Biodiversity & Conservation

SS.IGS.FaG.HalEdw

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Removal of the substratum would result in loss of the biotope, therefore intolerance is recorded as high. The biotope is rarely recorded suggesting that prospects for recovery from nearby populations of characteristic species might be low.
Smothering
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The species most likely to be affected by smothering are the epibiota of sessile animal and algal species that recruit from the plankton and would probably recolonize rapidly. The burrowing species in the sediment (which are the species most likely to be long-lived and slow to recover) are most likely capable of remaining retracted for considerable periods or could burrow upwards through smothering sediment. The fan worm Sabella pavonina would protrude above smothering sediment. If smothering caused deoxygenation, a higher intolerance and lower recoverability would be recorded.
Increase in suspended sediment
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Increase in suspended sediment may bring additional food for suspension feeders but may have adverse effects in clogging feeding structures and reducing light penetration. On balance, not sensitive at the benchmark level is suggested.
Decrease in suspended sediment
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Decrease in suspended sediment may reduce the food supply for suspension feeders but may allow increased light penetration and therefore improve prospects for algal growth. On balance, not sensitive is suggested.
Desiccation
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The biotope is subtidal and therefore desiccation is not relevant.
Increase in emergence regime
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The biotope is subtidal and therefore emergence regime is not relevant.
Decrease in emergence regime
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The biotope is subtidal and therefore emergence regime is not relevant.
Increase in water flow rate
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Increased tidal stream velocity may benefit some passive suspension feeders by increasing the supply of food but may also erode the substratum including removal of species attached to the substratum. The long-lived members of the community, the burrowing anemones, are firmly anchored into the sediment and therefore are unlikely to be lost. Removal of the fine grain components of the sediment is likely to be permanent and the biotope is likely to be changed to a different one. As change in biotope will be permanent, intolerance is considered to be high and recoverability very low.
Decrease in water flow rate
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Decreased water flow rate is likely to reduce food supply for passive suspension feeders and allow deposition of fine sediment. Some smothering might occur leading to loss of individuals of species. The long-lived burrowing anemones are unlikely to be affected except perhaps by less food being brought to them. Therefore an intolerance and recoverability of high have been recorded. On resumption of a normal flow regime the minority of species that may have been lost will recolonize from the plankton.
Increase in temperature
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The species living attached to the substratum have a wide distribution in the NE Atlantic and the burrowing anemones appear to be southern in their distribution. Therefore, it is not expected that acute or moderately long-term increase in temperature will have an adverse effect.
Decrease in temperature
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Some of the species in the biotope are known to be adversely affected by an acute decrease in temperature. Sabella pavonina and Megalomma vesiculosum (as Branchiomma vesiculosum) were both severely affected by the cold winter of 1962-63 (Crisp, 1964). The burrowing sea anemones characteristic of the biotope occur from Scotland southwards and may be considered warm water species. However, adults are likely to survive long-term decrease in temperature and it is reproduction and recruitment that is likely to be adversely affected. The species most likely to be affected by cold recruit from the plankton and would recolonize within a few years. Therefore an intolerance of intermediate has been recorded.
Increase in turbidity
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The main effect of increase in turbidity is likely to be a decrease in the abundance of algae in the biotope. For ephemeral species, increased turbidity at the time spores are settling and developing may lead to less algae in that year. In the case of a longer-term increase in turbidity, some perennial species may demise and grazing species may be adversely affected. However, algae settle from the plankton and recovery is likely to be rapid.
Decrease in turbidity
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Decreased turbidity and therefore increased light penetration is likely to lead to an increase in the abundance of algae in the biotope. Whilst providing food for grazing species, algae may smother some species or reduce their ability to suspension feed. Once established, algae will remain in the biotope but will be lost as a part of the seasonal cycle so that recoverability is very high.
Increase in wave exposure
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The biotope occurs in moderately exposed or sheltered locations most likely where tidal flow is more important than wave action as a structuring factor. Increase in wave exposure may result in displacement of the substratum with consequent scouring. Over one year, sufficient of the substratum might be lost so that the biotope changes to a different one. However, the long-lived members of the community, the burrowing anemones, are firmly anchored into the sediment and therefore are unlikely to be lost. As change to a different biotope will be permanent, intolerance is considered to be high and recoverability very low.
Decrease in wave exposure
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The biotope occurs in moderately exposed or sheltered locations most likely where tidal flow is more important than wave action as a structuring factor. Reduction in wave action is therefore unlikely to have an effect unless cessation of periodic disturbance caused by storms allows one or few species to become dominant to the exclusion of other species. It is more likely that increased stability will allow development of a richer community typical of areas exposed to tidal flow.
Noise
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Whilst species such as Sabella pavonina and Megalomma vesiculosum may be intolerant of vibration and withdraw, no species in the biotope are known to be able to detect noise.
Visual Presence
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Species such as Sabella pavonina and Megalomma vesiculosum may be intolerant of shadowing and withdraw. However, they re-expand rapidly.
Abrasion & physical disturbance
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The biotope would be intolerant of physical disturbance that scraped pebbles or turned them over so that attached species became smothered. However, it is likely that the burrowing anemones would withdraw into the sediment to avoid the factor and therefore have a low intolerance. Species living on the pebbles have planktonic larvae and would probably recolonize rapidly.
Displacement
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The important characterizing species are sedentary but capable of re-burrowing. Therefore adverse effects would be short-term and recovery would be likely to be rapid.

Chemical Factors

Synthetic compound contamination
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Insufficient information.
Heavy metal contamination
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Insufficient information.
Hydrocarbon contamination
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Information has been found on only one of the species mentioned in the biotope description, Urticina felina. Smith (1968) mentions that Urticina felina seemed unaffected during the Torrey Canyon oil spill. However, information on more species is required before an assessment can be made.
Radionuclide contamination
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No information found.
Changes in nutrient levels
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No information found.
Increase in salinity
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The biotope is recorded from full salinity subtidal situations. Increase in salinity is not likely.
Decrease in salinity
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The biotope is recorded from full salinity situations. It occurs in sea lochs where some dilution of water would be expected during heavy rain and where mixing occurs. However, component algal species are likely to be adversely affected by decreased salinity. Others, such as Sabella pavonina and Megalomma vesiculosum occur in estuarine situations. No information has been found on the likely intolerance of the burrowing anemones. Species that are known to be likely to be affected have planktonic propagules and so are likely to recover fairly rapidly. Therefore an intolerance of intermediate and recoverability of high have been recorded.
Changes in oxygenation
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The biotope occurs in areas where tidal flow is generally moderate and, therefore, oxygenation is good. Decrease in oxygenation due to stagnation or smothering is likely to have an adverse effect on a community attuned to well-oxygenated conditions. However, as the burrowing anemones most likely spend significant periods of time in stagnant burrows, they may be expected to be tolerant of low oxygen conditions at the benchmark level of 2mg per litre for one week. Therefore, although some species may perish, those unlikely to recover rapidly are thought likely to survive.

Biological Factors

Introduction of microbial pathogens/parasites
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No information found.
Introduction of non-native species
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No alien species are known to occur in this biotope and therefore an assessment of not sensitive is given. However, future spread of species currently in Britain or new arrivals may change this assessment.
Extraction
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It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction and we have no evidence for the indirect effects of extraction of other species on this biotope.

Additional information icon Additional information

No additional information entered.

This review can be cited as follows:

Hiscock, K. 2001. Halcampa chrysanthellum and Edwardsia timida on sublittoral clean stone gravel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 23/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=80&code=1997>