to suppression of sexual reproduction in Psammechinus miliaris during the heatwave, although this is not expected to have large population-level effects (Read & Cumming, 1967). Under the middle emission scenario, resistance is assessed as ‘High’ and resilience is assessed as ‘High’, as no recovery is necessary. Therefore, this biotope SlatPsaVS has been assessed as ‘Not sensitive’ to the middle emission scenario.

Under the high emission scenario, if heatwaves occur every two years by the end of this century, reaching a maximum intensity of 3.5°C for 120 days, this could lead to the heatwave lasting the entire summer with temperatures reaching up to 23°C in the summer in Scotland or 13°C in the winter. Under this scenario, if a heatwave occurs in the summer, it is likely to cause widespread mortality of Saccharina latissima. Therefore, resistance has been assessed as ‘None’. As widespread mortality may lead to a lack of viable sporophytes for recruitment, resilience has been assessed as ‘Very low.’ Therefore, this biotope SlatPsaVS is assessed as having ‘High’ sensitivity to marine heatwaves under the high emission scenario.

High High Not sensitive
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Marine heatwaves are extreme weather events defined as periods of extreme sea surface temperature that persists for days to months (Frölicher et al., 2018). Marine heatwaves are predicted to occur more frequently, last for longer and at increased intensity by the end of this century under both middle and high emission scenarios (Frölicher et al., 2018). Marine heatwaves are known to cause significant impacts to kelp forests, particularly if a population is found towards the edge of its southern limit (Smale et al., 2019). 

Saccharina latissima has disappeared almost completely from the Danish estuary Limfjorden, where maximum surface temperatures in summer have increased by 0.7°C per decade over the last 40 years while the number of days with temperatures above 20°C has increased dramatically from 1-2 days year to >25 days year (Pedersen, 2015). Similarly, Saccharina latissima has been lost from the Skagerrak coast of Norway, which is thought to be due to an increase in summer temperatures, coupled with eutrophication (Moy & Christie, 2012).

Under experimental conditions, Nepper-Davidson et al. (2019) exposed a northern (Denmark) population of Saccharina latissima to a simulated three-week heatwave of three different intensities; 18, 21 and 24°C. When exposed to heatwaves of 18 and 21°C there was a decrease in photosynthesis and growth. When a 24°C was simulated, 91% of sporophytes were dead within a week, and the fronds of the few survivors were disintegrating, so the experiment was terminated (Nepper-Davidsen et al., 2019). These results suggest that this species is unlikely to survive heatwaves of the length and magnitude predicted by the end of this century for both the middle and high emission scenarios in the southern UK.

Simonson et al. (2015) investigated the impacts of four temperature treatments (11°C, 14°C, 18°C & 21°C) on Saccharina latissima tissue over three weeksHistological analysis showed temperature mediated tissue damage, including holes, splitting of the medulla, damage to the meristoderm and loss of differentiation between tissue layers at temperatures between 14-21°C. 

Psammechinus miliaris commonly occurs in water temperatures of 4-17°C, with populations of Psammechinus miliaris distributed across the North East Atlantic from Morocco to northern Scandinavia (Mortensen, 1927). Psammechinus miliaris occurs in intertidal rockpools, where temperature can be > 10°C warmer than seawater during summer, with large diurnal and seasonal fluctuations (Daniel & Boyden, 1975), which suggests Psammechinus miliaris has some temperature tolerance. Hence, periods of warming are unlikely to have a great effect on populations of Psammechinus miliaris, however, no evidence of the effects of marine heatwaves on Psammechinus miliaris was found. Psammechinus miliaris, require cold water temperatures over the winter for the completion of gametogenesis in females (Kelly, 2001), therefore marine heatwaves during the winter months could impact reproduction. In addition, marine heatwaves can cause changes to the distribution and activity of grazers (Bennett et al., 2015). 

Sensitivity Assessment. This biotope IR.LIR.KVS.SlatPsaVS is only found in Scotland, therefore under the middle emission scenario, if heatwaves occurred every three years, with a maximum intensity of 2°C for 80 days by the end of this century, this could lead to summer sea temperatures reaching up to 21°C in Scotland. These temperatures may limit Saccharina latissima growth and cause physiological damage, but these temperatures are unlikely to cause mortality. If a heatwave occurred in winter, this could lead to winter temperatures rising to 11°C, which could potentially lead to suppression of sexual reproduction in Psammechinus miliaris during the heatwave, although this is not expected to have large population-level effects (Read & Cumming, 1967). Under the middle emission scenario, resistance is assessed as ‘High’ and resilience is assessed as ‘High’, as no recovery is necessary. Therefore, this biotope SlatPsaVS has been assessed as ‘Not sensitive’ to the middle emission scenario.

Under the high emission scenario, if heatwaves occur every two years by the end of this century, reaching a maximum intensity of 3.5°C for 120 days, this could lead to the heatwave lasting the entire summer with temperatures reaching up to 23°C in the summer in Scotland or 13°C in the winter. Under this scenario, if a heatwave occurs in the summer, it is likely to cause widespread mortality of Saccharina latissima. Therefore, resistance has been assessed as ‘None’. As widespread mortality may lead to a lack of viable sporophytes for recruitment, resilience has been assessed as ‘Very low.’ Therefore, this biotope SlatPsaVS is assessed as having ‘High’ sensitivity to marine heatwaves under the high emission scenario.

Medium Very Low Medium
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Increasing levels of CO2 in the atmosphere have led to the average pH of sea surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005), with it expected to drop up to a further 0.35 units by the end of this century, dependent on emission scenario. Marine autotrophs will generally benefit from ocean acidification, through an increase in the availability of aqueous COfor photosynthesis (Koch et al., 2013). 

Research on most kelp species has revealed a positive or neutral effect of ocean acidification (Roleda et al., 2012, Fernández et al., 2015, Nunes et al., 2015, Iñiguez et al., 2016b, a), except for one study, that found ocean acidification negatively impacted photosynthesis and growth in the southern hemisphere species, Ecklonia radiata (Britton et al., 2016).

Under experimental COenrichment at levels expected by the end of this century, germination rates of Saccharina latissima were the same as control samples but gametophyte size increased, suggesting a benefit for juvenile stages of this species (Roleda et al., 2012). Nunes et al. (2015) found that experimental exposure of adult Saccharina latissima to enhanced CO2 led to an increase in net primary production, whilst Gordillo et al. (2015) found that enhanced CO2 led to increased photosynthesis and growth. In contrast, Iñiguez et al. (2016) found no increase in carbon fixation under elevated CO2 conditions. Whilst contrasting in findings, these studies suggest that ocean acidification will not negatively impact Saccharina latissima

Dupont et al. (2010) analysed the literature and found that echinoderms are generally robust to ocean acidification, although different life stages and species are affected differently. Miles et al. (2007) suggested that Psammechinus miliaris would be sensitive to a pH drop of 0.5 units, as specimens were unable to regulate internal pH when exposed to a short-term (8 days) experimental decrease in pH, plus there was evidence of dissolution of the skeleton. These impacts were much more pronounced at lower pH (< 7). However, studies that have exposed urchins to longer acclimation periods have found different impacts of ocean acidification. Studies that have presented stressors in a shock-type exposure (as above) may reflect stress response outcomes rather than the results of gradual change in climate (Suckling et al., 2014).

Cross generation echinoderm studies have observed a variety of responses to the progeny produced by adults that have been exposed to low pH. The evidence indicates that the effects on progeny depend on the level of acidification and the conditioning duration of the parents (Byrne et al., 2019). Suckling et al. (2014) found that when Psammechinus miliaris larvae were raised from parents pre-exposed to low pH conditions (pH 7.7 compared to control pH of 7.98), settlements rates were similar to control larvae, and the test (i.e. the urchin shell) diameter was larger, which suggested that this species can acclimate and possibly adapt to low pH conditions. Similarly, Clark et al. (2018b) observed that gene expression profiles associated with transgenerational plasticity contributed to Psammechinus miliaris larval resilience when the adults were conditioned to low pH. Also, Psammechinus miliaris is found in intertidal rockpools, where pH can vary by 3 units throughout the year, with large diurnal and seasonal variation (Morris & Taylor, 1983), which suggests some degree of tolerance to changes in pH.

From observations at natural vent sites, Connell et al. (2018) observed that increased CO2 enrichment reduced the abundance and feeding rates of primary grazers (urchins, Evechinus chloroticus), allowing turf algae to increase in abundance. Therefore, ocean acidification could cause changes to community structure, such as turf algae displacing kelp.

Studies on the impacts of ocean acidification on the calcareous tube structure of serpulidae polychaete worms observed reductions of tube elongation, elasticity and strength when exposed to reduced pH conditions (Chan et al.,2012b; Li et al., 2014; Dıáz-Castanẽda et al., 2019). Dıáz-Castanẽda et al (2019) observed pH to affect trochophore size and post-settlement tube growth, with post-settlement tubes half the size of those at current ocean pH levels. Li et al (2014) observed changes to the structure, volume and density of the tubes, with reductions in hardiness and elasticity, in addition to tube crushing force reduced by 64%. The reduction in tube size and hardiness could impact the survival of the species with increased predation and reduction in the ability to withstand wave force (Chan et al., 2012b; Li et al., 2014). 

Corallina officinalis is a highly calcified, erect, red algae. Results of experimental COenrichment suggest that this species could be significantly negatively affected by future ocean acidification. Hofmann et al. (2012) found that growth and photosynthesis decreased as a result of a 0.3 unit decrease in pH. Further investigation showed that skeletal CaCO3 decreased with increasing COat levels expected for both the middle emission and high emission scenarios, although this decrease was small (< 2%) (Hofmann et al., 2013). Yildiz et al. (2013) showed that although CaCO3 decreased in Corallina officinalis as a result of ocean acidification, photosynthesis increased. When ocean acidification was combined with an increase in UV radiation, which led to an increase in growth rate. They summarised that a decrease in CaCO3 content may not be negative but may lead to this species absorbing and using light differently. Brodie et al. (2014) reported that Corallina species were more resilient to ocean acidification than other calcified algae species, although competition from flesh algal species that benefit from high CO2 may indirectly cause the loss of calcified species from biotopes. Similarly, observations have indicated Corallinales to be adversely affected at locations where CO2 gradients occur naturally, with evidence of Corallinales being outcompeted by heterokont algae at Mediterranean CO2 seeps (Martin & Hall-Spencer, 2017).  

