Biodiversity & Conservation

CR.FCR.Cv

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Removal of the substratum will remove the sessile fauna that characterizes this biotope. Whilst some species such as Caryophyllia smithii and branching and encrusting bryozoans are likely to colonize bare rock rapidly, others such as Leptopsammia pruvoti and Hoplangia durotrix (K. Hiscock, own observations) and probably Alcyonium hibernicum (Hartnoll, 1977) have short lived larvae and appear to reproduce very infrequently so that recolonization is likely to take at least 25 years and may not occur at all.
Smothering
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The corals and zoanthid anemones in this biotope would mostly extend above a layer of silt or survive smothering by 5 cm of silt (the benchmark) by 'inflating' their polyps. Others, such as encrusting sponges may not survive. Encrusting bryozoans may survive: they survive overgrowth by encrusting tunicates (Turner 1988). Smothering may not be highly relevant to this biotope as it occurs on vertical and overhanging surfaces. Overall, some species in the biotope are intolerant but some important species may survive.
Increase in suspended sediment
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The species in the biotope are most likely tolerant of increases in suspended sediment. For instance, the corals have cilia on their tentacles capable of clearing silt (K. Hiscock, own observations) whilst sponges produce mucus which is discarded with silt to clear surfaces. Since the biotope occurs on vertical or overhanging rock, increased fall-out of silt being deposited on surfaces is unlikely.
Decrease in suspended sediment
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Whilst some of the species (particularly sponges) in the biotope might obtain some food from organic matter associated with suspended sediment, it is not considered a major food source.
Desiccation
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The biotope is circalittoral in Britain and Ireland and desiccation is not relevant.
Increase in emergence regime
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The biotope is circalittoral in Britain and Ireland and emergence is not relevant.
Decrease in emergence regime
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The biotope is circalittoral in Britain and Ireland and emergence is not relevant.
Increase in water flow rate
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The species present in the biotope are capable of living in strong to weak currents and, although feeding in particular might be affected, it is not thought that individuals will be killed by increases or decreases in flow rate. Recovery of condition is likely to be rapid following return to previous conditions.
Decrease in water flow rate
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The species present in the biotope are capable of living in strong to weak currents and, although feeding in particular might be affected, it is not thought that individuals will be killed by increases or decreases in flow rate. Recovery of condition is likely to be rapid following return to previous conditions.
Increase in temperature
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Many of the species that characterize this biotope are southern in distribution and increase in temperature by up to 5°C above average or normal maximum is likely to have a positive influence on reproduction. For instance, Leptopsammia pruvoti transferred from their natural habitat to aquaria have, on three occasions, produced planulae - possibly due at least in part to increased temperatures (Keith Hiscock, own observations). Even a short-term increase in temperature may therefore encourage recruitment into the community that will increase abundance of long-lived, slow-growing and infrequently recruiting species considerably.
Decrease in temperature
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Decrease in temperature is unlikely to affect survival of established individuals although there is little direct evidence for characteristic species. Lower temperatures may adversely affect prospects for successful production of propagules and therefore long-term survivability. However, as reduction in temperature at the benchmark level is for only one year, long-term prospects for the biotope are likely to be unaffected.
Increase in turbidity
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Species in the biotope do not depend on light and so increase in turbidity is not likely to have an adverse effect.
Decrease in turbidity
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Decrease in turbidity may result in increased light levels but, in the vertical and overhanging habitats in which the biotope occurs, it is unlikely that there would be any algal growth and not smothering growth.
Increase in wave exposure
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The species present in the biotope are capable of living in strong to weak wave action and, although feeding in particular might be adversely affected by increased or wave strength, it is not thought that individuals will be killed except where the biotope is already in a top-of-the-range situation where increased wave action may cause mortality of species. This mortality may especially be the case where the skeleton of cup corals is weakened by boring organisms. Recovery of condition is likely to be rapid following return to previous wave action although, if a proportion of corals have been lost, the population is unlikely to build to previous numbers for many years.
Decrease in wave exposure
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The biotope occurs in wave sheltered conditions where wave action (for feeding or to remove silt) does not seem to be a requirement. Providing that tidal flow is sufficient to bring food in the absence of significant wave action, no adverse effects are to be expected.
Noise
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Species present in the biotope are not known to have receptors for noise and are not likely to be affected.
Visual Presence
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Species present in the biotope are not known to have visual receptors and are not likely to be affected.
Abrasion & physical disturbance
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Physical disturbance and abrasion will remove much of the sessile fauna that characterize this biotope. Whilst some species such as Caryophyllia smithii and branching and encrusting bryozoans are likely to colonize bare rock rapidly, others such as Leptopsammia pruvoti and Hoplangia durotrix and probably Alcyonium hibernicum most likely have short lived larvae and appear to reproduce very infrequently so that recolonisation is likely to take many years. However, some species such as encrusting sponges are likely to survive in concavities and fissures and regrow from there.
Displacement
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The species that characterize this biotope are sessile and displacement will involve removing them from their substratum. Whilst individual species may survive for a short time in a detached state, the biotope will no longer exist. Whilst some species such as Caryophyllia smithii and branching and encrusting bryozoans are likely to colonize bare rock rapidly, others such as Leptopsammia pruvoti and Hoplangia durotrix (Keith Hiscock, own observations), and probably Alcyonium coralloides (Hartnoll, 1977), have short lived larvae and appear to reproduce very infrequently so that recolonization is likely to take at least 25 years and may not occur at all.

