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information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Silted cape-form Laminaria hyperborea on very sheltered infralittoral rock

08-11-2016

Summary

UK and Ireland classification

UK and Ireland classification

Description

Cape-form of the kelp Laminaria hyperborea on very silted rock, particularly in extremely sheltered sealochs of western Scotland. Below the huge kelp fronds (which often trail onto the seabed) foliose seaweeds form a silted understorey on the rock including Phycodrys rubens, Delesseria sanguinea, Cryptopleura ramosa and Plocamium cartilagineum as well as coralline crusts. At some sites the filamentous red seaweed Bonnemaisonia hamifera, Heterosiphonia plumosa and Brongniartella byssoides may carpet the seabed. Ascidians, particularly Ascidiella aspersa, Ascidia mentula, Ciona intestinalis and Clavelina lepadiformis thrive well in these conditions. The echinoderms Antedon bifida, Echinus esculentus and Asterias rubens are often present along with the gastropod Gibbula cineraria. An abundant growth of the hydroid Obelia geniculata can cover the silted kelp fronds along with the bryozoan Membranipora membranacea. The anthozoan Caryophyllia smithii can be present among the kelp holdfasts. The tube-building polychaete Spirobranchus triqueter can be present on the rock surface along with the crab Necora puber. This biotope generally occurs on shallow bedrock or boulder slopes or isolated rocks protruding through muddy sediment (see Connor et al., 2004).

Depth range

0-5 m, 5-10 m

Additional information

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Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

IR.LIR.K.LhypCape is defined by abundant growth of the cape-form of Laminaria hyperborea. Below the kelp fronds, red seaweeds such as Phycodrys rubens, Delesseria sanguinea, Cryptopleura ramosa and Plocamium cartilagineum form a silted understory. An abundant growth of the hydroid Obelia geniculata and bryozoan Membranipora membranacea can cover the silted kelp fronds. This biotope is often present on rocky outcrops surrounded by muddy sediments in extremely sheltered to sheltered wave exposure, such as Scottish sea lochs or Irish sea loughs. Solitary ascidians such as Ascidiella aspersa, Ascidia mentula, Ciona intestinalis and Clavelina lepadiformis can also thrive in this habitat, however these species can also be found on deeper, nearby rock, beyond the limit of foliose seaweeds, and are therefore not thought of as defining species in IR.LIR.K.LhypCape.

The cape-form of Laminaria hyperborea (Laminaria hyperborea f. cucullata) is a growth form of Laminaria hyperborea, described by Svendsen & Kain (1971) The cape-form Laminaria hyperborea has a poorly developed and weak holdfast. The stipe is bent/twisted and short, normally less than 50 cm long. The frond is thin (Sjøtun et al., 1998), brittle and easily torn, heart shaped at the base, undivided and broad, forming a draping “cape” or “apron” over the rock (Svendsen & Kain 1971).  IR.LIR.K.LhypCape is recorded from ca 0-20 m below chart datum, typically on heavily silted rocky outcrops within sheltered-extremely sheltered habitats, e.g. Scottish sea lochs or Irish sea loughs (Svendsen & Kain, 1971; Connor et al., 2004). While the geographic distribution of cape-form Laminaria hyperborea is documented within the UK (Connor et al., 2004) only one reference (Svendsen & Kain 1971) comprehensively describes it’s morphology and vertical/depth distribution. Despite the relative scarcity of information covering cape-form Laminaria hyperborea, much is known on the life history (Kain & Jones, 1964; Christie et al., 1998) and recovery (Kain, 1975; Christie et al., 1998) of Laminaria hyperborea in wave exposed biotopes (e.g. IR.HIR.KFaR.LhypR). Inferences can therefore be made on the likely effect of the pressures assessed within this review on cape-form Laminaria hyperborea and hence the habitat structure of IR.LIR.K.LhypCape. Where possible references to cape-form Laminaria hyperborea’ distinctive features have been made throughout this review.

In undertaking this assessment of sensitivity, account is taken of knowledge of the biology of all characterizing species/taxa in the biotope. However, 'indicative species' are particularly important in undertaking the assessment. For this sensitivity assessment the cape-form of Laminaria hyperborea is the key characteristic and structural species, and hence the primary focus of research, however it is recognized that the understory red seaweed community also define the biotope. Examples of important species groups are mentioned where appropriate.

Information on the cape-form Laminaria hyperborea is limited. However, where information was lacking inferences were made from typical growth form Laminaria hyperborea references from exposed biotopes e.g. IR.HIR.Kfar.LhypR.  Please note that Laminaria digitata can also form a ‘cape’ form (Laminaria digitata f. cucullata).  Therefore, it is possible that records of the ‘cape-form’ in this biotope may describe either species.  However, in the absence of a definitive survey records, the following review assumes that only Laminaria hyperborea is present.

Resilience and recovery rates of habitat

Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is found from ca 4-25 m Below Chart Datum (BCD) (Svendsen & Kain, 1971; Connor et al., 2004). Svendsen & Kain (1971) conducted a transplantation experiment to observe if cape-form fronds (of cape-form Laminaria hyperborea) were a phenotypic response of Laminaria hyperborea to low water movement. At a sheltered location in southern Norway, six cape-form Laminaria hyperborea were transplanted from 15 m BCD to 0.5 m BCD and ten Laminaria hyperborea vice versa.  After six months none of the cape-form Laminaria hyperborea had survived at 0.5 m and only their holdfasts were still present. Of the ten Laminaria hyperborea transplanted to 15 m BCD, four survived and produced cape-form fronds. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Svendsen & Kain (1971) suggested increased wave action at 0.5 m was the reason why none of the cape-form Laminaria hyperborea survived beyond six months. Although the wave exposure at the site was not formally tested, this evidence suggests that cape-form Laminaria hyperborea is highly sensitive to physical disturbance e.g. from water movement (wave action and/or tidal movement).

