Biodiversity & Conservation

SS.SMx.CMx.ClloMx

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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The species in the biotope are burrowing and will be lost if the substratum is removed so the overall intolerance of the biotope is high. Recovery could be very slow and is reported to be moderate - see additional information for full rationale.
Smothering
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Several species in the biotope, including the anemones, feed at the sediment surface and will be completely smothered by 5 cm of sediment. Many of the species are able to move by a limited amount and may be able to rise above the smothering material. For example, Cereus pedunculatus can adapt to the accretion of silt by extending the column to maintain the disc at a level above the silt. However, it is also likely that some species may die and so intolerance is reported to be intermediate. See additional information for recovery.
Increase in suspended sediment
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The species in the biotope are epibenthic organisms so are likely to be affected by some natural changes in suspended sediment in the water column. Increases in suspended sediment may interfere with feeding and an energetic cost may result from efforts to clean off silt particles, e.g. through mucus production and sloughing. Repeated energetic expenditure in cleaning away silt particles may cause loss of condition and a reduction in growth and fecundity. If suspended sediment has a high organic content food availability could improve. However, the overall effects of a one month acute increase in suspended sediment are sub-lethal so intolerance is reported to be low. Recovery will be rapid as particles are cleaned away.
Decrease in suspended sediment
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A decrease in suspended sediment and siltation will reduce the flux of particulate material to the seabed. Since this may also include a component of organic matter the supply of nutrients to the biotope could be reduced reducing growth and fecundity. However, the benchmark is a reduction in suspended sediment of 100mg/l for a month which is unlikely to have a significant effect on the biotope and would not alter species composition. Intolerance is therefore, assessed as low. On return to normal conditions, recovery will be rapid and rank of very high is recorded.
Desiccation
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The biotope is a sublittoral community and so a change in desiccation is not relevant.
Increase in emergence regime
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The biotope is a sublittoral community and so an increase in emergence is not relevant.
Decrease in emergence regime
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The biotope is sublittoral so a decrease in emergence is not relevant.
Increase in water flow rate
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Eleftheriou & Basford (1983) observed Cerianthus lloydii feeding under a wide range of hydrodynamic conditions which showed a great degree of adaptation to the prevailing conditions. Under conditions of heavy swell, Cerianthus lloydii exhibited behaviour to minimize drag by clumping tentacles in a semi-expanded state with the animal progressively withdrawing into the tube as velocity increased. When a threshold of between 2 and 3 knots was reached the species withdrew totally into the tube. Therefore, the species can tolerate some increase in water flow rate however, if water flow increases to strong then Cerianthus lloydii will be unable to feed and if such an increase lasted for a year the species would probably die. The athenarian burrowing anemones in the biotope however, prefer stable sediments that are rarely disturbed by strong water. Therefore, an increase in water flow rates is likely to result in the loss of many species of anemone reducing species diversity. Intolerance is therefore, reported to be high. See additional information for recovery.
Decrease in water flow rate
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The biotope is found in areas of moderately strong and weak tidal currents so is not likely to be very intolerant of a decrease in water flow. The supply of food particles may decrease in low flow conditions but this should only affect sub-lethal processes of growth and reproduction so intolerance of the biotope is expected to be low. The species composition within the biotope may change. On return to pre-impact conditions normal growth etc. should recover rapidly.
Increase in temperature
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There is no information on the response of the biotope to an increase in temperature. The biotope is found in the shallow sublittoral where the temperature may fluctuate by about 10°C over the period of a year because of seasonal changes. Therefore, the biotope is likely to be able to tolerate a long term increase in temperature. For example, Cereus pedunculatus is a southern species extending north into Britain so it will probably be able to tolerate an increase. However, other species may be more intolerant. Also intolerance to a short term increase of 5°C may be higher. The overall effect of an increase in temperature is likely to be the loss of the more intolerant species reducing species diversity y and so intolerance is reported to be intermediate. See additional information below for recovery.
Decrease in temperature
