Biodiversity & Conservation

IR.EIR.KFaR.LhypR

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Key and characteristic species are highly intolerant of substratum loss. Removal of the bedrock or boulders will remove the kelp species and their gametophytes and cause more damage than harvesting alone. Intolerance has been assessed as high with a moderate recovery (see additional information).
Smothering
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Smothering by sediment e.g. 5 cm material for a month, is unlikely to damage Laminaria hyperborea plants but is likely to affect sporeling and gametophyte survival as well as holdfast fauna. A layer of sediment will interfere will zoospore settlement. Given the microscopic size of the gametophyte, 5 cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that gametophytes can survive in darkness for between 6 - 16 months at 8 °C and would probably survive smothering for 1 month. Once returned to normal conditions the gametophytes resumed growth or maturation within 1 month (very high recoverability) (tom Dieck, 1993). Intolerance to this factor is likely to be higher during the peak periods of sporulation or germling settlement. Understorey epifauna/flora may be adversely affected, especially suspension or filter feeding species and the settlement of larvae or spores may be impaired. Laminaria hyperborea, Delesseria sanguinea and Echinus esculentus were all assessed as of intermediate intolerance to smothering and accordingly, EIR.LhypR is assessed as of intermediate intolerance. Recoverability is likely to be high (see additional information).
Increase in suspended sediment
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Increased siltation may interfere with spore attachment, larval settlement and recruitment, smothering germlings and gametophytes (see above). Siltation may also reduce photosynthetic activity if deposited on lamina, and increase sediment scour of surfaces settled by algal spores or larvae (Fletcher, 1996). Fletcher (1996) reports that siltation in the vicinity of outfalls restricted the distribution of Laminaria spp. and resulted in the general absence or impoverishment of algae, leaving only a few selected species. It also increased the quantity of mussels which competed for space with benthic algae in the heavily polluted sites. Studies of cooling water discharge in a southern California Macrocystis forest suggested that turbidity and siltation significantly reduced the density of snails, sea urchins and starfish whereas two filter feeding species, a gorgonian coral and a sponge, increased in relative density (Birkett et al., 1998b). Exposed Laminaria hyperborea biotopes are likely to be free of silt and exhibit more foliose red algae than moderately exposed Laminaria hyperborea biotopes. Increased siltation may adversely affect recruitment in Helcion pellucidum and other grazing gastropods, and could result in decreases in population density resulting in increased abundance of epiphytes on stipes. Given the effect on settlement and recruitment, increased siltation may change the age structure of the algal population, reduce understorey flora/fauna species richness, and decrease gastropod grazing. Increased siltation may affect holdfast fauna, encouraging suspension feeders and silt tolerant communities (Moore, 1973a&b; Edwards, 1980). Sheppard et al. (1980) noted that increased suspended sediment (measured as clarity) reduced holdfast species diversity due to increased dominance of suspension feeders.
On balance, an intolerance of intermediate has been suggested, with very high recovery.
Decrease in suspended sediment
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EIR.Lhyp.R is likely to be tolerant of a decrease in suspended sediment and it may exhibit a more diverse foliose red algae.
Desiccation
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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. Increased desiccation will probably remove more adult plants and their associated communities and red algae from the upper limit of its distribution. Most species associated with this biotope are intolerant of increased emergence and would be adversely affected. Although the majority of the kelp bed is subtidal and unlikely to be affected, EIR.LhypR has been assessed as being highly intolerant to desiccation to reflect the likely impact at the upper shore extent of this biotope. Recovery is expected to be moderate (see additional information).
Increase in emergence regime
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An increase in emergence of about 1 hour for a year will decrease the upper limit of the kelp beds, due to the increased insolation and risk of desiccation, with a concomitant decrease in species richness. The upper shore extent of the biotope may be replaced by sublittoral fringe biotopes, such as EIR.Ala and accordingly, intolerance has been assessed as high. Recovery is expected to be moderate (see additional information). The kelp park biotope (EIR.LhypR.Pk) is unlikely to be exposed to this factor due to its depth.
Decrease in emergence regime
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A decrease in emergence may allow the kelp bed to extend its distribution further up the shore and tolerant* has been suggested.
Increase in water flow rate
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The morphology of the stipe and blade of kelps vary with water flow rate. Strong currents may lead to removal of kelps through detachment of holdfasts. Increased water flow rate may also remove or inhibit grazers including Helcion pellucidum and Echinus esculentus, therefore reducing grazing in the understorey and on stipes. The associated algal flora and suspension feeding faunal populations change significantly with different water flow regimes. Increased water flow rates may reduce the understorey epiflora, to be replaced by an epifauna dominated community (e.g. sponges, anemones and polclinid ascidians) as in the biotope EIR.LhypFa. The composition of the holdfast fauna may also change, e.g. energetic or sheltered water movements favour different species of amphipods (Moore, 1985). The recognisable biotope is likely to change significantly and, therefore, intolerance has been assessed as high with a moderate recovery (see additional information).
Decrease in water flow rate
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The morphology of the stipe and blade of kelps vary with water flow rate and the associated algal flora and suspension feeding faunal populations can also change significantly with different water flow regimes. However, EIR.LhypR is found in wave exposed and very wave exposed habitats and, therefore, wave energy is likely to far outweigh any reduction in water flow rate. The biotope may become more characteristic of moderately exposed habitats however overall, intolerance is likely to be low.
Increase in temperature
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The keystone species Laminaria hyperborea is stenothermal, with upper and lower lethal temperatures between 1-2 °C above or below the normal temperature tolerances of between 0 and 20 °C (depending on season) (Birkett et al., 1998b). Hoek (1982) suggests that Laminaria hyperborea can tolerate an annual temperature span of 17 °C with an upper and lower lethal temperatures of 19 °C and 2 °C. However, above 17 °C, gamete survival is reduced (Kain, 1971) and gametogenesis is inhibited at 21 °C in this species (tom Dieck, 1992). It is likely that the biotope as a whole will be damaged by temperatures outside the temperature tolerance of Laminaria hyperborea. Subtidal red algae are less tolerant of temperature extremes than intertidal Rhodophyceae, surviving between -2 °C (in seawater) and 18-23 °C (Lüning, 1990; Kain & Norton, 1990). Temperature increase may affect growth, recruitment or interfere with the reproductive cycle in some species. For example, there is some evidence to suggest that blade growth in Delesseria sanguinea is delayed until ambient sea temperatures fall below 13 °C, although blade growth is likely to be intrinsically linked to gametangia development (see Kain, 1987). Increases in temperature of e.g. 2 °C for a year or 5 °C for one week may raise ambient temperatures outside the tolerable range for the species within the biotope, causing changes in recruitment, growth rates and perhaps loss of red algae and changes in grazing patterns. It should be noted that increases in temperature tolerances by kelp species is less well tolerated in winter months than summer months (Birkett et al., 1998b).