A number of review and experimental publications have assessed the recovery of Laminaria hyperborea beds and the associated community within high energy habitats (e.g. IR.HIR.KFaR.LhypR). If environmental conditions are favourable Laminaria hyperborea can recover following disturbance reaching comparable plant densities and size to pristine Laminaria hyperborea beds within 2-6 years (Kain, 1979; Birkett et al., 1998; Christie et al., 1998). Holdfast communities may recover in 6 years (Birkett et al., 1998). Full epiphytic community and stipe habitat complexity regeneration requires over 6 years (possibly 10 years) (Christie et al., 1998). These recovery rates were based on observations of discrete kelp harvesting events, recurrent disturbance occurring frequently within 2-6 years of the initial disturbance is likely to lengthen recovery time (Birkett et al., 1998, Burrows et al., 2014). Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared, however, within 2 years of clearance the blocks were dominated by Laminaria hyperborea.

Laminaria hyperborea has a heteromorphic life strategy, A vast number of zoospores (mobile asexual spores) are released into the water column between October-April (Kain & Jones, 1964). Zoospores settle onto rock substrata and develop into dioecious gametophytes (Kain, 1979) which, following fertilization, develop into sporophytes and mature within 1-6 years (Kain, 1979; Fredriksen et al., 1995; Christie et al., 1998). Siltation within IR.LIR.K.LhypCape may provide a physical barrier to Laminaria hyperborea zoospore settlement, recurrent siltation may also decrease light and therefore decrease gametophyte survival. Dieck (1993) demonstrated that Laminaria hyperborea gametophytes can survive in darkness for between 6 -16 months at 8°C, however Kain (1964) demonstrated that gametophyte survival rate and sporophyte development dramatically decreases beyond 10 days of darkness. Heavy deposition of sediment/siltation could therefore significantly inhibit recruitment pathways and therefore recovery of IR.LIR.K.LhypCape following disturbance. Laminaria hyperborea zoospores have a recorded dispersal range of ca 200 m (Fredriksen et al., 1995). However, zoospore dispersal is greatly influenced by water movements, plus 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).

The nature of Laminaria hyperborea biotopes are partially reliant on low (or no) populations of sea urchins, primarily the species; Echinus esculentus, Paracentrotus lividus and Strongylocentrotus droebachiensis, which graze directly on macroalgae, epiphytes and the understory community. 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 create 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 (Steneck et al., 2002, Norderhaug & Christie, 2009). Continued intensive urchin grazing pressure on Laminaria hyperborea biotopes can inhibit the Laminaria hyperborea recruitment (Sjøtun et al., 2006) and cause urchin barrens to persist for decades (Cristie et al., 1998; Stenneck et al., 2004; Rinde & Sjøtun, 2005). The mechanisms that control sea urchin aggregations are poorly understood but have been attributed to anthropogenic pressure on top down urchin predators (e.g. cod or lobsters).  While these theories are largely unproven a number of studies have shown removal of urchins from grazed areas coincide with kelp re-colonization (Lienaas & Christie, 1996; Nourderhaug & Christie, 2009).  Lienaas & Christie, (1996) removed Strongylocentrotus droebachiensis from “Urchin Barrens” and observed a succession effect, in which the substratum was initially colinized by filamentous macroalgae and Saccharina latissima, however after 2-4 years Laminaria hyperborea dominated the community.

Reports of large scale urchin barrens within the North East Atlantic are generally limited to regions of the North Norwegian and Russian Coast (Rinde & Sjøtun, 2005, Nourderhaug & Christie, 2009). Within the UK, urchin grazed biotopes (IR.MIR.KR.Lhyp.GzFt/Pk, IR.HIR.KFaR.LhypPar, IR.LIR.K.LhypLsac.Gz & IR.LIR.K.Lsac.Gz) are generally localised to a few regions in North Scotland and Ireland (Smale et al., 2013; Stenneck et al., 2002; Norderhaug & Christie 2009; Connor et al., 2004). IR.MIR.KR.Lhyp.GzFt/Pk, IR.HIR.KFaR.LhypPar, IR.LIR.K.LhypLsac.Gz & IR.LIR.K.Lsac.Gz are characterized by a canopy forming kelp. However, urchin grazing decreases the abundance and diversity of understory species. In the Isle of Man. Jones & Kain (1967) observed low Echinus esculentus grazing pressure can control the lower limit of Laminaria hyperborea and remove Laminaria hyperborea sporelings and juveniles. Urchin abundances in ‘urchin barrens’ have been reported as high as 100 individuals/m2 (Lang & Mann, 1978). Kain (1967) reported urchin abundances of 1-4/m2 within experimental plots of the Isle of Man. Therefore while ‘urchin barrens’ are not presently an issue within the UK, relatively low urchin grazing has been found to control the depth distribution of Laminaria hyperborea, negatively impact on Laminaria hyperborea recruitment and reduce the understory community abundance and diversity.

Other factors that are likely to influence the recovery of Laminaria hyperborea biotopes is competitive interactions with Invasive Non Indigenous Species (INIS), e.g. Undaria pinnatifida (Smale et al., 2013; Brodie et al., 2014; Heiser 2014), and/or the Lusitanian kelp Laminaria ochroleuca (Brodie et al., 2014; Smale et al., 2014). A predicted sea temperature rise in the North and Celtic seas of between 1.5-5°C over the next century (Philippart et al., 2011) is likely to create northward range shifts in many macroalgal species, including Laminaria hyperborea. Laminaria hyperborea is a northern (Boreal) kelp species, thus increases in seawater temperature is likely to affect the resilience and recoverability of Laminaria hyperborea biotopes with southerly distributions in the UK (Smale et al., 2013; Stenneck et al., 2002). Evidence suggests that the Lustanian kelp Laminaria ochroleuca (Smale et al., 2014), and the INIS Undaria pinnatifida (Heiser et al., 2014) are competing with Laminaria hyperborea along the UK south coast and may displace Laminaria hyperborea from some sub-tidal rocky reef habitats. The wider ecological consequences of Laminaria hyperborea’ competition with Laminaria ochroleuca and Undaria pinnatifida are however as of yet unknown.