Sensitivity assessment. Kelp forests live in a naturally variable pH habitat, with diel fluctuations of 0.3 - 0.45 pH units (Krause-Jensen et al., 2015, Britton et al., 2016), and boundary layer pH fluctuation of up to 0.8 units (Krause-Jensen et al., 2015). Saccharina latissima is not expected to exhibit negative effects from ocean acidification at levels expected for the end of this century. As Psammechinus miliaris can inhabit intertidal rockpools, where pH can vary by 3 units throughout the year, with large diurnal and seasonal variation, this suggests that Psammechinus miliaris has some degree of tolerance to changes in pH.

Under the middle emission scenario, a pH decrease of 1.5 units is expected to occur by the end of this century. Neither Saccharina latissima nor Psammechinus miliaris are expected to suffer significant negative impacts. Therefore, resistance to ocean acidification under the middle emission scenario has been assessed as ‘High’, whilst resilience is assessed as ‘High’, and this biotope IR.LIR.KVS.SlatPsaVS is assessed as ‘Not sensitive’ to ocean acidification at this benchmark level. 

Under the high emission scenario, 20% of coastal areas are predicted to suffer from seasonal aragonite undersaturation (Ostle et al., 2016). Aragonite undersaturation will primarily occur in Scotland, where this biotope occurs. It is suggested that some negative impacts may be experienced by Psammechinus miliaris under this scenario, and some loss in population size may occur. Therefore, resistance has been assessed as ‘Medium’, whilst resilience is assessed as ‘Very Low’ due to the long term nature of ocean acidification. Under the high emission scenario, sensitivity to ocean acidification is assessed as ‘Medium’.

High High Not sensitive
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Increasing levels of CO2 in the atmosphere have led to the average pH of sea surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005), with it expected to drop up to a further 0.35 units by the end of this century, dependent on emission scenario. Marine autotrophs will generally benefit from ocean acidification, through an increase in the availability of aqueous COfor photosynthesis (Koch et al., 2013). 

Research on most kelp species has revealed a positive or neutral effect of ocean acidification (Roleda et al., 2012, Fernández et al., 2015, Nunes et al., 2015, Iñiguez et al., 2016b, a), except for one study, that found ocean acidification negatively impacted photosynthesis and growth in the southern hemisphere species, Ecklonia radiata (Britton et al., 2016).

Under experimental COenrichment at levels expected by the end of this century, germination rates of Saccharina latissima were the same as control samples but gametophyte size increased, suggesting a benefit for juvenile stages of this species (Roleda et al., 2012). Nunes et al. (2015) found that experimental exposure of adult Saccharina latissima to enhanced CO2 led to an increase in net primary production, whilst Gordillo et al. (2015) found that enhanced CO2 led to increased photosynthesis and growth. In contrast, Iñiguez et al. (2016) found no increase in carbon fixation under elevated CO2 conditions. Whilst contrasting in findings, these studies suggest that ocean acidification will not negatively impact Saccharina latissima

Dupont et al. (2010) analysed the literature and found that echinoderms are generally robust to ocean acidification, although different life stages and species are affected differently. Miles et al. (2007) suggested that Psammechinus miliaris would be sensitive to a pH drop of 0.5 units, as specimens were unable to regulate internal pH when exposed to a short-term (8 days) experimental decrease in pH, plus there was evidence of dissolution of the skeleton. These impacts were much more pronounced at lower pH (< 7). However, studies that have exposed urchins to longer acclimation periods have found different impacts of ocean acidification. Studies that have presented stressors in a shock-type exposure (as above) may reflect stress response outcomes rather than the results of gradual change in climate (Suckling et al., 2014).

Cross generation echinoderm studies have observed a variety of responses to the progeny produced by adults that have been exposed to low pH. The evidence indicates that the effects on progeny depend on the level of acidification and the conditioning duration of the parents (Byrne et al., 2019). Suckling et al. (2014) found that when Psammechinus miliaris larvae were raised from parents pre-exposed to low pH conditions (pH 7.7 compared to control pH of 7.98), settlements rates were similar to control larvae, and the test (i.e. the urchin shell) diameter was larger, which suggested that this species can acclimate and possibly adapt to low pH conditions. Similarly, Clark et al. (2018b) observed that gene expression profiles associated with transgenerational plasticity contributed to Psammechinus miliaris larval resilience when the adults were conditioned to low pH. Also, Psammechinus miliaris is found in intertidal rockpools, where pH can vary by 3 units throughout the year, with large diurnal and seasonal variation (Morris & Taylor, 1983), which suggests some degree of tolerance to changes in pH.

From observations at natural vent sites, Connell et al. (2018) observed that increased CO2 enrichment reduced the abundance and feeding rates of primary grazers (urchins, Evechinus chloroticus), allowing turf algae to increase in abundance. Therefore, ocean acidification could cause changes to community structure, such as turf algae displacing kelp.

Studies on the impacts of ocean acidification on the calcareous tube structure of serpulidae polychaete worms observed reductions of tube elongation, elasticity and strength when exposed to reduced pH conditions (Chan et al.,2012b; Li et al., 2014; Dıáz-Castanẽda et al., 2019). Dıáz-Castanẽda et al (2019) observed pH to affect trochophore size and post-settlement tube growth, with post-settlement tubes half the size of those at current ocean pH levels. Li et al (2014) observed changes to the structure, volume and density of the tubes, with reductions in hardiness and elasticity, in addition to tube crushing force reduced by 64%. The reduction in tube size and hardiness could impact the survival of the species with increased predation and reduction in the ability to withstand wave force (Chan et al., 2012b; Li et al., 2014). 

Corallina officinalis is a highly calcified, erect, red algae. Results of experimental COenrichment suggest that this species could be significantly negatively affected by future ocean acidification. Hofmann et al. (2012) found that growth and photosynthesis decreased as a result of a 0.3 unit decrease in pH. Further investigation showed that skeletal CaCO3 decreased with increasing COat levels expected for both the middle emission and high emission scenarios, although this decrease was small (< 2%) (Hofmann et al., 2013). Yildiz et al. (2013) showed that although CaCO3 decreased in Corallina officinalis as a result of ocean acidification, photosynthesis increased. When ocean acidification was combined with an increase in UV radiation, which led to an increase in growth rate. They summarised that a decrease in CaCO3 content may not be negative but may lead to this species absorbing and using light differently. Brodie et al. (2014) reported that Corallina species were more resilient to ocean acidification than other calcified algae species, although competition from flesh algal species that benefit from high CO2 may indirectly cause the loss of calcified species from biotopes. Similarly, observations have indicated Corallinales to be adversely affected at locations where CO2 gradients occur naturally, with evidence of Corallinales being outcompeted by heterokont algae at Mediterranean CO2 seeps (Martin & Hall-Spencer, 2017).  

Sensitivity assessment. Kelp forests live in a naturally variable pH habitat, with diel fluctuations of 0.3 - 0.45 pH units (Krause-Jensen et al., 2015, Britton et al., 2016), and boundary layer pH fluctuation of up to 0.8 units (Krause-Jensen et al., 2015). Saccharina latissima is not expected to exhibit negative effects from ocean acidification at levels expected for the end of this century. As Psammechinus miliaris can inhabit intertidal rockpools, where pH can vary by 3 units throughout the year, with large diurnal and seasonal variation, this suggests that Psammechinus miliaris has some degree of tolerance to changes in pH.

Under the middle emission scenario, a pH decrease of 1.5 units is expected to occur by the end of this century. Neither Saccharina latissima nor Psammechinus miliaris are expected to suffer significant negative impacts. Therefore, resistance to ocean acidification under the middle emission scenario has been assessed as ‘High’, whilst resilience is assessed as ‘High’, and this biotope IR.LIR.KVS.SlatPsaVS is assessed as ‘Not sensitive’ to ocean acidification at this benchmark level. 

Under the high emission scenario, 20% of coastal areas are predicted to suffer from seasonal aragonite undersaturation (Ostle et al., 2016). Aragonite undersaturation will primarily occur in Scotland, where this biotope occurs. It is suggested that some negative impacts may be experienced by Psammechinus miliaris under this scenario, and some loss in population size may occur. Therefore, resistance has been assessed as ‘Medium’, whilst resilience is assessed as ‘Very Low’ due to the long term nature of ocean acidification. Under the high emission scenario, sensitivity to ocean acidification is assessed as ‘Medium’.

Medium Very Low Medium
Q: Low
A: NR
C: NR
Q: High
A: High
C: High
Q: Low
A: Low
C: Low

Sea-level rise is occurring through a combination of thermal expansion and ice melt.  Sea levels have risen 1-3 mm/yr. in the last century (Cazenave & Nerem, 2004, Church et al., 2004, Church & White, 2006). Sea-level rise is expected to lead to substantial loss of intertidal habitats. Rocky shores backed by cliffs constitute about 80% of oceanic coastlines globally and in Britain, 42% of the coastline is hard rock, with many areas having cliffs behind the shore (Jackson & McIlvenny, 2011).

Light availability and water turbidity are principle factors in determining kelp depth range (Birkett et al. 1998b), with laminarians being reported to be able to withstand light levels of up to 1% surface irradiance. In Maine, USA, Saccharina latissima is abundant at both turbid and deep sites where surface irradiance averages 2.5% surface irradiance and has adapted to low-light conditions (Gerard, 1990).

This biotope IR.LIR.KVS.SlatPsaVS occurs on very sheltered and extremely sheltered infralittoral bedrock, boulders and cobbles (JNCC, 2015). Understanding how sea-level rise will affect tidal energy is fraught with uncertainty, although evidence appears to suggest that any alterations will be non-linear (Pickering et al., 2012, Li et al., 2016). Modelling potential outcomes of sea-level rise on the tidal and residual currents in the Bohai Sea, China showed effects were site-dependent, with energy either increasing or decreasing (Li et al., 2016). Similarly, Pickering et al. (2012) found a similar pattern around the UK for tidal amplitude.

