Biodiversity & Conservation

IR.EIR.KFaR.LhypFa

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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The community is mainly of attached species that would be removed with the substratum. Therefore intolerance is high. Overall, it is expected that qualitative recovery will occur within two or three years but growth of kelp plants and development of their associated biota will take longer and so a recoverability of moderate is suggested. (See additional information below.)
Smothering
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The strongly wave exposed habitat that this biotope occurs in suggests that smothering by deposition of sediment is unlikely and is more likely to be due to overgrowth by other organisms. However, many of the conspicuous and characterizing species will protrude above smothering and survive. Intolerance is therefore intermediate. The main slow growing and long-lived species will be present after smothering is removed and most characterizing species will re-colonize within a couple of years so that recoverability is high.
Increase in suspended sediment
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Whilst the biotope occurs in open coast areas where levels of suspended sediment are generally low, increase in levels of silt is expected to have only a minor impact perhaps by increasing the energy required to clean silt from the feeding structures of organisms. On return to normal conditions of suspended sediment, recovery is likely to be very rapid. (The effects of increased suspended sediment on turbidity are assessed below.)
Decrease in suspended sediment
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The biotope occurs in open coast areas where levels of suspended sediment are generally low. Although suspended sediment may include some nutrients, the suspension feeding animals rely largely on planktonic organisms and it is not felt there would be any disbenefit. Indeed, less suspended sediment may lead to a reduced requirement for expenditure of energy on cleaning.
Desiccation
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This biotope is subtidal and will not be exposed to desiccation.
Increase in emergence regime
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This biotope occurs in the shallow infralittoral and so an increase in emergence may adversely affect species in the biotope. The key structuring species Laminaria hyperborea is primarily a subtidal species and is likely to be highly intolerant of increases in emergence. Its upper limit on the shore is in part dependant on the emergence regime as well as competition from more desiccation tolerant species such as Laminaria digitata. Other species such as Delesseria sanguinea, Botryllus schlosseri and Alcyonium digitatum do occur on the lower shore and so some desiccation tolerance is likely. The part of the biotope that is subject to emergence will have a high intolerance and mortalities will occur. However, many of the component species will survive and, once kelp plants are re-established, the biotope will be reinstated. A recoverability of high is recorded.
Decrease in emergence regime
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This biotope is subtidal and so decreased emergence is not relevant.
Increase in water flow rate
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The biotope is characteristic of very wave exposed conditions where water movement from wave action will greatly exceed the strength of any possible tidal flow. The biotope is therefore considered to be not sensitive.
Decrease in water flow rate
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The biotope is characteristic of very wave exposed conditions so that any decrease in tidal flow will be nullified by the wave action effects. The biotope is therefore considered to be not sensitive.
Increase in temperature
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Most of the species in the biotope have a distribution that extends well to the south of the British Isles suggesting that increase in temperature will not affect the types of species dominating the biotope. There is little evidence for effects of short-term increase in temperature on component species although Delesseria sanguinea is recorded as tolerant of 23 °C for a week (Lüning, 1984) but dies rapidly at 25°C . In the case of the sea urchin Echinus esculentus, Bishop (1985) suggested that this species cannot tolerate high temperatures for prolonged periods due to increased respiration rate and resultant metabolic stress. Therefore, Echinus esculentus is likely to exhibit a 'low' intolerance to chronic long term temperature change but would probably be more intolerant of sudden or short term acute change (e.g. 5 C for 3 days) in temperature. The northern sea weed Odonthalia dentata is often abundant in the biotope and will most likely become less abundant in relation to long-term, but not short-term change. A similar situation exists for Alaria esculenta. Other species such as the jewel anemone Corynactis viridis (which reaches its northern limit of distribution in Scotland) may be favoured by an increase in temperature. Overall, low intolerance is suggested.
Decrease in temperature