Resilience assessment.  Sparse evidence is available to assess resilience of cape-form Laminaria hyperborea to the pressures assessed within this review. Svendsen & Kain (1971) suggests the cape-form is highly sensitive to physical disturbance and high siltation within IR.LIR.K.LhypCape could extend recovery of the habitat when compared to exposed Laminaria hyperborea biotopes (e.g. IR.HIR.KFaR.LhypR). Available evidence from exposed Laminaria hyperborea biotopes suggests that if cape-form Laminaria hyperborea were removed from the substratum, e.g. through physical disturbance, Laminaria hyperborea could re-establish dominance in the habitat within a period of 2-6 years (Kain 1975; Birkett et al., 1998; Christie et al., 1998), and the associated community within 7-10 years (Christie et al., 1998). However, other factors such as competition interactions with Laminaria ochroleuca and Undaria pinnatifida may limit recovery of Laminaria hyperborea following disturbance. Also, urchin grazing pressure may negatively affect Laminaria hyperborea recruitment and reduce the diversity and abundance of the understory community. The resilience of IR.LIR.K.LhypCape has been assessed as Medium.

Heavy siltation could extend the recovery period of cape-forming Laminaria hyperborea however the effect of siltation on Laminaria hyperborea recovery is not directly quantified and therefore recovery rates from exposed Laminaria hyperborea biotopes has been used within this review.  Urchin grazing pressure could extend recovery/resilience of the Laminaria hyperborea biotopes to over 25 years, if urchin grazing of the same scale as observed in Northern Norway occurred within the UK resilience would be re-assessed as Very Low. However, because of the limited/localised incidence of urchin grazing within the UK urchin grazing on large scales has not been included in this general resilience assessment. Introduction of Invasive Non Indigenous species (INIS) could also inhibit the recovery of Laminaria hyperborea biotopes for an indeterminate amount of time, in these cases resilience would need to be re-assessed as 'Very low'. Another factor that is beyond the scope of this sensitivity assessment is the presence of multiple concurrent synergistic or cumulative effects, which Smale et al. (2013) suggests could be more damaging than the individual pressures.

Hydrological Pressures

 ResistanceResilienceSensitivity
Medium Medium Medium
Q: Medium
A: High
C: High
Q: High
A: High
C: High
Q: Medium
A: High
C: High

Kain (1964) stated that Laminaria hyperborea sporophyte growth and reproduction could occur within a temperature range of 0-20°C. Upper and lower lethal temperatures have been estimated at between 1 -2°C above or below the extremes of this range (Birkett et al., 1988). However, above 17°C gamete survival is reduced (Kain, 1964; 1971) and gametogenesis is inhibited at 21°C (Dieck, 1992). It is therefore likely that Laminaria hyperborea recruitment will be impaired at a sustained temperature increase of above 17°C. Sporophytes however can tolerate slightly higher temperatures of 20°C. Temperature tolerances for Laminaria hyperborea are also seasonally variable and temperature changes are less tolerated in winter months than summer months (Birkett et al., 1998).

Subtidal red algae are less tolerant of temperature extremes than intertidal red algae, surviving between -2°C and 18-23°C (Lüning 1990; Kain & Norton, 1990). Temperature increase may affect growth, recruitment or interfere with reproduction processes. For example, there is some evidence to suggest that blade growth in Delesseria sanguinea is delayed until ambient sea temperatures fall below 13°C. Blade growth is also likely to be intrinsically linked to gametangia development (Kain, 1987), maintenance of sea temperatures above 13°C may affect recruitment success.

IR.LIR.K.LhypCape is distributed along the west coast of the UK from Orkney to South West Ireland; however records are concentrated in the North West of Scotland (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).

The available evidence suggests that combined with southern sea temperatures an increase of temperature of 5°C over a period of 1 month would not inhibit recruitment, however may be outside of the optimal range for spore production and/or settlement as well as negatively affect sporophyte growth. An increase in 2°C over a period of a year may similarly negatively affect Laminaria hyperborea recruitment processes in southern biotopes. Northern examples of IR.LIR.K.LhypCape (where most records are concentrated) are unlikely to be affected at the benchmark level.

Sensitivity assessment. Overall, a chronic change (2°C for a year) outside normal range for a year may reduce recruitment and growth, resulting in a minor loss in the population of kelp, especially in winter months or in southern examples of the biotope. However, an acute change (5°C for a month; e.g. from thermal effluent) may result in loss of abundance of kelp or extent of the bed, especially in winter. Therefore, resistance to the pressure is considered ‘Medium’, and resilience ‘Medium’. The sensitivity of this biotope to increases in temperature has been assessed as ‘Medium’.

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

Kain (1964) stated that Laminaria hyperborea sporophyte growth and reproduction could occur within a temperature range of 0 -20°C. Upper and lower lethal temperatures have been estimated at between 1-2°C above or below the extremes of this range (Birkett et al., 1988). Subtidal red algae can survive at temperatures between -2°C and 18-23°C (Lüning, 1990; Kain & Norton, 1990).