Saccharina latissima occur in a wide range of water flow rates, from strong tidal currents to areas with low wave exposure (Norton, 1978; Birkett et al., 1998b). Psammechinus miliaris occurs in the subtidal and intertidal from coasts all around the British Isles but is typically found in more sheltered environments. It has a lower tolerance of wave exposure than Echinus esculentus and Paracentrotus lividus, the latter being found on the wave exposed shore. High levels of wave exposure are likely to limit the distribution of Psammechinus miliaris in the intertidal and subtidal (Dr Maeve Kelly, pers comm.). As Psammechinus miliaris feeds on a wide selection of algae and encrusting organisms (Lawrence, 1975) its distribution is thought to be limited more by physical parameters than food availability (Faller-Fritsch & Emson, 1972; cited in Lawrence, 1975). Therefore, an increase in wave exposure due to storminess is likely to remove at least a proportion of the population. 

Spirobranchus triqueter has been noted to occur in areas with very sheltered to exposed water flow rates (Price et al., 1980). Wood (1988) observed Spirobranchus sp. in strong tidal streams and Hiscock (1983) found that in strong tidal streams or strong wave action where abrasion occurs, fast-growing species such as Spirobranchus triqueter occur.

Corallina officinalis is an understorey, shade-tolerant algae. Reduced light attenuation is unlikely to affect Corallina officinalis except at the deepest extent of its distribution in subtidal populations. However, reduced light will probably reduce growth rates. Corallina officinalis thrives in exposed conditions where it may replace fucoids, although it is also found in sheltered conditions. In exposed conditions, it may grow as a cushion-like or compact turf (Irvine & Chamberlain 1994; Dommasnes 1968).

Sensitivity assessment.  There is likely to be considerable variation between sites, the relative contribution of wave surge and exposure to habitat suitability, and the depth range occupied by the biotope. Hence, it is difficult to assess the effect of the different sea-level rise scenarios. This biotope IR.LIR.KVS.SlatPsaVS can occur from the sublittoral fringe down to 10 m, although Saccharina latissima and Psammechinus miliaris are known to have a more extensive depth range, and as long as tidal currents or wave exposure did not become unfavourable as a result of sea-level rise, it is assumed at a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme emission scenario) might result in loss of some of the deeper extent of the biotope in some sites. This may be counteracted by landward migration of the biotope if suitable habitat is available. Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’. But resistance may be ‘Medium’ under the extreme emission scenario so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence,

High High Not sensitive
Q: Low
A: NR
C: NR
Q: High
A: High
C: High
Q: Low
A: Low
C: Low

Sea-level rise is occurring through a combination of thermal expansion and ice melt.  Sea levels have risen 1-3 mm/yr. in the last century (Cazenave & Nerem, 2004, Church et al., 2004, Church & White, 2006). Sea-level rise is expected to lead to substantial loss of intertidal habitats. Rocky shores backed by cliffs constitute about 80% of oceanic coastlines globally and in Britain, 42% of the coastline is hard rock, with many areas having cliffs behind the shore (Jackson & McIlvenny, 2011).

Light availability and water turbidity are principle factors in determining kelp depth range (Birkett et al. 1998b), with laminarians being reported to be able to withstand light levels of up to 1% surface irradiance. In Maine, USA, Saccharina latissima is abundant at both turbid and deep sites where surface irradiance averages 2.5% surface irradiance and has adapted to low-light conditions (Gerard, 1990).

This biotope IR.LIR.KVS.SlatPsaVS occurs on very sheltered and extremely sheltered infralittoral bedrock, boulders and cobbles (JNCC, 2015). Understanding how sea-level rise will affect tidal energy is fraught with uncertainty, although evidence appears to suggest that any alterations will be non-linear (Pickering et al., 2012, Li et al., 2016). Modelling potential outcomes of sea-level rise on the tidal and residual currents in the Bohai Sea, China showed effects were site-dependent, with energy either increasing or decreasing (Li et al., 2016). Similarly, Pickering et al. (2012) found a similar pattern around the UK for tidal amplitude.

Saccharina latissima occur in a wide range of water flow rates, from strong tidal currents to areas with low wave exposure (Norton, 1978; Birkett et al., 1998b). Psammechinus miliaris occurs in the subtidal and intertidal from coasts all around the British Isles but is typically found in more sheltered environments. It has a lower tolerance of wave exposure than Echinus esculentus and Paracentrotus lividus, the latter being found on the wave exposed shore. High levels of wave exposure are likely to limit the distribution of Psammechinus miliaris in the intertidal and subtidal (Dr Maeve Kelly, pers comm.). As Psammechinus miliaris feeds on a wide selection of algae and encrusting organisms (Lawrence, 1975) its distribution is thought to be limited more by physical parameters than food availability (Faller-Fritsch & Emson, 1972; cited in Lawrence, 1975). Therefore, an increase in wave exposure due to storminess is likely to remove at least a proportion of the population. 

Spirobranchus triqueter has been noted to occur in areas with very sheltered to exposed water flow rates (Price et al., 1980). Wood (1988) observed Spirobranchus sp. in strong tidal streams and Hiscock (1983) found that in strong tidal streams or strong wave action where abrasion occurs, fast-growing species such as Spirobranchus triqueter occur.

Corallina officinalis is an understorey, shade-tolerant algae. Reduced light attenuation is unlikely to affect Corallina officinalis except at the deepest extent of its distribution in subtidal populations. However, reduced light will probably reduce growth rates. Corallina officinalis thrives in exposed conditions where it may replace fucoids, although it is also found in sheltered conditions. In exposed conditions, it may grow as a cushion-like or compact turf (Irvine & Chamberlain 1994; Dommasnes 1968).

Sensitivity assessment.  There is likely to be considerable variation between sites, the relative contribution of wave surge and exposure to habitat suitability, and the depth range occupied by the biotope. Hence, it is difficult to assess the effect of the different sea-level rise scenarios. This biotope IR.LIR.KVS.SlatPsaVS can occur from the sublittoral fringe down to 10 m, although Saccharina latissima and Psammechinus miliaris are known to have a more extensive depth range, and as long as tidal currents or wave exposure did not become unfavourable as a result of sea-level rise, it is assumed at a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme emission scenario) might result in loss of some of the deeper extent of the biotope in some sites. This may be counteracted by landward migration of the biotope if suitable habitat is available. Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’. But resistance may be ‘Medium’ under the extreme emission scenario so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence,

High High Not sensitive
Q: Low
A: NR
C: NR
Q: High
A: High
C: High
Q: Low
A: Low
C: Low

Sea-level rise is occurring through a combination of thermal expansion and ice melt.  Sea levels have risen 1-3 mm/yr. in the last century (Cazenave & Nerem, 2004, Church et al., 2004, Church & White, 2006). Sea-level rise is expected to lead to substantial loss of intertidal habitats. Rocky shores backed by cliffs constitute about 80% of oceanic coastlines globally and in Britain, 42% of the coastline is hard rock, with many areas having cliffs behind the shore (Jackson & McIlvenny, 2011).

Light availability and water turbidity are principle factors in determining kelp depth range (Birkett et al. 1998b), with laminarians being reported to be able to withstand light levels of up to 1% surface irradiance. In Maine, USA, Saccharina latissima is abundant at both turbid and deep sites where surface irradiance averages 2.5% surface irradiance and has adapted to low-light conditions (Gerard, 1990).

This biotope IR.LIR.KVS.SlatPsaVS occurs on very sheltered and extremely sheltered infralittoral bedrock, boulders and cobbles (JNCC, 2015). Understanding how sea-level rise will affect tidal energy is fraught with uncertainty, although evidence appears to suggest that any alterations will be non-linear (Pickering et al., 2012, Li et al., 2016). Modelling potential outcomes of sea-level rise on the tidal and residual currents in the Bohai Sea, China showed effects were site-dependent, with energy either increasing or decreasing (Li et al., 2016). Similarly, Pickering et al. (2012) found a similar pattern around the UK for tidal amplitude.

Saccharina latissima occur in a wide range of water flow rates, from strong tidal currents to areas with low wave exposure (Norton, 1978; Birkett et al., 1998b). Psammechinus miliaris occurs in the subtidal and intertidal from coasts all around the British Isles but is typically found in more sheltered environments. It has a lower tolerance of wave exposure than Echinus esculentus and Paracentrotus lividus, the latter being found on the wave exposed shore. High levels of wave exposure are likely to limit the distribution of Psammechinus miliaris in the intertidal and subtidal (Dr Maeve Kelly, pers comm.). As Psammechinus miliaris feeds on a wide selection of algae and encrusting organisms (Lawrence, 1975) its distribution is thought to be limited more by physical parameters than food availability (Faller-Fritsch & Emson, 1972; cited in Lawrence, 1975). Therefore, an increase in wave exposure due to storminess is likely to remove at least a proportion of the population. 

Spirobranchus triqueter has been noted to occur in areas with very sheltered to exposed water flow rates (Price et al., 1980). Wood (1988) observed Spirobranchus sp. in strong tidal streams and Hiscock (1983) found that in strong tidal streams or strong wave action where abrasion occurs, fast-growing species such as Spirobranchus triqueter occur.

Corallina officinalis is an understorey, shade-tolerant algae. Reduced light attenuation is unlikely to affect Corallina officinalis except at the deepest extent of its distribution in subtidal populations. However, reduced light will probably reduce growth rates. Corallina officinalis thrives in exposed conditions where it may replace fucoids, although it is also found in sheltered conditions. In exposed conditions, it may grow as a cushion-like or compact turf (Irvine & Chamberlain 1994; Dommasnes 1968).