Overall, EIR.LhypR has been assessed as being of high intolerance to increases in temperature at the benchmark level. Recovery is likely to be moderate (see additional information).

The sub-biotope EIR.LhypR.Loch is characterized by the presence of Laminaria ochroleuca, which is restricted to Devon, Cornwall and the Isles of Scilly but common on the coasts of Brittany. Long term increases of 1 -3 °C in temperature may allow Laminaria ochroleuca to spread northwards (Birkett et al., 1998b).
Decrease in temperature
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The keystone species Laminaria hyperborea is stenothermal, with upper and lower lethal temperatures between 1-2 °C above or below the normal temperature tolerances of between 0 and 20 °C (depending on season) (Birkett et al., 1998b). Hoek (1982) suggests that Laminaria hyperborea can tolerate an annual temperature span of 17 °C with an upper and lower lethal temperatures of 19 °C and 2 °C. Given its distribution in the North Atlantic this species is likely to be tolerant of low temperatures. The temperature tolerances of the gametophyte stages are different to those of the adult. Gametophytic development has been observed at 0 °C although development is slow and suggests that 0 °C is close to the lowest temperature allowing vegetative development of the primary cells (Sjøtun & Schoschina, 2002). Subtidal red algae are less tolerant of temperature extremes than intertidal Rhodophyceae, surviving between -2 °C (in seawater) and 18-23 °C (Lüning, 1990; Kain & Norton, 1990). However, Delesseria sanguinea is a Northern species, likely to be tolerant of a decrease in temperature. Helcion pellucidum is also a Northern species, extending as far north as the northern Norway. Overseas, cold temperatures have been associated with high recruitment of sea urchins (Birkett et al., 1998b). Although the key structural, functional and characterizing species may be relatively tolerant of a decrease in temperature at the benchmark level, an intolerance of low has been suggested to reflect the likelihood that other may species commonly found in the biotope may be intolerant, in addition to the fact that the biotope is likely to be more intolerant to an acute drop in temperature than chronic change.
Increase in turbidity
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Turbidity will primarily affect Laminaria hyperborea and affect the depth to which it is likely to grow. In the sub-biotope EIR.LhypR.Pk Laminaria hyperborea occurs at low density, due mainly to limiting light levels. Increased turbidity is likely to reduce the depth to which the kelp park extends, raising its upper limit and thereby decreasing the lower limit of the kelp forest. Red algae are shade tolerant extending to greater depths and probably not as intolerant of increases in turbidity as kelp species. Suspended material in the vicinity of outfalls has been reported to result in reduced depth range and fewer new plants under the canopy (Fletcher 1996) (see 'siltation' above). Intolerance has been assessed as intermediate. Recovery is likely to be moderate.
Decrease in turbidity
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A decrease in turbidity is likely to benefit the algal component of this biotope which may experience enhance primary productivity. Tolerant* has been suggested.
Increase in wave exposure
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Increased wave exposure is likely to remove older kelp plants, especially from the upper extent of the kelp forest, where Laminaria hyperborea may become replaced by kelps more tolerant of stronger wave action such as Laminaria digitata and Alaria esculenta. The extent of the biotope may be reduced and, therefore, intolerance has been assessed as intermediate.
Decrease in wave exposure
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Decreased wave exposure may not damage the Laminaria hyperborea forest or park, but may result in loss of foliose red algae and an increase in abundance of filamentous red algae, characteristic of the biotope MIR.Lhyp in which case the biotope will no longer be EIR.LhypR. In very wave sheltered situations Laminaria hyperborea is replaced by Saccharina latissima and the biotope may change significantly should the wave exposure drop from sheltered to very sheltered. Intolerance has been assessed as high with a moderate recovery (see additional information).
Noise
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Fish species using the kelp beds as a nursery or feeding ground may be disturbed by underwater noise or vibration. However, little information on the effect of this factor on these species was available.
Visual Presence
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Fish species using the kelp beds as a nursery or feeding ground may be affected or disturbed by visual presence but little information was found.
Abrasion & physical disturbance
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Laminarians and red algae are likely to be damaged abrasion due to anchor impact and sand or cobble scour. However, a passing scallop dredge is likely to remove or damage a proportion of the kelp and red algae present. Therefore, the community as a whole is likely to be of intermediate intolerance to physical disturbance at the benchmark level. . This biotope will be more intolerant of higher levels or frequency of physical disturbance e.g. routine or numerous anchorages. For recoverability, see additional information below.
Displacement