Laminaria hyperborea is a boreal/northern species with a geographic range from mid Portugal to northern Norway (Birket et al., 1998), and a mid range within southern Norway (60°-65° North) (Kain, 1971). The average seawater temperature for southern Norway in October is 12-13°C (Miller et al., 2009), and average annual sea temperature, from 1970-2014, is 8°C (Beszczynska-Möller & Dye, 2013). The available information suggests that Laminaria hyperborea and habitat structure would not be affected, and may benefit from a water temperature decrease of 5°C over a month or 2°C for one year.

Sensitivity assessment. Resistance to the pressure is considered ‘High’, and resilience ‘High’. The sensitivity of this biotope to decreases in temperature has been assessed as ‘Not Sensitive’.

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

Lüning (1990) suggest that ‘kelps’ are stenohaline, their general tolerance to salinity as a phenotypic group covering 16 -50 psu over a 24 hr period. Optimal growth probably occurs between 30 -35 psu (MNCR category ‘Full’ salinity) and growth rates are likely to be affected by periodic salinity stress. Birkett et al. (1998) suggests that long term increases in salinity may affect Laminaria hyperborea growth and may result in loss of affected kelp, and therefore loss of the biotope.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’. The sensitivity of this biotope to an increase in salinity has been assessed as ‘Medium’.

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

Lüning (1990) suggest that ‘kelps’ are stenohaline, their general tolerance to salinity as a phenotypic group covering 16 - 50 psu over a 24 hr period. Optimal growth probably occurs between 30-35 psu (MNCR category-Full Salinity) and growth rates are likely to be affected by periodic salinity stress. Birkett et al,. (1998) suggest that long term changes in salinity may result in loss of affected kelp and, therefore loss of this biotope.

Hopkin & Kain (1978) tested Laminaria hyperborea sporophyte growth at various low salinity treatments. The results showed that Laminaria hyperborea sporophytes could grow ‘normally’ at 19 psu, growth was reduced at 16 psu and did not grow at 7 psu. A decrease in one MNCR salinity scale from Full Salinity (30-40psu) to Reduced Salinity (18-30 psu) would result in a decrease of Laminaria hyperborea sporophyte growth.

If salinity was returned to Full Salinity (30-40 psu) Laminaria hyperborea could out-compete Saccharina latissma and re-establish community dominance in 2-4 years (Kain, 1975; Leinaas & Christie, 1996), however full habitat structure may take over 10 years to recover (Birkett et al., 1998; Cristie et al., 1998). The ability of Laminaria hyperborea to out-compete Undaria pinnatifida within the UK is however unknown (Heiser et al., 2014), and as such interspecific interaction between Laminaria hyperborea and Undaria pinnatifida is not included within this sensitivity assessment.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’. The sensitivity of this biotope to decreases in salinity has been assessed as ‘Medium’.

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

Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is a growth form of Laminaria hyperborea found in extremely sheltered habitats, such as sea lochs. At a sheltered location in southern Norway, Svendsen & Kain (1971) transplanted six cape-form Laminaria hyperborea from 15 m Below Chart Datum (BCD) to 0.5 m BCD. After six months none of the cape-form Laminaria hyperborea had survived at 0.5m and only their holdfasts were still present. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Svendsen & Kain (1971) suggested increased wave action at 0.5 m was the reason why none of the cape-form Laminaria hyperborea survived beyond six months. Although the wave exposure at the site was not formally tested, this evidence suggests that cape-form Laminaria hyperborea is highly sensitive to physical disturbance e.g. from water movement (wave action and/or tidal movement).

Sensitivity assessment. IR.LIR.K.LhypCape occurs exclusively in tidal streams of <0.5 m/s. An increase in tidal streams >0.5 m may lead to significant mortality of cape-from Laminaria hyperborea and resultant loss of the characteristic species which defines this biotope.  Laminaria hyperborea can however recover within a period of 2-4 years. Resistance to the pressure is considered ‘None’, and resilience ‘Medium’. The sensitivity of this biotope to changes in peak mean spring bed velocity has been assessed as ‘Medium’.

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

The upper limit of the Laminaria hyperborea bed is determined by wave action and water flow, desiccation, and competition from the emergence resistant Laminaria digitata. Laminaria hyperborea exposed at extreme low water are very intolerant of desiccation, the most noticeable effect being bleaching of the frond and subsequent death of the meristem and loss of the plant.

Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is found from ca 4-25 m BCD (Svendsen & Kain, 1971; Connor et al., 2004). Svendsen & Kain (1971) conducted a transplantation experiment to observe if cape-form fronds (of cape-form Laminaria hyperborea) were a phenotypic response of Laminaria hyperborea to low water movement. At a sheltered location in southern Norway, six cape-form Laminaria hyperborea were transplanted from 15 m Below Chart Datum (BCD) to 0.5 m BCD and ten Laminaria hyperborea vice versa. After six months none of the cape-form Laminaria hyperborea had survived at 0.5 m and only their holdfasts were still present. Of the ten Laminaria hyperborea transplanted to 15 m BCD, four survived and produced cape-form fronds. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Svendsen & Kain (1971) suggested increased wave action at 0.5 m was the reason why none of the cape-form Laminaria hyperborea survived beyond six months. Although the wave exposure at the site was not formally tested, this evidence suggests that cape-form Laminaria hyperborea is highly sensitive to physical disturbance e.g. from water movement (wave action and/or tidal movement).

Sensitivity assessment. Increased emergence is likely to lead to high mortality of Laminaria hyperborea through desiccation. Increased wave action in shallow water (0.5 m BCD) may also cause high mortality of shallow water example of the cape-form Laminaria hyperborea biotope. Resistance to the pressure is considered ‘None’, and resilience ‘Medium’. The sensitivity of this biotope to changes in tidal emergence has been assessed as ‘Medium’.