Sensitivity assessment.  There is likely to be considerable variation between sites, the relative contribution of wave surge and exposure to habitat suitability, and the depth range occupied by the biotope. Hence, it is difficult to assess the effect of the different sea-level rise scenarios. This biotope IR.LIR.KVS.SlatPsaVS can occur from the sublittoral fringe down to 10 m, although Saccharina latissima and Psammechinus miliaris are known to have a more extensive depth range, and as long as tidal currents or wave exposure did not become unfavourable as a result of sea-level rise, it is assumed at a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme emission scenario) might result in loss of some of the deeper extent of the biotope in some sites. This may be counteracted by landward migration of the biotope if suitable habitat is available. Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’. But resistance may be ‘Medium’ under the extreme emission scenario so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence,

Hydrological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
None High Medium
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Churchill & Moeller (1972) suggested the minimum temperature for the formation of reproductive structures in Codium fragile was 12-15°C. Haniask (1979) experimentally measured Codium fragile thalli and sporeling growth over a range of environmental conditions. Maximal thalli growth was recorded at 24°C.  The upper temperature threshold has been recorded at 30°C and no detectable growth occurs at <6°C.

Mortensen (1927) reported Psammechinus miliaris was found in Limfjorden, Denmark where winter water temperatures are regularly just above 0°C (Ursin, 1960). At Psammichinus miliaris southern range edge, Morocco and the Azores (Mortensen, 1927), winter-summer temperatures range from17-21°C (Seatemperature, 2015). The optimal temperature tolerances are therefore likely to be between 0-21°C. Furthermore Psammichinus miliaris reproduces in waters around the Faeroes where the summer temperatures seldom exceed 11°C (Ursin, 1960).

The temperature isotherm of 19-20°C has been reported as limiting Saccharina latissima geographic distribution (Müller et al., 2009). Gametophytes can develop in ≤23°C (Lüning, 1990) however, the optimal temperature range for sporophyte growth is 10-15°C (Bolton & Lüning, 1982). Bolton & Lüning (1982) experimentally observed that sporophyte growth was inhibited by 50-70% at 20°C and following 7 days at 23°C all specimens completely disintegrated. In the field Saccharina latissima has shown significant regional variation in its acclimation to temperature changes, for example Gerard & Dubois (1988) observed sporophytes of Saccharina latissima which were regularly exposed to ≥20°C could tolerate these temperatures, whereas sporophytes from other populations which rarely experience ≥17°C showed 100% mortality after 3 weeks of exposure to 20°C. Therefore the response of Saccharina latissima to a change in temperatures is likely to be locally variable.

Andersen et al. (2011) transplanted Saccharina latissima in the Skagerrak region, Norway and from 2006-2009. There was annual variation however high mortality occurred from August-November within each year of the experiment. In 2008 of the original 17 sporophytes 6 survived from March-September (approx. 65% mortality rate). All surviving sporophytes were heavily fouled by epiphytic organisms (estimated cover of 80 & 100%). Between 1960 and 2009, sea surface temperatures in the region have regularly exceeded 20°C and so has the duration which temperatures remain above 20°C. High sea temperatures has been linked to slow growth of Saccharina latissima which is likely to decrease the photosynthetic ability of, and increase the vulnerability of Saccharina latissima to epiphytic loading, bacterial and viral attacks (Anderson et al., 2011). These factors combined with establishment of annual filamentous algae in Skegerrak, Norway are likely to prevent the establishment of self sustaining populations in the area (Anderson et al., 2011; Moy & Christie, 2012).

Phyllophora crispa and Phyllophora pseudoceranoides are sensitive to large changes in temperature. Through culture experiments, 30°C was found lethal to Phyllophora pseudoceranoides within 4-12 weeks. At 27°C plants were severely damaged after 3 months but were able to recover when returned to lower temperatures.  Furthermore temperature was found to control the time at which Phyllophora pseudoceranoides begins sporulation. For example, ≥15°C sporulation occurred at 30 months were as 10°C sporulation occurred at 8 months (Molenaar & Breeman, 1994).

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are distributed throughout the UK (Connor et al., 2004). Northern to southern Sea Surface Temperature (SST) ranges from 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013)

Sensitivity assessment. A 2°C increase for one year may impair Saccharina latissima sporophyte growth but otherwise not affect the characterizing species.  A 5°C increase for one month combined with high UK summer temperatures may cause mortality in Saccharina latissima populations that are not acclimated to >20°C. Resistance has been assessed as ‘None’, to reflect the potential mass mortality effect of sudden temperature increases on Saccharina latissima, and resilience as ‘Medium’. Sensitivity has been assessed as ‘Medium’.

High High Not sensitive
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

During winter Codium spp. thalli reduce to a small holdfast and biological activity is reduced (Haniask, 1979). Mortensen (1927) reported Psammechinus miliaris was found in Limfjorden, Denmark where winter temperatures are regularly just above 0°C. Saccharina lattissima has a lower temperature threshold for sporophyte growth at 0°C (Lüning, 1990). Phyllophora pseudoceranoides can tolerate temperatures of -2 and 0°C 3 months (Molenaar & Breeman, 1994).  None of the characterizing species are likely to be adversely affected by a temperature decrease at the benchmark level.

Sensitivity assessment. Resistance has been assessed as ‘High’, resilience as ‘High’ and sensitivity as ‘Not sensitive’.

None Medium Medium
Q: Low
A: NR
C: NR
Q: High
A: Medium
C: High
Q: Low
A: Low
C: Low

Haniask (1979) reported Codium fragile salinity tolerances are variable and dependent on temperature. At 24°C thalli growth occurred from 12-42‰, with an optimum from 24-3 ‰. Gezelius (1962) reported the littoral growth form of Psammechinus miliaris had an optimal salinity range of 20-32 ppt, and the sub-littoral growth form had an optimal salinity tolerance of 26-38 ppt.

Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu. Saccharina latissima showed high photosynthetic ability at >80% of the control levels between 25-55 psu. The affect of long-term salinity changes (>5 days) or salinity >60 PSU on Saccharina latissima’ photosynthetic ability was not tested. Phyllophora crispa and Phyllophora pseudoceranoides are widely distributed around the UK in full marine conditions (Bunker et al., 2012).

Sensitivity assessment. IR.LIR.KVS.Cod, IR.LIR.KVSSlatPsaVS & IR.LIR.KVS.SlatPhyVS are only recorded from reduced or low salinity conditions (<18-30 psu). An increase to full salinity (30-40‰) may cause declines in Codium fragile growth. Phyllophora are recorded within full marine salinity, however, may not be sufficiently abundant or out-competed by other red seaweeds to dominate the habitat in full salinity. Therefore, a long-term change to full salinity (30-40‰) may change the character of the biotope, so that they are replaced by more diverse sheltered rock Saccharina latissima biotopes (e.g. IR.LIR.K.Slat). Resistance has been assessed as ‘None’, resilience as ‘Medium’. The sensitivity of this biotope to an increase in salinity has been assessed as ‘Medium’.

Low High Low
Q: Medium
A: High
C: High
Q: High
A: Medium
C: High
Q: Medium
A: Medium
C: High

Haniask (1979) reported that at 24 °C Codium fragile thalli growth could occur from 12-42 ‰, with an optimum from 24-30 ‰. 100% mortality occurred at 6 ‰ and at 12 ‰ growth was reduced. At the extremes of Codium fragile temperature tolerance (6 & 30°C) salinity tolerances were restricted, thalli grown at 6°C had a tolerance of 18-36 ‰, and thalli grown at 30 °C had a salinity tolerance of 18-48 ‰ (Haniask, 1979). Codium fragile sporlings had narrower salinity and thresholds than mature thalli; Spores did not germinate at <18 ‰.

Lindahl and Runnström (1929) showed (experimentally) that Psammechinus miliaris from the littoral (Z form) and sub-littoral (S form) had different salinity optima. Gezelius (1962) reported the littoral growth form had an optimal salinity range of 20-32 ppt, whereas the sub-littoral growth form 26-38ppt. Mature examples of the littoral growth form tolerated 15 ppt for a period of 27 days, however, were not able to produce gametes at this salinity.

Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu. Saccharina latissima showed high photosynthetic ability at >80 % of the control levels between 25-55 psu. Hyposaline treatment of 10-20 psu led to a gradual decline of photosynthetic ability. After 2 days at 5 psu, Saccharina latissima showed a significant decline in photosynthetic ability at approx. 30 % of control. After 5 days at 5 psu, Saccharina latissima specimens became bleached and showed signs of severe damage. The affect of long-term salinity changes (>5 days) or salinity >60 psu on Saccharina latissima’ photosynthetic ability was not tested. The experiment was conducted on Saccharina latissima from the Arctic, and at extremely low water temperatures (1-5 °C) macroalgae acclimation to rapid salinity changes could be slower than at temperate latitudes. It is, therefore, possible that resident Saccharina latissima of the UK maybe be able to acclimate to salinity changes more effectively.

Sensitivity assessment. IR.LIR.KVS.Cod is recorded in full salinity but probably exposed to reduced (18-30 ppt) conditions (Connor et al., 2004). A salinity decrease to “Low” (<18 ppt) may cause declines in Codium spp. growth and detriment the biotope. As a result, the Codium abundance could fall resulting in the SlatPhyVS biotope. IR.LIR.KVS.SlatPsaVS and IR.LIR.KVS.SlatPhyVS are recorded in ‘reduced’ and ‘low’ salinity, A further reduction in salinity would result in close to freshwater conditions and, however unlikely, would result in loss of the biotopes.  Resistance has been assessed as ‘Low’ and resilience as ‘High’. Therefore, the sensitivity of this biotope to a decrease in salinity has been assessed as ‘High’.

Medium High Low
Q: Low
A: NR
C: NR
Q: Medium
A: High
C: High
Q: Low
A: Low
C: Low

Information concerning the effects of increasing water flow on Codium spp. or Psammechinus miliaris is limited. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are predominantly recorded from sites with very weak to weak tidal streams (Connor et al., 2004).

Peteiro & Freire (2013) measured Saccharina latissima growth from 2 sites, the first had maximal water velocities of 0.3 m/sec and the second 0.1 m/sec. At site 1 Saccharina latissima had significantly larger biomass than at site 2 (16 kg/m to 12 kg/m respectively). Peteiro & Freire (2013) suggested that faster water velocities were beneficial to Saccharina latissima growth. However, Gerard & Mann (1979) found Saccharina latissima productivity is reduced in moderately strong tidal streams (≤1 m/sec) when compared to weak tidal streams (<0.5 m/sec). Despite the results published in Gerard & Mann (1979) Saccharina latissima can characterize or be a dominant in the tide swept biotopes IR.MIR.KT.XKTX & IR.MIR.KT.SlatT, which have been recorded from very strong (>3 m/sec) to moderately strong tidal streams (≤1 m/sec) (Connor et al., 2004), indicating Saccharina latissima can tolerate greater tidal streams than <1m/sec.