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Most of the species in the biotope have a distribution that extends well to the north of the British Isles suggesting that decrease in temperature will not affect the types of species dominating the biotope. The northern sea weed Odonthalia dentata is often abundant in the biotope and will most likely become more abundant in relation to long-term, but not short-term change. A similar situation exists for Alaria esculenta. Other species such as the jewel anemone Corynactis viridis (which reaches its northern limit of distribution in Scotland) may be adversely affected by an decrease in temperature. There is little other evidence except that Urticina felina was apparently unaffected by the extremely cold winter of 1962/3 (Crisp, 1964). Overall, low intolerance is suggested.
Increase in turbidity
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The biotope occurs in the upper photic zone and so increased turbidity would not be expected to cause significant adverse effects on photosynthesis and survival of seaweeds. For species such as Delesseria sanguinea that grow rapidly in spring, some reduction in growth rate as a result of lower light at that time may occur. Animal species would probably be unaffected. The overwhelming reason for the occurrence of this biotope is strong wave action in shallow depths and increased turbidity would not be expected to have any significant effect. However, because there may be some adverse effect on growth in algae, an intolerance of low is suggested.
Decrease in turbidity
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The most significant effect of decreased turbidity is increased light penetration. The biotope occurs in the upper photic zone and so light penetration is already high. For species such as Delesseria sanguinea that grow rapidly in spring, some increase in growth rate as a result of higher light at that time may occur. Animal species would be expected to be unaffected. The overwhelming reason for the occurrence of this biotope is strong wave action in shallow depths and decreased turbidity would not be expected to have any significant effect. Because any effect is likely to be to encourage algal growth, intolerance is suggested as not sensitive*.
Increase in wave exposure
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This biotope already occurs on some of the most wave exposed coasts in Britain. Any increase in wave action might result in the replacement of Laminaria hyperborea with Alaria esculenta and possibly Laminaria digitata. Sea urchins may be displaced by extremely strong wave action. Animals, especially hydroids Tubularia indivisa, the jewel anemone Corynactis viridis and encrusting sponges may dominate over seaweeds. The biotope is, after long-term increased exposure, likely to become similar to EIR.AlaAnSC (Alaria esculenta forest with dense anemones and sponge crusts on extremely exposed infralittoral bedrock). Therefore, as the biotope is likely to be changed to a different biotope, intolerance is assessed as high. Different species would dominate and species richness would fall. Reversion to EIR.LhypFa would occur within a few years as most elements of the biotope have planktonic propagules.
Decrease in wave exposure
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The overwhelming reason for the occurrence of this biotope is strong wave action in shallow depths. A decrease in wave exposure would most likely lead to the development of a different biotope such as EIR.LhypR.Ft (Laminaria hyperborea forest with dense foliose red seaweeds on exposed upper infralittoral rock). The cushion fauna in EIR.LhypR.Ft is markedly less abundant than kelp forests in EIR.LhypFa and, whilst sponges, anemones and polyclinid ascidians may be present, they do not occur at high abundance. Therefore, as the biotope is likely to be changed to a different biotope, intolerance is assessed as high. Different species would dominate but species richness would most likely rise. Reversion to EIR.LhypFa would occur within a few years as most elements of the biotope have planktonic propagules.
Noise
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Species in this biotope are algae and sessile invertebrates not known to be sensitive to noise.
Visual Presence
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Species in this biotope are algae and sessile invertebrates not known to be sensitive to visual presence.
Abrasion & physical disturbance
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Although tough enough to withstand strong wave action, species in this biotope are likely to be detached by abrasive force. For example, a passing scallop dredge would have an effect similar to a kelp harvesting, although more localized and on a smaller scale (see below). Therefore an intolerance of intermediate has been recorded. Whilst recovery may occur for some species from parts remaining in crevices, others such as Laminaria hyperborea will have to recover from sporelings already present or that settle after the event. For recoverability, see additional information below.
Displacement
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The dominant species in the biotope are sessile and therefore will not survive if displaced. The effect on the biotope is therefore likely to be similar to abrasion where an intolerance of high and recoverability of high are assessed.