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

Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is a growth form of Laminaria hyperborea found in extremely sheltered habitats, such as Scottish sea lochs or Irish sea loughs. Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is a growth form of Laminaria hyperborea found in extremely sheltered habitats, such as sea lochs. At a sheltered location in southern Norway, Svendsen & Kain (1971) transplanted six cape-form Laminaria hyperborea from 15 m Below Chart Datum (BCD) to 0.5 m BCD. After six months none of the cape-form Laminaria hyperborea had survived at 0.5 m and only their holdfasts were still present. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Svendsen & Kain (1971) suggested increased wave action at 0.5 m was the reason why none of the cape-form Laminaria hyperborea survived beyond six months. Although the wave exposure at the site was not formally tested, this evidence suggests that cape-form Laminaria hyperborea is highly sensitive to physical disturbance e.g. from water movement (wave action and/or tidal movement).

Svendsen & Kain (1971) suggested that the cape-form Laminaria hyperborea was highly sensitive to physical disturbance, e.g. from water movement. IR.LIR.K.LhypCape occurs exclusively within sheltered-extremely wave sheltered sites. Sheltered sites have a maximum wind fetch of 20 km, and typically experience negligible wave exposure (Connor et al., 2004). At sheltered sites, which experience higher wave exposure than extremely sheltered sites, cape-form Laminaria hyperborea can still persist but not in shallow water (<6 m, Svendsen & Kain 1971). An increase in nearshore significant wave height may therefore lead to significant mortality of cape-from Laminaria hyperborea in shallow water (0-5 m BCD) and therefore dramatically change the biotope structure of IR.LIR.K.LhypCape.

Sensitivity assessment. Resilience of IR.LIR.K.LhypCape to changes in wave height is based on Laminaria hyperborea recovery following commercial harvesting and information on life history traits (see resilience section for evidence base). Resistance to the pressure is considered ‘None’, and resilience ‘Medium’. The sensitivity of this biotope to changes in peak mean spring bed velocity has been assessed as ‘Medium’.

Chemical Pressures

 ResistanceResilienceSensitivity
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

This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

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 a,. (1999) reported that Hg was very toxic to macrophytes.  Similarly, Hopkin & Kain (1978) demonstrated sub-lethal effects of heavy metals on Laminaria hyperborea gametophytes and sporophytes, including reduced growth and respiration. Sheppard et al., (1980) noted that increasing levels of heavy metal contamination along the west coast of Britain reduced species number and richness in holdfast fauna, except for suspension feeders which became increasingly dominant. Gastropods may be relatively tolerant of heavy metal pollution (Bryan, 1984). Echinus esculentus recruitment is likely to be impaired by heavy metal contamination due to the intolerance of its larvae. Echinus esculentus are long-lived and poor recruitment may not reduce grazing pressure in the short term. Although macroalgae species may not be killed, except by high levels of contamination, reduced growth rates may impair the ability of the biotope to recover from other environmental disturbances.

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

This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

Laminaria hyperborea fronds, being almost exclusively subtidal, would not come into contact with freshly released oil, but only to sinking emulsified oil and oil adsorbed onto particles (Birket et al., 1998). The mucilaginous slime layer coating of laminarians 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 forest. Similarly, surveys of subtidal communities at a number sites between 1 -22.5 m below chart datum, including Laminaria hyperborea communities, 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 (Sommerfield & Warwick, 1999). Laboratory studies of the effects of oil and dispersants on several red algae species, including Delesseria sanguinea (Grandy 1984; cited in Holt et al., 1995) concluded that they were all sensitive to oil/ dispersant mixtures, with little differences between adults, sporelings, diploid or haploid life stages. Holt et al., (1995) concluded that Delesseria sanguinea is probably generally sensitive of chemical contamination. Overall the red algae are likely to be highly intolerant to hydrocarbon contamination. Loss of red algae is likely to reduce the species richness and diversity of the biotope and the understorey may become dominated by encrusting corallines; however, red algae are likely to recover relatively quickly.

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

This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

O'Brien & Dixon (1976) suggested that red algae were the most sensitive group of macrophytes to oil and dispersant contamination (see Smith, 1968).  Although Laminaria hyperborea sporelings and gametophytes are intolerant of atrazine (and probably other herbicides) overall they may be relatively tolerant of synthetic chemicals (Holt et al., 1995). Laminaria hyperborea survived within >55 m from the acidified halogenated effluent discharge polluting Amlwch Bay, Anglesey, albeit at low density. These specimens were greater than 5 years of age, suggesting that spores and/or early stages were more intolerant (Hoare & Hiscock, 1974). Patella pellucida was excluded from Amlwch Bay by the pollution and the species richness of the holdfast fauna decreased with proximity to the effluent discharge; amphipods were particularly intolerant although polychaetes were the least affected (Hoare & Hiscock, 1974). The richness of epifauna/flora decreased near the source of the effluent and epiphytes were absent from Laminaria hyperborea stipes within Amlwch Bay. The red alga Phyllophora membranifolia was also tolerant of the effluent in Amlwch Bay. Smith (1968) also 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. Delesseria sanguinea was probably to most intolerant since it was damaged at depths of 6m (Smith, 1968). Holt et al., (1995) suggested that Delesseria sanguinea is probably generally sensitive of chemical contamination. Although Laminaria hyperborea may be relatively insensitive to synthetic chemical pollution, evidence suggests that grazing gastropods, amphipods and red algae are sensitive. Loss of red algae is likely to reduce the species richness and diversity of the biotope and the understorey may become dominated by encrusting corallines; however, red algae are likely to recover relatively quickly.

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

Not sensitive at the pressure benchmark that assumes compliance with all relevant environmental protection standards.

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

Reduced oxygen concentrations have been shown to 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).