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Laminaria hyperborea and most other algae cannot reattach once removed and will be lost. Cleared areas were colonized by opportunistic species such as Alaria esculenta, Saccorhiza polyschides, and Desmarestia spp., but were out-competed by Laminaria hyperborea within 3 years (Kain, 1975; Kain, 1979). Norwegian studies suggest that kelp communities take at least 10 years to recover from harvesting (Svendsen, 1972, cited in Birkett et al., 1998b). Similarly many species of epifauna have a permanent attachment and would be lost if displaced. However, species such as Echinus esculentus and Helcion pellucidum are relatively insensitive to displacement.

Chemical Factors

Synthetic compound contamination
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Echinus esculentus was assessed as highly intolerant of synthetic chemicals. O'Brian & Dixon (1976) suggested that red algae were the most sensitive group of macrophytes to oil and dispersant contamination (see also 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 >55m from the acidified halogenated effluent discharge polluting Amlwch Bay, Anglesey, albeit at low density. These specimens were greater the 5 years of age, suggesting that spores and/or early stages were more intolerant (Hoare & Hiscock, 1974). Helcion pellucidum 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 Spermothamnium repens and some tufts of Jania rubens survived together with Laurencia 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 loss of red algae would result in loss of characteristic species and the biotope would cease to be EIR.LhypR. Grazing gastropods and amphipods are likely to be intolerant of synthetic chemicals such as TBT and dispersants. This biotope is primarily subtidal and unlikely to be smothered by oil but its exposure to wave action may allow dispersant chemicals to penetrate deeper into the water column, as suggested by Smith (1968). However, surveys of subtidal communities at a number sites between 1- 22.5m below chart datum, including Laminaria hyperborea communities, showed no noticeable impacts of the Sea Empress oil spill and clean up (Rostron & Bunker, 1997). Therefore, although the kelp species themselves may be relatively unaffected by synthetic contaminants, characterizing red algae and Echinus esculentus, together with grazing gastropods may be highly intolerant, resulting in significant changes in species richness and community structure. However, red algae and urchins are likely to recover relatively quickly.
Heavy metal contamination
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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. Similarly, Hopkin & Kain (1978) demonstrated sublethal affects of heavy metals of 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. Adult Echinus esculentus are long-lived and poor recruitment may not reduce grazing pressure in the short term. Although macrophyte 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.
Hydrocarbon contamination
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The mucilaginous slime layer coating 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 -22.5m 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). 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) (Gomez & Miguez-Rodriguez, 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 and sea urchins 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. During recovery the community may appear similar to grazed kelp forest biotope MIR.LhypGz.
Radionuclide contamination
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Insufficient information
Changes in nutrient levels
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Holt et al. (1995) suggest that Laminaria hyperborea may be tolerant of eutrophication since healthy populations are found at ends of sublittoral untreated sewage outfalls in the Isle of Man. Nutrients may be added to macrophyte cultures to increase productivity. 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 (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.
Increase in salinity
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The full salinity, infralittoral habitat within which this biotope occurs is unlikely to experience significant increases in salinity and this factor is considered to be irrelevant.
Decrease in salinity
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Lüning (1990) suggest that kelps are stenohaline, their tolerance to salinity covering 16 - 50 psu over a 24 hr period. Optimal growth probably occurs between 30 -35 psu and growth rates are likely to be affected by periodic salinity stress. Hopkin & Kain (1978) stated that Laminaria hyperborea early sporophytes grew optimally between 20 -35 psu but did not survive at 6 psu. The representative species suggested for this biotope are assessed as intermediate intolerance to reduced salinity. Birkett et al. (1998) suggest that long term changes in salinity may result in loss of affected kelp beds and, therefore, loss of this biotope. Accordingly, intolerance has been assessed as intermediate with a moderate recoverability (see additional information).
Changes in oxygenation
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The effects of deoxygenation in plants has been little studied. Since plants produce oxygen they may be considered relatively insensitive. However, they may be more intolerant during darkness when they continue to respire. A study of the effects of anaerobiosis (no oxygen) on some marine algae concluded that Delesseria sanguinea was very intolerant of anaerobic conditions; at 15 °C death occurs within 24hrs and no recovery takes place although specimens survived at 5 °C (Hammer, 1972). Low concentrations of dissolved oxygen may be detrimental, especially to sedentary benthic epifauna and some species of red algae. A reduction in dissolved oxygen levels to 2mg/l will probably adversely affect several members of the epifauna and holdfast fauna, although this may be a rare occurrence in exposed conditions.