Chemical Factors

Synthetic compound contamination
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No information was found on effects of synthetic chemicals on component species.
Heavy metal contamination
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No information was found on effects of heavy metals on component species.
Hydrocarbon contamination
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No information was found on effects of hydrocarbons on component species.
Radionuclide contamination
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No information was found on effects of radionuclides on component species.
Changes in nutrient levels
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No information was found on effects of nutrients on component species.
Increase in salinity
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The biotope occurs on the open coast in normal salinity. An increase in salinity would not be expected.
Decrease in salinity
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This biotope only occurs in open coastal and offshore areas and it is expected that lowered salinity will have an adverse effect on species in the biotope and will result in the death of the sessile fauna that characterizes this biotope. Whilst some species such as Caryophyllia smithii and branching and encrusting bryozoans are likely to recolonize rapidly, others such as Leptopsammia pruvoti and Hoplangia durotrix (K. Hiscock, own observations) and probably Alcyonium hibernicum (Hartnoll, 1977) have short lived larvae and appear to reproduce very infrequently so that recolonization is likely to take at least 25 years and may not occur at all.
Changes in oxygenation
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Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. The biotope lives on the open coast in normally good water exchange conditions. Whilst some species or individuals of some species may survive deoxygenation, the biotope will most likely no longer exist. Whilst some species such as Caryophyllia smithii and branching and encrusting bryozoans are likely to recolonize the habitat rapidly, others such as Leptopsammia pruvoti and Hoplangia durotrix (K. Hiscock, own observations) and probably Alcyonium hibernicum (Hartnoll, 1977) have short lived larvae and appear to reproduce very infrequently. As the species has not been observed to colonize apparently suitable new habitats such as wrecks or the Plymouth breakwater, it seems that recolonization from distant populations is unlikely. Hoplangia durotrix (K. Hiscock, own observations) and Alcyonium hibernicum (Hartnoll, 1977) at least are believed to have similar reproductive infrequencies and short larval life span so that recolonization is likely to take at least 25 years and may not occur at all.

Biological Factors

Introduction of microbial pathogens/parasites
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No information has been found on effects of microbial pathogens.
Introduction of non-native species
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There are no non-native species currently (November 2001) known to colonize this biotope.
Extraction
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Although extraction does not occur at present, the assessment here is for possible extraction, for instance for the aquarium trade. In this case, intermediate intolerance has been suggested to reflect the possibility that some species may be targeted. Recovery is based on the likelihood that a proportion of the population would be left behind, grow and reproduce. However, species such as Leptopsammia pruvoti and Hoplangia durotrix (K. Hiscock, own observations) and probably Alcyonium hibernicum (Hartnoll, 1977) have short lived larvae and appear to reproduce very infrequently so that recolonization is likely to take up to 25 years. The biotope would remain but possibly as an impoverished example.

This review can be cited as follows:

Hiscock, K. 2000. Caves and overhangs (deep). Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 22/09/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=10&code=2004>