Sensitivity assessment. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are classed as low energy biotopes, restricted to only weak tidal streams. Many of the characteristic species are found in a range of tidal regimes so that a change in flow velocities of between 0.1-0.2 m/sec would not cause a significant effect on most species present. In SlatCod an increase in water flow at the benchmark may be enough to remove the silt that characterizes the biotope, and allow the abundance of Saccharina latissima to increase. In SlatPsa, an increase in water flow to moderately strong or strong would probably reduce the abundance of Echinus esculentus and to a lesser extent Psammechinus miliaris and favour a change from SlatPsaVS to SlatPhyVS. However, at the benchmark level, there is only likely to be slight changes in the character of the biotope and the KVS complex would remain.  Therefore, resistance has been assessed as ‘Medium’, resilience as ‘High’, and sensitivity has been assessed as ‘Low‘ at the benchmark level.

Low Medium Medium
Q: Low
A: NR
C: NR
Q: High
A: Low
C: High
Q: Low
A: NR
C: NR

IR.LIR.KVS.Cod , IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are predominantly shallow biotopes recorded from 0-10 m BCD An increase in emergence will result in an increased risk of desiccation and mortality of the macro-algae of the biotope.  Removal of canopy forming kelps, through desiccation, has also been shown to increase desiccation and mortality of the understorey macro-algae (Hawkins & Harkin, 1985). Thomsen & McGlathery (2007) demonstrated that Codium fragile biomass declined if artificially placed at higher tidal elevations, and would therefore likely be sensitive to changes in emergence regime. Many of the dominant species an also occur in the lower intertidal, however, the biotope would probably be replaced by a lower shore equivalent.  Providing that suitable substrata are present, the biotope is likely to re-establish further down the shore within a similar emergence regime to that which existed previously.

Sensitivity assessment. Resilience has been assessed as ‘Low’. Resistance as ‘Medium’. The sensitivity of this biotope to a change in emergence is considered as ‘Medium’.

High High Not sensitive
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are classed as low energy biotopes, recorded from sheltered-ultra wave sheltered sites (Connor et al., 2004). Therefore, a large scale increase in wave exposure is likely to have a fundamental effect on the characterizing species. However, evidence that specifically relates to the tolerance of the characterizing species to increases in wave exposure is limited.

Bulleri & Airoldi (2005) recorded the seasonal abundance of Codium fragile on the wave exposed and sheltered faces of breakwaters (coastal defence structures) built in the Adriatic sea. Codium fragile density was similar across both the exposed and sheltered sides in spring-early summer, however as summer progressed Codium fragile density declined on the exposed side of the breakwater. Codium fragile thalli also attained greater sizes (>14 cm) were more branched and had higher biomass on the sheltered faces of the breakwater. Indicating, that wave exposure has an impact on the density of Codium spp. thalli.

Little evidence on the effect of wave exposure on Psammechinus miliaris or Saccharina latissima was found, other than they are predominantly recorded in wave sheltered locations (Birkett et al., 1998; Kelly, 2000).

Sensitivity assessment. Wave exposure is one of the principal defining features of rock biotopes, and large changes in wave exposure are likely to alter the relative abundance of the dominant macro-algae, grazing and understorey community, and hence, the biotope. However, a change in near shore significant wave height of 3-5% is unlikely to have any significant effect on IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS or IR.LIR.KVS.SlatPsaVS. Resistance has been assessed as ‘High’, resilience as ‘High’ and sensitivity as ‘Not Sensitive’ at the benchmark level.

Chemical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

Bryan (1984) suggested that the general order for heavy metal toxicity in seaweeds is: organic Hg > inorganic Hg > Cu > Ag > Zn > Cd > Pb. Cole et al. (1999) reported that Hg was very toxic to macrophytes. The effects of copper, zinc and mercury on Saccharina latissima have been investigated by Thompson and Burrows (1984). They observed that the growth of sporophytes was significantly inhibited at 50 µg Cu /l, 1000 µg Zn/l and 50 µg Hg/l. Zoospores were found to be more intolerant and significant reductions in survival rates were observed at 25 µg Cu/l, 1000 µg Zn/l and 5 µg/l.

At the time of writing, little is known about the effects of heavy metals on echinoderms. Bryan (1984) reported that early work had shown that echinoderm larvae were intolerant of heavy metals, e.g. the intolerance of larvae of Paracentrotus lividus to copper (Cu) had been used to develop a water quality assessment. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu). Sea-urchins, especially the eggs and larvae, are used for toxicity testing and environmental monitoring (reviewed by Dinnel et al. 1988). Taken together with the findings of Gommez & Miguez-Rodriguez (1999) above it is likely that echinoderms are intolerant of heavy metal contamination.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

Saccharina latissima fronds, being predominantly subtidal, would not come into contact with freshly released oil but only to sinking emulsified oil and oil adsorbed onto particles (Birkett et al., 1998). The mucilaginous slime layer coating of laminariales may protect them from smothering by oil. Hydrocarbons in solution reduce photosynthesis and may be algicidal. However, Holt et al. (1995) reported that oil spills in the USA and from the 'Torrey Canyon' had little effect on kelp forests. Similarly, surveys of subtidal communities at a number sites between 1-22.5 m below chart datum showed no noticeable impacts of the Sea Empress oil spill and clean up (Rostron & Bunker, 1997). An assessment of holdfast fauna in Laminaria showed that although species richness and diversity decreased with increasing proximity to the Sea Empress oil spill, overall the holdfasts contained a reasonably rich and diverse fauna, even though oil was present in most samples (Somerfield & Warwick, 1999).

Echinoderms seem especially sensitive to the toxic effects of oil, likely because of the large amount of exposed epidermis (Suchanek, 1993). Schäfer & Köhler (2009) found 20 day exposure to sub-lethal concentrations of phenanthrene resulted in severe ovarian lesions of Psammechinus miliaris limiting the production of gametes.

Following the Torrey Canyon incident, large numbers of dead Psammechinus miliaris were found in the vicinity of Sennen, UK possibly due to exposure to the oil spill and the heavy spraying of hydrocarbon based dispersants in that area (Smith, 1968). Other significant effects have been observed in other species of urchins. For example, mass mortality of the echinoderm Echinocardium cordatum was observed shortly after the Amoco Cadiz oil spill (Cabioch et al., 1978) and reduced abundance of the species was detectable up to >1000 m away one year after the discharge of oil-contaminated drill cuttings in the North Sea (Daan & Mulder, 1996). In the Mediterranean around Naples, urchins were absent from areas which had visible signs of massive pollution of both sewage and oil. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gommez & Miguez-Rodriguez, 1999). But the observed effects may have been due to a single contaminant or synergistic effects of all present.

Cullinane et al. (1975) found large quantities of Codium fragile washed up on Relane, Bantry Bay, USA shortly after a large oil spill. No other evidence could be located for the effect of hydrocarbon & PAH contamination on Codium spp.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

Johansson (2009) exposed samples of Saccharina latissima to several antifouling compounds, observing chlorothalonil, DCOIT, dichlofluanid and tolylfluanid inhibited photosynthesis. Exposure to Chlorothalonil and tolylfluanid, was also found to continue inhibiting oxygen evolution after exposure had finished, and may cause irreversible damage. Smith (1968) noted that epiphytic and benthic red algae were intolerant of dispersant or oil contamination due to the Torrey Canyon oil spill; only the epiphytes Crytopleura ramosa and Spermothamnion repens and some tufts of Jania rubens survived together with Osmundea pinnatifida, Gigartina pistillata and Phyllophora crispa from the sublittoral fringe. Considerable observations and work, mainly on Echinus esculentus but also on Psammechinus miliaris (Smith, 1968; Gommez & Miguez-Rodriguez, 1999; Dinnel et al., 1988) indicate high intolerance to synthetic contaminants. Newton & McKenzie (1995) state that echinoderms tend to be very intolerant of various types of marine pollution, but there is little more detailed information than this. Following the Torrey Canyon incident, large numbers of dead Psammechinus miliaris in the vicinity of Sennen, UK presumably due to the heavy spraying of dispersants in that area and exposure to the oil spill (Smith, 1968).

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed.

Medium High Low
Q: Medium
A: High
C: High
Q: Medium
A: High
C: High
Q: Medium
A: High
C: High

Reduced oxygen concentrations can inhibit both photosynthesis and respiration in macroalgae (Kinne, 1977). Despite this, macroalgae are thought to buffer the environmental conditions of low oxygen, thereby acting as a refuge for organisms in oxygen depleted regions especially if the oxygen depletion is short-term (Frieder et al., 2012). A rapid recovery from a state of low oxygen is expected if the environmental conditions are transient. If levels do drop below 4 mg/l negative effects on these organisms can be expected, with adverse effects occurring below 2 mg/l (Cole et al., 1999).

Under hypoxic conditions, echinoderms become less mobile and stop feeding. The death of a bloom of the phytoplankton Gyrodinium aureolum in Mounts Bay, Penzance in 1978 produced a layer of brown slime on the sea bottom. This resulted in the death of fish and invertebrates, including Echinus esculentus, presumably due to anoxia caused by the decay of the dead dinoflagellates (Griffiths et al., 1979). Spicer (1995) investigated the effects of environmental hypoxia on the oxygen and acid-base status of Psammechinus miliaris. Oxygen uptake is not regulated by this species during progressive hypoxia. The habitat of this species includes rock pools on the shore that can experience quite severe hypoxia or even anoxia. Psammechinus miliaris must be able to tolerate low oxygen conditions provided the event is brief. In prolonged events, subtidal Psammechinus miliaris would presumably react in a similar fashion to the Echinus esculentus above.

Sensitivity Assessment. Reduced oxygen levels are likely to inhibit photosynthesis and respiration but not cause a loss of the macroalgae population directly. long-term de-oxygenation could, however, cause mortality in echinoderms. However, intertidal populations of Psammechinus miliaris are likely to be tolerant of hypoxia conditions. Resistance has been assessed as ‘Medium’, and resilience as ‘High’. Sensitivity has been assessed as ‘Low’.