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There is no information on the response of the biotope to a decrease in temperature. The biotope is found in the shallow subtidal where temperatures may fluctuate by 10°C over the period of a year because of seasonal changes. Therefore, the biotope is expected to be able to tolerate a long term decrease in temperature of 2°C. Some of the warmer water southern species such as Cereus pedunculatus may be more intolerant and large short term increases may be more damaging. During the severe winter of 1962-3 many Cereus pedunculatus were found to have died although Cerianthus lloydii were apparently unaffected (Crisp, 1964). The survival of Cerianthus lloydii is consistent with a distribution that extends as far north as Greenland. Therefore, the overall effect of a decrease in temperature on the biotope is the loss of the more intolerant species leading to a loss of species diversity and so intolerance is reported to be intermediate. See additional information below for recovery.
Increase in turbidity
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An increase in turbidity, reducing light availability may reduce primary production by phytoplankton in the water column. However, productivity in the IMX.An biotope is secondary (zooplankton) and is not likely to be affected by an increase in local turbidity and so the biotope is considered to be not sensitive.
Decrease in turbidity
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A decrease in turbidity, increasing light availability may reduce primary production by phytoplankton in the water column. However, productivity in the IMX.An biotope is secondary (zooplankton) and is not likely to be affected by an increase in local turbidity and so the biotope is considered to be not sensitive.
Increase in wave exposure
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The biotope is found in sheltered or very sheltered locations and would therefore, be expected to be intolerant of an increase in wave exposure. The burrowing athenarian anemones in particular only survive in fairly stable substrata. An increase in wave exposure would probably mobilize the sediment and make it unsuitable for some of the anemones. However, cerianthids, such as Cerianthus lloydii, live in permanent tubes and can exist in relatively unstable substrata. Thus, an increase in wave exposure is likely to favour cerianthid anemones and lead to a much lower diversity of species. Intolerance of the biotope is therefore, considered to be intermediate. Recovery to original diversity may be very slow and a rank of moderate is reported - see additional information below for full rationale of recovery.
Decrease in wave exposure
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The biotope is found in sheltered or very sheltered locations so a decrease in wave exposure is not relevant.
Noise
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Anemones are not known to possess a mechanism for the perception of noise. However, they may respond to vibrations caused by noise by retracting tentacles or withdrawing into a burrow. In investigations of several species of burrowing actinaria, Ellehauge (1978) found sudden movements in the water made animals contract. However, intolerance will not be significant and a rank of low is reported. Recovery will be immediate.
Visual Presence
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Anemones have no known mechanism for visual perception and are not likely to be sensitive to the factor. In investigations of several species of burrowing actinarian Ellehauge (1978) found that light or shadow did not evoke a withdrawal response.
Abrasion & physical disturbance
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Burrowing and tube dwelling infauna, such as burrowing anemones, may be less affected by dredging than other epifauna (Gubbay & Knapman, 1999). In a study carried out in the Skomer Marine Nature Reserve the numbers of sea anemones, Cerianthus lloydii and Mesacmaea mitchellii, within and alongside dredge paths were similar to pre-dredge levels several weeks later. However, the biotope includes several epifaunal species, such as the encrusting anemone Epizoanthus couchii, hermit crabs, scallops and brittlestars. Epifauna is likely to be damaged and the sediment changed by a passing scallop dredge (see benchmark). Therefore, while several characterizing species are probably tolerant of physical disturbance, a proportion of other species may be damaged or lost, and an intolerance of intermediate has been recorded. Withdrawn burrowing anemones are likely to reappear and dislodged individuals reburrow. However, other sea anemone species are probably slow to recover (see additional information below). Damaged anemones may be subject to predation by fish or other animals.
Displacement
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Cerianthid anemones are capable of burrowing again and constructing a new tube if dug up. The other burrowing anemones do not build tubes and therefore, to a greater or lesser extent, are able to shift their position. Thus, if displaced the anemones in the biotope should be able to re-burrow. Peachia hastata for example, is able to reburrow in about one hour (Trueman & Ansell, 1969). The time taken for some other species, such as Cerianthus lloydii, to reburrow is longer and may place individuals at greater risk of predation. Although anthozoans do not feature prominently on the menu of many predatory animals they have been found amongst the stomach contents of fish. Most other species likely to occur in the biotope, for instance worms and bivalve molluscs, will be able to reburrow. However, the intolerance of the biotope is reported to be low because it is likely that many individuals can re-burrow and survive displacement. Recovery is expected to be immediate as individuals are likely to re-burrow as soon as they have been displaced.