Sensitivity Assessment.  Reduced oxygen levels are likely to inhibit photosynthesis and respiration but not cause a loss of the macroalgae population directly. However, small invertebrate epifauna may be lost, causing a reduction in species richness. Therefore a resistance of ‘High’ is recorded. Resilience is likely to be ‘High’, and the biotopes is probably ‘Not sensitive’ at the benchmark level.

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

This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with good status as defined by the WFD.

Holt et al. (1995) suggest that Laminaria hyperborea may be tolerant of nutrient enrichment since healthy populations are found at ends of sublittoral untreated sewage outfalls in the Isle of Man. Increased nutrient levels e.g. from sewage outfalls, has been associated with increases in abundance, primary biomass and Laminaria hyperborea stipe production but with concomitant decreases in species numbers and diversity (Fletcher, 1996).

Increased nutrients may result in phytoplankton blooms that increase turbidity (see above). Increased nutrients may favour sea urchins, e.g. Echinus esculentus, due their ability to absorb dissolved organics, and result in increased grazing pressure leading to loss of understorey epiflora/fauna, decreased kelp recruitment and possibly 'urchin barrens'. Therefore, although nutrients may not affect kelps directly, indirect effects such as turbidity, siltation and competition may significantly affect the structure of the biotope.

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

Holt et al. (1995) suggest that Laminaria hyperborea may be tolerant of organic enrichment since healthy populations are found at ends of sublittoral untreated sewage outfalls in the Isle of Man. Increased nutrient levels e.g. from sewage outfalls, has been associated with increases in abundance, primary biomass and Laminaria hyperborea stipe production but with concomitant decreases in species numbers and diversity (Fletcher, 1996). Increase in ephemeral and opportunistic algae are associated with reduced numbers of perennial macrophytes (Fletcher, 1996). Increased nutrients may also result in phytoplankton blooms that increase turbidity. Therefore, although nutrients may not affect kelps directly, indirect effects such as turbidity may significantly affect the structure of Laminaria hyperborea biotopes.

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

Physical Pressures

 ResistanceResilienceSensitivity
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

If rock substrata were replaced with sedimentary substrata this would represent a fundamental change in habitat type, which Laminaria hyperborea would not be able to tolerate (Birket et al., 1998). The biotope would be lost.

Sensitivity assessment. Resistance to the pressure is considered ‘None’, and resilience ‘Very Low’ or None. The sensitivity of this biotope to change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa is assessed as ‘High’.

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 to bedrock biotopes.

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

The species characterizing this biotope are epifauna or epiflora occurring on rock and would be sensitive to the removal of the habitat. However, extraction of rock substratum is considered unlikely and this pressure is considered to be ‘Not relevant’ to hard substratum habitats.

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

Svendsen & Kain (1971) conducted a transplantation experiment to observe if cape-form fronds (of cape-form Laminaria hyperborea) were a phenotypic response of Laminaria hyperborea to low water movement. At a sheltered location in southern Norway, six cape-form Laminaria hyperborea were transplanted from 15 m below Chart Datum (BCD) to 0.5 m BCD and ten Laminaria hyperborea vice versa. After six months none of the cape-form Laminaria hyperborea had survived at 0.5 m and only their holdfasts were still present. Of the ten Laminaria hyperborea transplanted to 15 m BCD, four survived and produced cape-form fronds. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Svendsen & Kain (1971) therefore indicates that cape-form Laminaria hyperborea would be highly sensitive to abrasion.

Resilience of IR.LIR.K.LhypCape to abrasion is based on Laminaria hyperborea recovery following commercial harvesting and information on life history traits (see resilience section for evidence base).

Sensitivity assessment. The cape form of Laminaria hyperborea is particularly fragile and susceptible to physical disturbance (Svendsen & Kain, 1971). Loss of this distinctive characterizing species would result in loss of the biotope. Therefore resistance to the pressure is considered ‘None’, and resilience ‘Medium’. The sensitivity of this biotope to damage to seabed surface features is 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

Not Relevant, please refer to pressure ‘Abrasion/disturbance of the substratum on the surface of the seabed’.

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

Suspended Particle Matter (SPM) concentration has a 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 kelp depth range (Birkett et al., 1998). Light penetration influences the maximum depth at which kelp species can grow and it has been reported that laminarians grow down to 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 Laminaria hyperborea 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 (Birkett et al. 1998b; Lüning, 1990).

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 affect the photosynthetic ability of Laminaria hyperborea and Laminaria ochroleuca and decrease Laminaria hyperborea abundance and density (see sub-biotope- IR.MIR.KR.Lhyp.Pk). Kain (1964) suggested that early Laminaria hyperborea gametophyte development could occur in the absence of light. Furthermore, observations from south Norway found that a pool of Laminaria hyperborea recruits could persist growing beneath Laminaria hyperborea canopies for several years, indicating that sporophyte growth can occur in light-limited environments (Christe et al., 1998). However in habitats exposed to high levels of suspended silts Laminaria hyperborea is outcompeted by Saccharina latissima, a silt tolerant species, and thus, a decrease in water clarity is likely to decrease the abundance of Laminaria hyperborea in the affected area (Norton, 1978).

Sensitivity Assessment. Changes in water clarity are likely to affect photosynthetic rates and enable Saccharina latissima to compete more successfully with Laminaria hyperborea.  A decrease in turbidity is likely to support enhanced growth (and possible habitat expansion) and is therefore not considered in this assessment.  An increase in water clarity from clear to intermediate (10-100 mg/l) represents a change in light attenuation of ca 0.67-6.7 Kd/m, and is likely to result in a greater than 50% reduction in photosynthesis of Laminaria spp. Therefore, as this biotope occurs in the vicinty of sediments and is already silted, the dominant kelp species will probably suffer a significant decline and resistance to this pressure is assessed as ‘None’. Resilience to this pressure is probably ‘Medium’ at the benchmark.  Hence, this biotope is assessed as having a sensitivity of ‘Medium ‘to this pressure.