Not relevant (NR) Not relevant (NR) Not sensitive
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009)  also highlighted that macroalgal communities are relatively tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009 and references therein).

Conolly & Drew (1985) found Saccharina latissima sporophytes had relatively higher growth rates when in close proximity to a sewage outlet in St Andrews, UK when compared to other sites along the east coast of Scotland. At St Andrews, nitrate levels were 20.22 µM, which represents an approx 25 % increase when compared to other comparable sites (approx 15.87 µM). Handå et al. (2013) also reported Saccharina latissima sporophytes grew approx 1 % faster per day when in close proximity to Norwegian Salmon farms, where elevated ammonium can be readily absorbed.  Read et al. (1983) reported after the installation of a new sewage treatment  works which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent.

Haniask (1979) observed that Codium fragile growth rate increased when exposed to elevated nitrogen (Nitrate, Nitrite, Ammonium and Urea). After 21 day nitrogen enrichment treatments Codium fragile grew on average 23-25 mm, whereas in the no enrichment treatment Codium fragile grew 4.8 mm. Conversely Thomsen & McGlathery (2006) observed that short-term nutrient enrichment did not increase the biomass of Codium fragile, however, the authors suggested that Codium spp. store excess Nitrogen to sustain growth if nutrients become depleted. Despite disagreement between the authors on the effect of enrichment, in both examples, enrichment did not have a detectable negative impact on Codium spp.

Sensitivity assessment. The evidence suggests that enrichment would not negatively impact on Codium spp. growth or directly affect Saccharina latissima. However indirectly nutrient enrichment may increase turbidity which may decrease water clarity and, therefore, macro-algae photosynthesis.Nevertheless, this biotope is considered to be Not sensitive at the pressure benchmark that assumes compliance with good status as defined by the WFD.

Medium High Low
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009) however also highlighted that macroalgal communities are relatively tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009 and references therein).

Conolly & Drew (1985) found Saccharina latissima sporophytes had relatively higher growth rates when in close proximity to a sewage outlet in St Andrews, UK when compared to other sites along the east coast of Scotland. At St Andrews, nitrate levels were 20.22 µM, which represents an approx 25 % increase when compared to other comparable sites (approx 15.87 µM). Handå et al. (2013) also reported Saccharina latissima sporophytes grew approx 1 % faster per day when in close proximity to Norwegian Salmon farms, where elevated ammonium can be readily absorbed.  Read et al. (1983) reported after the installation of a new sewage treatment  works which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent.

Sensitivity assessment. The evidence suggests that enrichment would not negatively impact on Codium spp. growth or directly affect Saccharina latissima. However, indirect organic enrichment may increase turbidity, which may decrease water clarity and therefore negatively affect macro-algae photosynthesis and growth. Resistance has therefore been assessed as ‘Medium’, resilience as ‘High’. Sensitivity has been assessed as ’Low’.

Physical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’).  Sensitivity within the direct spatial footprint of this pressure is, therefore, ‘High’.  Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

This biotope forms on hard rock substrata, i.e. bedrock, boulders and cobbles.  A change from hard rock to sedimentary substrata would result in permanent loss of the biotope. Therefore, resistance is assessed as None, resilience as Very low and sensitivity as High. Confidence is assessed as High due to the incontrovertible nature of the pressure.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant on hard rock substrata.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant on hard rock substrata.

None High Medium
Q: Low
A: NR
C: NR
Q: Medium
A: High
C: High
Q: Low
A: Low
C: Low

Abrasion of the substratum e.g. from bottom or pot fishing gear, cable laying etc. may cause localised mobility of the substrata and mortality of the resident community. The effect would be situation dependent however if bottom fishing gear were towed over a site it may mobilise a high proportion of the rock substrata and cause high mortality in the resident community. Sensitivity assessment. Resistance has been assessed as ‘None’, Resilience as ‘High’. Sensitivity has been assessed as ‘Medium’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Penetration is unlikely to be relevant to hard rock substrata. Therefore, the pressure is Not relevant.  However, physical disturbance of the surface is assessed under 'abrasion' above.

Medium High Low
Q: Medium
A: High
C: High
Q: High
A: Medium
C: High
Q: Medium
A: Medium
C: High

Suspended Particle Matter (SPM) concentration has a negative linear relationship with sub-surface light attenuation (Kd) (Devlin et al., 2008). An increase in SPM results in a decrease in sub-surface light attenuation. Light availability and water turbidity are principal factors in determining depth range at which kelp can be found (Birkett et al., 1998). Light penetration influences the maximum depth at which kelp species can grow and it has been reported that laminarians grow at depths at which the light levels are reduced to 1 percent of incident light at the surface. Maximal depth distribution of laminarians, therefore, varies from 100 m in the Mediterranean to only 6-7 m in the silt laden German Bight. In Atlantic European waters, the depth limit is typically 35 m. In very turbid waters the depth at which kelp is found may be reduced, or in some cases excluded completely (e.g. Severn Estuary), because of the alteration in light attenuation by suspended sediment (Lüning, 1990; Birkett et al., 1998).

Laminaria spp. show a decrease of 50 % photosynthetic activity when turbidity increases by 0.1/m (light attenuation coefficient  = 0.1-0.2/m; Staehr & Wernberg, 2009). An increase in water turbidity will likely decrease the photosynthetic ability of, abundance and density of Saccharina latissima. Codium fragile is photosynthetically efficient at low light levels (Ramus et al., 1976). Thomsen & McGlathery (2006) also demonstrated that Codium fragile gained biomass in both low and high light conditions, and found no apparent negative effect of shading on Codium fragile biomass. Psammechinus miliaris is omnivorous, feeding directly on live and dead algae but also on an array attached fauna (Kelly, 2000). The feeding plasticity of Psammechinus miliaris is likely to ameliorate some of the effects of diminished kelp growth as a result of decreased light availability, however, a decrease in Saccharina latissima may cause some declines in Psammechinus miliaris abundance.

Many red algal species are scour tolerant, and occur in turbid waters and in general algal turfs replace fucoids and kelps in areas where turbidity and sedimentation increase (Airoldi, 2003). Furthermore, many red algal species occur beneath canopies of larger macroalgae (e.g. IR.HIR.KFaR.LhypR) and are tolerant of low light levels (Gantt, 1990).

Sensitivity Assessment. A decrease in turbidity is likely to support enhanced growth (and possible habitat expansion) and is therefore not considered in this assessment. However, an increase in turbidity is likely to result in the loss of Saccharina latissima at the deeper extent of the biotope. Codium spp., Psammechinus miliaris and red algal species are resistant to decreases in water clarity. To represent the potential decline in Saccharina latissima resistance to this pressure has been defined as ‘Medium’ and resilience to this pressure is defined as ‘High’ at the benchmark level due to the scale of the impact. Hence, this biotope is regarded as having a sensitivity of ‘Low‘.

None High Medium
Q: Medium
A: Medium
C: High
Q: High
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium

Smothering by sediment e.g. 5 cm material during a discrete event, is unlikely to damage Saccharina latissima sporophytes but may affect holdfast fauna, gametophyte survival, interfere with zoospore settlement and, therefore, recruitment processes (Moy & Christie, 2012). Given the short life expectancy of Saccharina latissima (2-4 years-(Parke, 1948)), IR.LIR.KVS.SlatPhyVS is likely to be dependent on annual Saccharina latissima recruitment (Moy & Christie, 2012). Given the microscopic size of the gametophyte, 5 cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that kelp gametophytes can survive in darkness for between 6-16 months at 8°C and would probably survive smothering by a discrete event. Once returned to normal conditions the gametophytes resumed growth or maturation within 1 month (Dieck, 1993). Intolerance to this factor is likely to be higher during the peak periods of sporulation and/or spore settlement.

Mature Codium tomentosum thalli can grow up to 30 cm long (Pizzolla, 2007). Therefore, during summer when thalli are erect light deposition of sediment is unlikely to inundate thalli, however if sediment is deposited during winter when the thalli are fragmented and reduced to the holdfast (Haniask, 1979) then Codium spp. thalli will become inundated. It is unknown whether retained sediment would inhibit growth if the holdfast was inundated the following spring. Psammechinus miliaris is quite small (typically up to 4 cm) and is likely to be inundated by 5 cm of sediment (Jackson, 2008). If unable to 'dig out' of the sediment, deposited sediment may cause mortality.

The effect of deposition of 5 cm sediment Phyllophora crispa and Phyllophora pseudoceranoides is likely to be seasonally variable. As highlighted within the resilience section, Phyllophora sp. can lose fronds during winter. Phyllophora crispa fronds can grow to a length of 15cm and Phyllophora pseudoceranoides can grow to a length of 10cm (Bunker et al., 2012). Therefore, if plants are complete deposition is not likely to completely inundate mature individuals. However if sediment deposition occurs during periods of early seasonal thalli growth then this could affect Phyllophora sp. growth.

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are classed as low energy habitats, and are therefore unlikely to experience >moderate tidal streams (>0.5 m/sec) or wave action.

Sediment could, therefore, remain within the host habitat and recovery rate would be related to sediment retention but will probably be dissipated within a year. Deposited sediments could affect kelp recruitment (Birkett et al., 1998) and the survival of Psammechinus miliaris.

Sensitivity assessment. SlatCod is a heavily silted biotope (Connor et al., 2004) so an addition of 5 cm of fines may not have a significant effect on the biotope. In SlatPsaVS and SlatPhyV deposited fine sediment may remain for some time (depending on local conditions) and result in the smothering of small invertebrates, and smothering of short turf forming red algae and encrusting corallines.  Smothering would inhibit photosynthesis, growth for algae, and possibly lead to mortality of germlings. To reflect the potential effect that deposited sediment could have on Psammechinus miliaris. Resistance has been assessed as ‘None’, and resilience as ‘High’. Therefore, sensitivity has been assessed as ‘Medium’.