Chemical Factors

Synthetic compound contamination
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Several of the characterizing species, particularly red algae, in this biotope appear to be intolerant of synthetic chemicals. Much information comes from the study of dispersant used during oil spills or in experimental studies. O'Brien & Dixon (1976) suggested that red algae were the most sensitive group of algae to oil or dispersant contamination, possibly due to the susceptibility of phycoerythrins to destruction, and that the filamentous forms were the most sensitive. Heavy mortality of Delesseria sanguinea occurred down to 12 m after the 'Torrey Canyon' oil spill (probably due to a mixture of wave action and dispersant application). 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. Smith (1968) reported dead colonies of Alcyonium digitatum at a depth of 16m in the locality of Sennen Cove (Pedu-men-du, Cornwall) resulting from the offshore spread and toxic effect of detergents (a mixture of a surfactant and an organic solvent) e.g. BP 1002 sprayed along the shoreline to disperse oil from the 'Torrey Canyon' tanker spill. Cole et al. (1999) suggested that herbicides , such as simazina and atrazine were very toxic to macrophytes. Hoare & Hiscock (1974) noted that Delesseria sanguinea was excluded from Amlwch Bay, Anglesey by acidified halogenated effluent discharge although plants of Laminaria hyperborea survived. Overall, it is not expected that all individuals of a species will be killed but the overall quality and species abundance are likely to be significantly reduced. Therefore, an intolerance of high has been recorded. As the dominant species in the biotope have planktonic propagules, recovery will be within two to three years.
Heavy metal contamination
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There is little evidence available for the majority of species in the biotope. 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 sub-lethal effects of Hg (organic and inorganic) on Plumaria elegans sporeling were reported by Boney (1971), for example 100 % growth inhibition was caused by 1 ppm Hg in his study. Hopkin & Kain (1978) examined the effect of Cu, Zn, Hg and Cd on Laminaria hyperborea gametophytes and sporophytes. Sublethal effects on sporophyte development, growth and respiration were shown for Hg, Zn and Cd. Hg was found to be lethal at 0.05mg/l. However, Cu affected sporophyte development at 0.01mg/l but was lethal at 0.1 mg/l. Effects on adult plants are unlikely to be so severe as on juvenile stages. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 g / 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 Gomez & Miguez-Rodriguez (1999) above it is likely that Echinus esculentus is intolerant of heavy metal contamination (see review for Echinus esculentus). However, in a wave exposed algal dominated biotope, it is expected that sea urchin grazing has a minor role. Overall, there might be some sublethal effects on species in the biotope but, at the benchmark level, intolerance is expected to be low. Recoverability will be very high.
Hydrocarbon contamination
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Observations of the impact specifically of hydrocarbons on species in this biotope are confused by the use of dispersants in field observations. Species in the biotope are unlikely to become smothered by oil due to its subtidal position. However, O'Brien & Dixon (1976) suggested that red algae were the most sensitive group to oil or dispersant contamination, possibly due to the susceptibility of phycoerythrins to destruction, and that the filamentous forms were the most sensitive. Heavy mortality of Delesseria sanguinea occurred down to 12 m after the 'Torrey Canyon' oil spill, although it was unclear how much of the effect was due to oil rather than dispersant contamination. Holt et al. (1995) report that oil spills in the USA and the 'Torrey Canyon' spillage had little effect on kelp forest. However, sensitive species such as amphipods may be adversely affected. Rostron & Bunker (1997) could find no apparent effects on shallow sublittoral rock communities following the Sea Empress oil spill in west Wales. The biotope is expected to remain intact and intolerance is indicated as low with recoverability as very high.
Radionuclide contamination
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No information has been found for species in the biotope.
Changes in nutrient levels
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In general, the algal components of this biotope are likely to benefit from an increase in nutrients. For instance, an increase in abundance of red algae, including Delesseria sanguinea, was associated with eutrophication in the Skagerrak area, Sweden, especially in areas with the most wave exposure or water exchange (Johansson et al., 1998). However, where eutrophication resulted in high siltation rates, the delicate foliose red algae such as Delesseria sanguinea were replaced by tougher, erect red algae (Johansson et al., 1998). High nutrient levels and eutrophication may result in increased siltation and turbidity (see above). Other species in the biotope may benefit from increased organic material being available for consumption. At the benchmark level, it is considered unlikely that change will occur.
Increase in salinity
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The biotope occurs in full salinity conditions and on the open coast so that increase in salinity is not relevant.
Decrease in salinity
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The biotope occurs in full salinity and several species in the biotope do not extend into low salinity conditions including many of the red algae. However, Rietema (1993) found that North Sea specimens of Delesseria sanguinea died at 7.5 - 11 psu suggesting significant tolerance of some red algal species. Kain (1979) stated that Laminaria hyperborea grows optimally between 20 -35 psu but did not survive at 6 psu. Of the animal species in the biotope, Urticina felina and Halichondria panicea both survive in variable salinity conditions. The biotope is likely to be maintained even after reduction in salinity although some species will be lost so that intolerance is intermediate. Overall, it is expected that qualitative recovery will occur within two or three years and since decrease in salinity at the benchmark level will not affect the whole biotope, a recoverability of high is suggested.
Changes in oxygenation
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The biotope occurs in situations where water is moving constantly and oxygenation is high. A study of the effects of anaerobiosis (no oxygen) on some marine algae concluded that Delesseria sanguinea was very intolerant of anaerobic conditions and, at 15 °C, death occurs within 24hrs (Hammer, 1972). Cole et al. (1999) suggested possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. Bearing in mind the fully oxygenated conditions that this biotope normally occurs in, it is likely that species in the biotope would be highly intolerant of a period of hypoxia. For Recoverability, see Additional Information.