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

Smothering by sediment e.g. 5 cm material during a discrete event, is unlikely to directly damage cape-form Laminaria hyperborea plants but inundation of sediment is likely to provide a barrier which may inhibit zoospore settlement and affect gametophyte survival (Birkett et al., 1998). Given the microscopic size of the gametophyte, 5 cm of sediment could be expected to significantly inhibit growth. Laboratory studies showed that Laminaria hyperborea gametophytes survived 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). IR.LIR.K.LhypCape is generally typified by low water movement (low wave and tidal exposure) and often found in close proximity to silted or muddy biotopes e.g. CR.LCR.BrAs.AmenCio and SS.SMu.CSaMu.VirOphPmax (Connor et al., 2004). Deposited sediments may therefore be retained within the resident habitat for numerous tidal cycles, and could affect kelp recruitment and the survival of the understory community (Birkett et al., 1998). Laminaria hyperborea can live for greater than 10 years (Pederson et al., 2012) and is therefore likely to persist following ‘Light’ deposition of up to 5 cm of fine material added to the seabed in a single, discrete event, however Laminaria hyperborea recruitment processes may be negatively affected and the understory community be denuded until the sediment is cleared. Following clearance of deposited sediment Laminaria hyperborea populations and the understory communities are expected to recover quickly.

Sensitivity assessment. Resistance to the pressure is considered ‘High’, and resilience ‘High’. The sensitivity of this biotope to light deposition of up to 5cm of fine material added to the seabed in a single discreet event is assessed as ‘Low’.

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

Cape-form Laminaria hyperborea stipe is described as short, normally less than 50cm long (Svendsen & Kain 1971). Smothering by sediment e.g. 30 cm material during a discrete event, may inundate entire plants for extended periods and cause mortality of Laminaria hyperborea. Heavy deposition would also provide a barrier which may inhibit zoospore settlement and affect gametophyte survival (Birkett et al., 1998). Given the microscopic size of the gametophyte, 30 cm of sediment could be expected to significantly inhibit growth. Laboratory studies showed that Laminaria hyperborea gametophytes survived 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).The understory epifauna/flora may be adversely affected, e.g. suspension or filter feeding fauna and/or algal species. If clearance of deposited sediment occurs rapidly then understory communities are expected to recover quickly.

Due to the short length of cape-form Laminaria hyperborea stipes (normally <50 cm) a large number of plants may be inundated by a ‘heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Inundation is also likely to smother the understory red seaweed and faunal community plus inhibt Laminaria hyperborea photosynthesis and respiration. IR.LIR.K.LhypCape is a low energy habitat in which deposited sediments are likely to remain within the habitat for numerous tidal cycles. Once the sediment is removed however Laminaria hyperborea has been shown to recover within 2-6 years (Kain, 1975; Lienaas & Christie, 1996). The associated understory community of red seaweeds is expected to recover relatively quickly.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’. The sensitivity of this biotope to heavy deposition of up to 30 cm of fine material added to the seabed in a single discreet event is 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

No evidence. At the time of writing there is no evidence to suggest that litter would affect Laminaria hyperborea or associated habitats.

Not relevant (NR) 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

Macroalgae have no hearing perception but vibrations may cause an impact, however no studies exist to support an assessment. Sensitivity has been assessed as ‘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 Laminaria hyperborea. Shading of the biotope (e.g. by construction of a pontoon, pier etc) could adversely affect the biotope 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 laminarian abundance from forest to park type biotopes.

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

 ResistanceResilienceSensitivity
Not relevant (NR) 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 regarding the genetic modification or effects of translocation of native populations was found.

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

Undaria pinnatifida has received a large amount of research attention as a major Invasive Non Indigenous Species (INIS) which could out-compete native UK kelp habitats (see Farrell & Fletcher, 2006; Thompson & Schiel, 2012, Brodie et al., 2014; Hieser et al., 2014). Undaria pinnatifida was first recorded in the UK, Hamble Estuary, in June 1994 (Fletcher & Manfredi, 1995) and has since spread to a number of British ports. Undaria pinnatifida is an annual species, sporophytes appear in Autumn and grow rapidly throughout winter and spring during which they can reach a length of 1.65 m (Birkett et al., 1998). Farrell & Fletcher (2006) suggested that native short lived species that occupy similar ecological niches to Undaria pinnatifida, such as Saccharina latissima, Saccorhiza polyschides or Desmarestia spp., are likely to be worst affected and outcompeted by Undaria pinnatifida. Where present an abundance of Undaria pinnatifida has corresponded to a decline in Saccharina lattisima (Farrell & Fletcher, 2006) and Laminaria hyperborea (Hieser et al., 2014).

In New Zealand, Thompson & Schiel (2012) observed that native fucoids could out-compete Undaria pinnatifida and re-dominate the substratum. However, Thompson & Schiel (2012) suggested the fucoid recovery was partially due to an annual Undaria pinnatifida die back, which as noted by Heiser et al. (2014) does not occur in Plymouth sound, UK. 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 Farrell & Fletcher (1999), once established Undaria pinadifida resists most attempts of long term removal. The biotope is unlikely to fully recover until Undaria pinnatifida is fully removed from the habitat, which as stated above is unlikely to occur.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Very low’. The sensitivity of this biotope to introduction of  invasive non-indigenous species is assessed as ‘High’.

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

Galls on the blade of Laminaria hyperborea and spot disease are associated with the endophyte Streblonema sp. although the causal agent is unknown (bacteria, virus or endophyte). Resultant damage to the blade and stipe may increase losses in storms. The endophyte inhibits spore production and therefore recruitment and recoverability (Lein et al., 1991).