None Medium Medium
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: High

Smothering by sediment e.g. 30 cm material during a discrete event, is unlikely to damage Saccharina latissima sporophytes but may affect holdfast fauna, gametophyte survival, interfere with zoospore settlement and, therefore, recruitment processes (Moy & Christie, 2012). Given the short life expectancy of Saccharina latissima (2-4 years (Parke, 1948)), IR.LIR.KVS.SlatPhyVS is likely to be dependent on annual Saccharina latissima recruitment (Moy & Christie, 2012). Given the microscopic size of the gametophyte, 30cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that kelp gametophytes can survive in darkness for between 6-16 months at 8°C and would probably survive smothering by a discrete event. Once returned to normal conditions the gametophytes resumed growth or maturation within 1 month (Dieck, 1993). Intolerance to this factor is likely to be higher during the peak periods of sporulation and/or spore settlement.

Mature Codium tomentosum thalli can grow up to 30 cm long (MarLIN, 2015). Hence, 30 cm of deposited sediment is likely to inundate mature thalli. During winter, thalli fragment and individuals are reduced to a holdfast. It is unknown whether retained sediment would inhibit growth if the holdfast was inundated the following spring. Psammechinus miliaris is quite small (typically up to 40 mm) and is likely to be inundated by 30 cm of sediment (Jackson, 2008). If unable to 'dig out' of the sediment, deposited sediment may cause mortality. Phyllophora crispa fronds can grow to a length of 15 cm and Phyllophora pseudoceranoides can grow to a length of 10cm (Bunker et al., 2012). Deposition of 30 cm sediment is likely to completely inundate Phyllophora crispa and Phyllophora pseudoceranoides.

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are classed as low energy habitats, and are therefore unlikely to experience >moderate tidal streams (>0.5 m/sec) or wave action.  Sediment could, therefore, remain within the host habitat and recovery rate would be related to sediment retention but will probably be dissipated within a year. Deposited sediments could affect macroalgae recruitment (Birkett et al., 1998) and the survival of Psammechinus miliaris.

Sensitivity assessment Deposition of 30 cm of sediment is likely to inundate all but large macroalgae, e.g. mature Saccharina lattisima, and cause mortality in Codium spp. and understorey red seaweeds. As the deposit may remain for some time (depending on local conditions) and mortality is likely. Resistance has been assessed as of ‘None’; resilience has been assessed as ‘Medium’. Sensitivity has been assessed as ‘Medium’.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence.

Low Medium Medium
Q: Low
A: NR
C: NR
Q: Low
A: NR
C: NR
Q: Low
A: NR
C: NR

There is no evidence to suggest that anthropogenic light sources would affect macro-algae. Shading (e.g. by the construction of a pontoon, pier etc) could adversely affect IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS in areas where the water clarity is also low, and tip the balance to shade tolerant species, resulting in the loss of the biotope directly within the shaded area, or a reduction in seaweed abundance.

Sensitivity assessment. Resistance is probably 'Low', with a 'Medium' resilience and a sensitivity of 'Medium', albeit with 'low' confidence due to the lack of direct evidence.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant. This pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit the dispersal of spores.  But spore dispersal is not considered under the pressure definition and benchmark.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant. Collision from grounding vessels is addressed under abrasion above.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant.

Biological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
No evidence (NEv) No evidence (NEv) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Saccharina latissima has shown significant regional acclimation to environmental conditions. Gerard & Dubois (1988) found Saccharina latissima sporophytes which were regularly exposed to ≥20°C could tolerate these high temperatures whereas sporophytes from other populations which rarely experience ≥17 °C showed 100 % mortality after 3 weeks of exposure to 20°C. It is, therefore, possible that transplanted eco-types of Saccharina latissima may react differently to environmental conditions that differ from those of their origin.

However, there was little evidence for translocation of any other characteristic species over significant geographic distances. Nor was there any evidence regarding the genetic modification or effects of translocation.

Low Very Low High
Q: Low
A: NR
C: NR
Q: High
A: High
C: High
Q: Low
A: Low
C: Low

Competition with invasive macroalgae may be a potential threat to this biotope (de Bettignies et al., 2021).  Potential invasives include Undaria pinnatifida and Sargassum muticum.  Sargassum muticum is a circumglobal invasive species (Engelen et al., 2015).  It is recorded (2015) from Norway to Morocco and into the Mediterranean in the eastern Atlantic and from Alaska to Baja California in the eastern Pacific and from southern Russia to southern China in the western Pacific (Engelen et al., 2015).  It colonizes a variety of habitats and can tolerate -1°C to 30°C and survive salinities below 10 ppt.  Although fertilization does not occur below 15 ppt and growth of germlings is limited below 10°C it can complete its life cycle as long as temperatures are over 8°C for at least four months of the year (Engelen et al., 2015).  However, its distribution is limited by the availability of hard substratum (e.g. stones >10 cm) and light (Staeher et al., 2000; Strong & Dring, 2011; Engelen et al., 2015).  It is most abundant between 1 and 3 m below mean water.  But it has been recorded at 18 m or 30 m in the clear waters of California.  However, it is a poor competitor under low light and only develops dense canopies in shallow areas (Engelen et al., 2015).

Sargassum muticum was shown to replace and out-compete leathery, canopy-forming macroalgae such as Saccharina latissima, Halidrys siliquosa, and Fucus spp. and, to a lesser degree, understorey species such as Codium fragile, Chondrus crispus and Dictyota dichotoma in Limfjorden, Denmark between 1984 and 1997 (Staehr et al., 2000; Engelen et al., 2015; de Bettignies et al., 2021).  The invasion in Limfjorden had stabilized by 2005 although many of the native macroalgal species continued to decline (Engelen et al., 2015).  In Limfjorden, the distribution of Sargassum muticum was limited to areas with hard substratum, in particular stones > 10 cm in diameter, while smaller stones, gravel and sand were unsuitable.  It was most abundant between 1 and 4 m in depth but had low cover at 0-0.5 m or 4-6 m, in the turbid waters of the Limfjorden.  Limfjorden is wave sheltered although wave exposure has been reported to restrict the growth and survival of Sargassum muticum (Staehr et al., 2000).  Viejo et al. (1995) reported that Sargassum muticum transplanted to wave exposed shores in Spain experienced >80% breakages within a month and that the growth of undamaged plants was significantly lower than that of plants on sheltered shores.  Similarly, Andrew & Viejo (1998) noted that Sargassum muticum was restricted to intertidal rockpools in wave exposed sites in the Bay of Biscay.

Strong & Dring (2011) used canopy removal experiments to investigate inter- and intra-species competition between Sargassum muticum and Saccharina latissima in the Dorn, Strangford Lough, N. Ireland.  The Dorn consists of tidal pools, very sheltered from wave action but with moderately strong tidal streams (1-2 knots).  Sargassum muticum grew better in mixed stands with Saccharina latissima than in the highest density monospecific stands examined.  However, the growth of Saccharina was not affected by the proportion of Sargassum in mixed stands.  They concluded that Saccharina was not impacted significantly by the alien species while Sargassum benefited from growth in mixed stands.  Experimental manipulation of subtidal algal canopies in San Juan Islands, Washington State, USA, showed that Sargassum muticum reduced the abundance of native macroalgae, including the kelp Laminaria bongardiana due to shadingHowever, experimental removal of Sargassum resulted in the recovery of native species within about one year (Britton-Simmons, 2004; Engelen et al., 2015).  The negative effects of Sargassum muticum on native macroalgae are mainly due to competition for light, rather than changes in nutrient availability, sedimentation or water flow (Britton-Simmons, 2004; Engelen et al., 2015).  

Undaria pinnatifida (Wakame or Asian kelp) is a large brown seaweed and an Invasive Non-Indigenous Species (INIS) that could out-compete native UK kelp species (see Farrell & Fletcher, 2006; Thompson & Schiel, 2012; Brodie et al., 2014; Hieser et al., 2014; Arnold et al., 2016; Epstein & Smale, 2017; Epstein & Smale, 2018; Kraan, 2017; Epstein et al., 2019a,b; Tidbury, 2020).  Undaria pinnatifida originates from Japan but is established currently on the coastlines of New Zealand, Australia, Northern France, Spain, Italy, the UK, Portugal, Belgium, Holland, Argentina, Mexico, and the USA (De Leij et al., 2017).  Undaria pinnatifida was first recorded in the UK in the Hamble Estuary in 1994 (Macleod et al., 2016).  It has since proliferated along UK coastlines.  One year after its discovery at the Queen Anne Battery marina, Plymouth, it had become a major fouling plant on pontoons (Minchin & Nunn, 2014).  Although initially restricted to artificial habitats, such as marinas and ports, it is now widespread in natural habitats in several areas, including Plymouth Sound.

Undaria pinnatifida seems to settle better on artificial substrata (e.g. floats, marinas, or piers) than on natural rocky shores among local kelps (Vaz-Pinto et al., 2014).  It is found predominantly in low intertidal to shallow subtidal habitats (Epstein et al., 2019b) and is significantly more abundant on artificial substrata compared to natural rocky substrata (Heiser et al., 2014; Epstein & Smale, 2018).  James (2017) suggested that Undaria pinnatifida could out-compete native species on artificial substrata (such as marinas and wharf structures).  In Plymouth, UK, De Leij et al. (2017) found that natural habitats with dense native macroalgal canopies, such as Laminaria hyperborea, Laminaria ochroleuca, Laminaria digitata, and Saccharina latissima had more resistance to Undaria pinnatifida invasion than disturbed or sparse canopies, due to limited space and light availability for Undaria pinnatifida recruits. However, the dense canopies did not always prevent the invasion of Undaria pinnatifida as sporophytes were still recorded within dense Laminaria canopies, so canopy disturbance was not always required (De Leij et al., 2017; Epstein & Smale, 2018).

Undaria pinnatifida species behaves as a winter annual and recruitment occurs in winter followed by rapid growth through spring, maturity, and then senescence through summer, with only the microscopic life stages persisting through autumn.  It exhibits multiple dispersal strategies, such as short-range spore dispersal, and long-range dispersal as whole drift plants or fragments.  Undaria pinnatifida has spread rapidly across the UK and Europe, resulting in community-wide responses and impacts (Vaz-Pinto et al., 2014; Epstein & Smale, 2017).  Its impacts are complex and context-specific, depending on space, time, and taxa present in the introduced location (Epstein & Smale, 2017; Teagle et al., 2017; Tidbury, 2020).