Biological Factors

Introduction of microbial pathogens/parasites
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Little evidence was found of effects of microbial pathogens on algae or animals in the biotope. Galls on the blade of Laminaria hyperborea and spot disease are associated with the endophyte Streblonema sp. Alcyonium digitatum acts as the host for the endoparasitic species Enalcyonium forbesi and Enalcyonium rubicundum (Stock, 1988). Parasitisation may reduce the viability of a colony but not to the extent of killing them but no further evidence was found to substantiate this suggestion. Overall, it is concluded that pathogens may reduce productivity but the biotope will be otherwise unaffected.
Introduction of non-native species
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It is possible that this biotope occurs in shallow wave exposed conditions in the Isles of Scilly where the Pacific red alga Pikea californica may dominate rocks to the exclusion of native species. However, no other non-native species that currently are known to occur in Britain and Ireland are recorded from this biotope. Therefore an intolerance of not relevant has been indicated.
Extraction
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Kelp plants Laminaria hyperborea may be extracted from this biotope and intolerance has been assessed as intermediate. The edible urchin may also be removed and this may, to a certain extent, mitigate the effects of the removal of kelp plants. However, Nichols (1981) pointed out that most divers missed small specimens within kelp beds. Research on harvested populations of Laminaria hyperborea in Norway suggests that kelp forest biomass returned to pre-harvesting levels after 1-2 years, but that the plants were mainly small (1m) and that the age structure of the population was shifted towards younger plants. Sivertsen (1991; cited in Birkett et al. 1998) showed that kelp populations stabilize after about 4-5 year post-harvesting. Re-growth was due primarily to growth of viable juveniles after harvesting. Recent advice in Norway suggest that kelp forest should be left for 7-10 years after harvesting for the kelp biomass and non-kelp species to recover (Birkett et al. 1998). Removal of mature kelp plants would remove the habitat for a wide range of associated species. However, as most species including young Laminaria hyperborea would be left by kelp harvesting, it is expected that qualitative recovery at least would occur within two to three years.

Additional information icon Additional information

Recoverability
Experimental clearance experiments (Kain 1979) in the Isle of Man showed that Laminaria hyperborea returned to near control levels of biomass within 3 years at 0.8m but that recovery was slower at 4.4m. However, Kain (1979) noted that grazing would slow recovery since, even though they did not prevent spore settlement, few sporophytes survived after 1 year in the presence of Echinus esculentus. These experiments did not remove the gametophyte 'seed' bank. Research on harvested populations of Laminaria hyperborea in Norway suggests that kelp forest biomass returned to pre-harvesting levels after 1-2 years, but that the plants were mainly small (1m) and that the age structure of the population was shifted towards younger plants. Sivertsen (1991 cited in Birkett et al. 1998) showed that kelp populations stabilize after about 4-5 year post-harvesting. However, re-growth was due primarily to growth of viable juveniles after harvesting. Other species characteristic of the biotope will also recover quickly. For instance, Kain (1975) examined recolonization of cleared concrete blocks in a subtidal kelp forest. Red algae colonized blocks within 26 weeks in the shallow subtidal (0.8m) and 33 weeks at 4.4m. Delesseria sanguinea was noted within 41 weeks (8 months) at 4.4m in one group of blocks and within 56-59 days after block clearance in another group of blocks. Sponge species, Alcyonium digitatum and ascidians are all known to colonize bare surfaces rapidly. However, advice in Norway suggests that kelp forest should be left for 7-10 years after harvesting for the kelp biomass and non-kelp species to recover (Birkett et al. 1998). Thus, full recovery after significant damage to the biotope is likely to rake in excess of five years and recoverability ranked as 'moderate'.

This review can be cited as follows:

Hiscock, K. 2001. Laminaria hyperborea forest with a faunal cushion (sponges and polyclinids) and foliose red seaweeds on very exposed upper infralittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 02/09/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=44&code=1997>