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

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

At the time of writing no evidence could be found on harvesting of cape-form Laminaria hyperborea. As noted by Sjøtun et al. (1998) cape form Laminaria hyperborea plants, on average, have a lower biomass than Laminaria hyperborea from exposed habitats (e.g. IR.HIR.Kfra.LhypR), and is therefore unlikely to be of the same commercial value. Svendsen & Kain (1971) conducted a transplantation experiment to observe if cape-form fronds (of cape-form Laminaria hyperborea) were a phenotypic response of Laminaria hyperborea to low water movement. At a sheltered location in southern Norway, six cape-form Laminaria hyperborea were transplanted from 15 m below Chart Datum (BCD) to 0.5 m BCD and ten Laminaria hyperborea vice versa.  After six months none of the cape-form Laminaria hyperborea had survived at 0.5 m and only their holdfasts were still present. Of the ten Laminaria hyperborea transplanted to 15 m BCD, four survived and produced cape-form fronds. Svendsen & Kain (1971) noted whilst transporting the six cape-form Laminaria hyperborea, the cape-form fronds were very fragile and often ruptured under their own weight. Cape-form Laminaria hyperborea is therefore thought to be extremely fragile and brittle, physical disturbance of any nature is likely to result in mortality.

A number of review and experimental publications have assessed the recovery of Laminaria hyperborea beds and the associated community within high energy habitats. If environmental conditions are favourable Laminaria hyperborea can recover following disturbance events reaching comparable plant densities and size to pristine Laminaria hyperborea beds within 2-6 years (Kain, 1979; Birkett et al., 1998; Christie et al., 1998). Holdfast communities may recover in 6 years (Birkett et al., 1998). Full epiphytic community and stipe habitat complexity regeneration requires over 6 years to recover (possibly 10 years). These recovery rates were based on observations of discrete kelp harvesting events, recurrent disturbance occurring frequently within 2-6 years of the initial disturbance is likely to lengthen recovery time (Birkett et al., 1998; Burrows et al., 2014). Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonisers and succession community differed between blocks and at what time of year the blocks were cleared however within 2 years of clearance the blocks were dominated by Laminaria hyperborea. Lienaas & Christie (1996) also observed Laminaria hyperborea re-colonisation of ‘urchin barrens’, following removal of urchins. The substratum was initially colonized by filamentous macroalgae and Saccharina latissima however after 2-4 years Laminaria hyperborea dominated the community.

Sensitivity assessment. Targeted removal of kelp from this biotope is likely to result in loss of the biotope. Resistance to the pressure is considered ‘None’. However, the resilience is assessed as ‘Medium’ and the sensitivity of this biotope is considered to be ‘Medium’.

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

At the time of writing no evidence could be found on harvesting (incidental or intentional trawling) of cape-form Laminaria hyperborea. As noted by Sjøtun et al., (1998) cape form Laminaria hyperborea plants, on average, have a lower biomass than Laminaria hyperborea from exposed habitats (e.g. IR.HIR.Kfra.LhypR), and is therefore unlikely to be of the same value. Laminaria hyperborea cape form is highly sensitive to any physical disturbance. Incidental/accidental removal of cape-form Laminaria hyperborea as a result of other fisheries e.g. Pectin maximus collection within SS.SMu.CSaMu.VirOphPmax which is often in close proximity to IR.LIR.K.LhypCape (Connor et al., 2004),  is likely to cause similar effects to that of direct harvesting; as such the same evidence has been used for both pressure assessments.

Cape-form Laminaria hyperborea (Laminaria hyperborea f. cucullata) is a growth form of Laminaria hyperborea found in extremely sheltered habitats, such as Scottish sea lochs or Irish Sea Loughs. Svendsen & Kain (1971) conducted a transplant experiment between Laminaria hyperborea and cape-form Laminaria hyperborea. 100% mortality of cape-form Laminaria hyperborea was suggested to be a result of increased wave exposure at the transplanted site. Furthermore in transit to the host site, cape-form Laminaria hyperborea was noted to be extremely brittle and fronds often ruptured under their own weight. Cape-form Laminaria hyperborea is therefore thought to be extremely fragile and brittle, physical disturbance of any nature is likely to result in mortality.

A number of review and experimental publications have assessed the recovery of Laminaria hyperborea beds and the associated community within high energy habitats. If environmental conditions are favourable Laminaria hyperborea can recover following disturbance events reaching comparable plant densities and size to pristine Laminaria hyperborea beds within 2-6 years (Kain, 1979; Birkett et al., 1998; Christie et al., 1998). Holdfast communities may recover in 6 years (Birkett et al., 1998). Full epiphytic community and stipe habitat complexity regeneration requires over 6 years to recover (possibly 10 years). These recovery rates were based on observations of discrete kelp harvesting events, recurrent disturbance occurring frequently within 2-6 years of the initial disturbance is likely to lengthen recovery time (Birkett et al., 1998; Burrows et al., 2014). Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonisers and succession community differed between blocks and at what time of year the blocks were cleared however within 2 years of clearance the blocks were dominated by Laminaria hyperborea. Lienaas & Christie (1996) also observed Laminaria hyperborea re-colonisation of ‘urchin barrens’, following removal of urchins. The substratum was initially colinized by filamentous macroalgae and Saccharina latissima however after 2-4 years Laminaria hyperborea dominated the community.

Sensitivity assessment. Resistance to the pressure is considered ‘None’, and resilience ‘Medium’. Sensitivityhas been assessed as ‘Medium’.

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Citation

This review can be cited as:

Stamp, T.E., 2015. Silted cape-form [Laminaria hyperborea] on very sheltered infralittoral rock. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/habitat/detail/1030

Last Updated: 25/09/2015

Tags: cape kelp