Undaria pinnatifida has a wide physiological niche meaning it can occur in both coastal and estuarine environments showing tolerance for varying salinities, turbidity, and siltation (Heiser et al., 2014; Epstein & Smale, 2018).  Undaria pinnatifida can inhibit a broad range of habitats including – reefs; coastal brackish/saline lagoons; large shallow inlets and bays; estuaries; estuarine rocky habitats; natural or near-natural estuary; coastal lagoons; and tidal rivers, estuaries, mudflats, sandflats and lagoons (James, 2017).  Undaria pinnatifida prefers sites sheltered with low wave exposure and weak tidal streams (Heiser et al., 2014; Epstein & Smale, 2018).  In natural habitats, Undaria pinnatifida was not recorded if the wave fetch was greater than 642 km but increased in abundance and cover in very sheltered sites (Epstein & Smale, 2018).  Undarai sporophytes were also reported to survive at salinities down to 11 psu (Epstein & Smale, 2018).

In Plymouth Sound (UK), Epstein et al. (2019b) found that within its depth range (+1 to –4 m), Undaria pinnatifida co-existed with seven species of canopy-forming brown macroalgae, including Saccharina latissima.  However, they reported that Undaria pinnatifida biomass was negatively related to Saccharina latissima in both intertidal and subtidal habitats. This was only statistically significant in subtidal habitats, which suggested that there was some competition between the two species (Epstein et al., 2019b). Heiser et al. (2014) surveyed 17 sites within Plymouth Sound, UK and found that Saccharina latissima was significantly more abundant at sites with Undaria pinnatifida with ca 5 Saccharina latissima individuals present per m², compared to ca 0.5 Saccharina latissima individuals per m² present at sites without Undaria pinnatifida.

Undaria pinnatifida has been reported to both co-exist with and out-compete Saccharina latissima (Farrell & Fletcher, 2006; Heiser et al., 2014; Epstein et al., 2019b). For example, in Torquay Marina, UK, Farrell & Fletcher (2006) completed a canopy removal experiment between 1996-2002. They reported that Saccharina latissima decreased in both control and treatment plots from ca 3 plants per 0.45 m² in 1996 to ca 1 plant per 0.45 m² in 1997 and had disappeared completely from pontoons by 2002.  This coincided with a significant increase in Undaria pinnatifida from zero plants per 0.45 m² in 1996 to ca 6 plants per 0.45 m² in 1997.  However, there was a slight decrease in Undaria pinnatifida in both control and treatment plots between 1997 and 1998.  By 2002, Undaria pinnatifida had recovered at control and treatment plots to ca 4-6 plants per 0.45 m² whereas Saccharina latissima had not.

Undaria pinnatifida was successfully eradicated on a sunken ship in Clatham Islands, New Zealand, by applying a heat treatment of 70°C (Wotton et al., 2004).  However, numerous other eradication attempts have failed and, as noted by Fletcher & Farrell (1998), once established Undaria pinnatifida resists most attempts at long-term removal.

The proliferation of Undaria pinnatifida and competition with native species may cause a reduction in local biodiversity (Valentine & Johnson, 2003; Vaz-Pinto et al., 2014; Arnold et al., 2016; Teagle, 2017; Tidbury, 2020).  A shift towards Undaria pinnatifida dominated beds could result in diminished epibiotic assemblages and lower local biodiversity compared with assemblages associated with native perennial kelp species, such as Laminaria spp. and Saccharina latissima (Arnold et al., 2016; Teagle et al., 2017).  In Plymouth, UK, Arnold et al. (2016) found that Undaria pinnatifida supported less than half the number of taxa and had no unique epibionts compared to Laminaria ochroleuca and Saccharina latissima (Arnold et al., 2016).

Sensitivity assessment.  The above evidence suggests that both Sargassum muticum and Undaria pinnatifida can both compete with and co-exist with Saccharina latissima, depending on local conditions.  For example, Undaria pinnatifida can out-compete Saccharina latissima in artificial habitats, such as in Torquay Marina, but within natural habitats, it can co-exist with native kelp species within its depth range (-1 to 4 m), as shown in Plymouth Sound, UK.  Similarly, Sargassum muticum out-competed Saccharina latissima in theLimfjorden but coexisted in the Dorn in Strangford Lough.

This Saccharina latissima dominated biotope (IR.LIR.KVS.SlatPsaVS) is found from 0 to 10 m in depth (JNCC, 2015, 2022) in reduced or low salinity with weak or very weak tidal streams and very or extremely wave sheltered conditions.  The evidence above suggests that Undaria prefers sheltered conditions, with low tidal flow, in the shallow subtidal and sublittoral fringe (ca +1 to 4 m in depth), while Sargassum also prefers wave sheltered conditions and shallow water (ca 1 to 4 m depth). Both species are reported to survive in estuarine conditions and low salinities. Therefore, Undaria pinnatifida and Sargassum muticum are only likely to threaten the most shallow (e.g. 0-5 m) examples of this biotope, where suitable hard substrata are available.  They may either co-exist with or out-compete Saccharina latissima, resulting in a potentially significant (25-75%) reduction in the abundance or extent of the native kelp and a possible decrease in the diversity of other macroalgae.  Therefore, resistance is assessed as ‘Low’ for shallow, wave sheltered examples of the biotope, i.e. above 5 m in depth.  Both Sargassum and Undaria may colonize at 5-10 m but in low numbers so Saccharina will probably dominate.  Recovery after invasion by Sargassum or Undaria, although rapid, would require direct intervention (removal) so that resilience is assessed as ‘Very low’.  Hence, the sensitivity of shallow, sheltered, examples of the biotope is assessed as ‘High’.  Overall, confidence is assessed as ‘Low’ due to evidence of variation and site-specific nature of competition between native kelps, Sargassum muticum, and Undaria pinnatifida.

Medium High Low
Q: Medium
A: High
C: Medium
Q: Low
A: NR
C: NR
Q: Medium
A: NR
C: NR

Saccharina latissima may be infected by the microscopic brown alga Streblonema aecidioides. Infected algae show symptoms of Streblonema disease, i.e. alterations of the blade and stipe ranging from dark spots to heavy deformations and completely crippled thalli (Peters & Scaffelke, 1996). Infection can reduce growth rates of host algae.

Psammechinus miliaris is susceptible to 'Bald-sea-urchin disease', which causes lesions, loss of spines, tube feet, pedicellariae, destruction of the upper layer of skeletal tissue and death (Maes et al., 1986). It is thought to be caused by the bacteria Vibrio anguillarum and Aeromonas salmonicida. This disease has been recorded from Psammechinus miliaris from the French Atlantic coast. Although associated with mass mortalities of Strongylocentrotus franciscanus in California and Paracentrotus lividus in the French Mediterranean there is no evidence of mass mortalities of Psammechinus miliaris associated with this disease around Britain and Ireland.

Sensitivity assessment. Resistance to the pressure is considered ‘Medium’, and resilience ‘High’. The sensitivity of this biotope to the introduction of microbial pathogens is assessed as ‘Low’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Targeted removal of characterizing species IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS would likely have a fundamental effect on the character of the biotopes. Saccharina latissima is commercially cultivated, however, typically sporophytes are matured on ropes (Handå et al., 2013) and not directly extracted from the seabed, as is the case with Laminaria hyperborea (see Christie et al., 1998).  As a consequence related literature on which to assess the “resistance” of Saccharina latissima to targeted harvesting is sparse. Similarly, no evidence was found to suggest that Codium spp. was extracted for commercial or recreational purposes.  Psammechinus miliaris is targeted as a potential aquaculture species. When fed a nutritious diet in culture, the gonad biomass rapidly proliferates which can then be marketed as urchin “roe” (Kelly et al., 1998; 2000). However, Kelly (2000) concluded that there was no viability in a Psammechinus miliaris commercial fishery because of the low gonad content of wild populations. While some extraction of Psammechinus miliaris may conceivably develop for roe-enhancement through feeding artificial or nutrient enriched diets (Dr Maeve Kelly pers comm, 2000), this is currently not in practice within the UK.

Sensitivity assessment.  None of the characterizing species are commercially extracted from the seabed. If extracted in the future resistance would need to be re-assessed. This pressure has been assessed as ‘Not relevant’.

Low High Low
Q: Low
A: NR
C: NR
Q: High
A: High
C: High
Q: Low
A: Low
C: Low

Direct, physical impacts from harvesting are assessed through the abrasion and penetration of the seabed pressures. The sensitivity assessment for this pressure considers any biological/ecological effects resulting from the removal of non-target species on this biotope.  Incidental removal of the key characterizing species and associated species would alter the character of the biotope. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are characterized by a canopy of Saccharina lattisima. Saccharina lattisima provides a canopy under which a variety of red seaweeds grow, includingPhyllophora sp. (as in IR.LIR.KVS.SlatPhyVS).The loss of the canopy due to incidental removal as by-catch would, therefore, alter the character of the habitat and result in the loss of species richness. The ecological services such as primary and secondary production provided by these species would also be lost. Codium spp. is also a key/characterizing species that may be removed through incidental/accidental by-catch. Removal Codium spp. would by definition also change biotope structure

Psammechinus miliaris may suffer as a result of trawling or dredging for other benthic species. Species with fragile tests such as urchins have been reported to be particularly sensitive to damage from mobile fishing gear (see Jennings & Kaiser, 1998; Bergman & van Santbrink, 2000). Kaiser & Spencer (1994) reported a ca 20 – 50% mortality in Psammechinus miliaris as a result of a single pass of an experimental 4 m beam trawl.

Sensitivity assessment. For this assessment, it has been assumed that incidental removal would result in complete removal of the characterizing species. Resistance has been assessed as Low, resilience as ‘High’ and sensitivity as ‘Low’.

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Citation

This review can be cited as:

Stamp, T.E., Williams, E., Mardle, M.J., & Lloyd, K.A., 2022. Saccharina latissima and Psammechinus miliaris on variable salinity grazed infralittoral rock. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27-01-2023]. Available from: https://www.marlin.ac.uk/habitat/detail/359

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Last Updated: 23/06/2022