Biological Factors

Introduction of microbial pathogens/parasites
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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. Echinus esculentus 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. Bald sea-urchin disease was recorded from Echinus esculentus on the Brittany Coast and, although associated with mass mortalities of Strongylocentrotus franciscanus in California and Paracentrotus lividus in the French Mediterranean (Bower, 1996), no evidence of mass moralities of Echinus esculentus associated with disease have been recorded in Britain and Ireland.
Introduction of non-native species
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The Japanese kelp Undaria pinnatifida(wakame) has recently spread to south coast of England from northern Brittany and it thought to compete with native Saccorhiza polyschides. Macrocystis pyrifera was briefly introduced to French waters, for aquaculture, before it was stopped by international pressure. Macrocystis pyrifera is large and rapid growing and could potentially compete with native kelp species (Birkett et al., 1998b) resulting in different biotopes.
Extraction
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Both Laminaria hyperborea and Echinus esculentus may be extracted. Removal of urchin predators such as lobsters or crawfish has been implicated in increases in urchin populations and therefore 'urchin barrens' and the loss of kelp beds. Similarly removal of grazing abalone by fishing is thought to have resulted in the loss of kelp beds as sea urchins populations benefited from reduced competition for food. However, attempts to correlate sea urchin numbers with specific predators are equivocal (Elner & Vadas, 1990; Birkett et al., 1998; Raffaelli & Hawkins, 1999). It is likely that there is a complex interaction between sea urchin numbers, recruitment and predation. Populations of Echinus esculentus, for example, are probably controlled by several predators, parasites, disease and recruitment. However, removal of predators or other grazers may perturb the community, making it more intolerant of natural fluctuations in sea urchin numbers or other perturbations and may result in loss of areas of kelp and 'urchin barrens'. However, extraction of Echinus esculentus may encourage dominant macroalgae, including kelps, and reduce the species richness of epiphyte and understorey fauna and flora.

Overall, an intolerance of intermediate has been suggested with a moderate recovery. Research on harvested populations of Laminaria hyperborea in Norway suggest that epiphytic and understorey fauna and flora were reduced in harvested areas compared to areas 10 years post harvesting (Sivertsen, 1991and Rinde et al., 1992, cited in Birkett et al., 1998b). Likewise recovery of the community may take at least 10 years (see 'General biology' page).

Additional information icon Additional information

Recoverability
Although the kelp plants themselves may recover in 3-4 years, the community as a whole will take at least 10 years to return (Kain, 1979; Birkett et al., 1998b). Therefore, recoverability of the biotope from factors to which it has a high intolerance (and, in some cases, intermediate intolerance), will be moderate.

Wave exposed kelp forests with dense foliose seaweeds are likely to be more intolerant of incremental grazing presence and to reduction in wave exposure.


This review can be cited as follows:

Tyler-Walters, H. 2005. Laminaria hyperborea with dense foliose red seaweeds on exposed infralittoral rock.. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21/12/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=171&code=1997>