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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Insufficient information.
Radionuclide contamination
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Insufficient information.
Changes in nutrient levels
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Pearson & Rosenberg (1978) observed Cerianthus lloydii and other cerianthid anemones to be present in areas at the edges of grossly and highly organically polluted sites. Therefore, an increase in nutrient levels of 50% is not likely to cause the loss of cerianthid anemones and so intolerance is reported to be low. Some other types of anemones may be more intolerant of nutrient increases leading to a decline in diversity.
Increase in salinity
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Several of the anemone species in the biotope are also found in rock pools where salinity is likely to be variable because of precipitation and evaporation. However, the biotope is unlikely to be able to tolerate a long term increase in salinity and so a rank of high is reported. See additional information for recovery.
Decrease in salinity
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The biotope is subtidal and found in areas of full salinity so may be intolerant of a decrease. However, some species of anemone, such as Cereus pedunculatus, are sometimes found at the mouth of estuaries and in Danish waters Cerianthus lloydii inhabits salinities in the range 17 to 34 psu. Several species are also found on the lower shore where salinity is variable because of precipitation and evaporation. Therefore, many of the species in the biotope must have some tolerance to short term decreases. However, a long term decrease is likely to result in a significant loss of species diversity and so intolerance is reported to be intermediate. Recovery could take a long time and is assessed as moderate - see additional information below for full rationale.
Changes in oxygenation
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Some infaunal species which require ventilation of burrows may be adversely affected by a drop in oxygenation levels. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l. There was no information found regarding the tolerance of sea anemones to a decrease in the oxygenation of the water column. However, anemones are very slow growing and are likely to have a very low metabolic rate. An oxygenation level of 2 mg/l for a period of a week may have an impact on the biotope and so intolerance is considered to be low. Recovery will be rapid as oxygen levels increase.

Biological Factors

Introduction of microbial pathogens/parasites
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No known viral or bacterial diseases are known to occur among marine cnidarians (Kinne, 1980). However, even though a number of cnidarians are capable of secreting antimicrobial substances it is possible that such diseases could occur.
Introduction of non-native species
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There are no records of any non-native species invading the biotope and so is assessed as not sensitive. However, as several species have become established in British waters there is always the potential for new introduced non-native species to have an effect on the biotope.
Extraction
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It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction. However, the biotope may be indirectly affected through the extraction of other species. Burrowing and tube dwelling infauna, such as burrowing anemones, may be less affected by dredging than other epifauna (Gubbay & Knapman, 1999). In a study carried out in the Skomer Marine Nature Reserve the numbers of sea anemones, Cerianthus lloydii and Mesacmaea mitchellii, within and alongside dredge paths were similar to pre-dredge levels several weeks later. However, the biotope includes several epifaunal species, such as the encrusting anemone Epizoanthus couchii, hermit crabs, scallops and brittlestars. Epifauna is likely to be damaged and the sediment changed by a passing scallop dredge. Therefore, while several characterizing species are probably tolerant of physical disturbance, a proportion of other species may be damaged or lost, and an intolerance of intermediate has been recorded. Withdrawn burrowing anemones are likely to reappear and dislodged individuals reburrow. However, other sea anemone species are probably slow to recover (see additional information below). Damaged anemones may be subject to predation by fish or other animals. Overall, an intermediate intolerance has been suggested with a moderate recovery (see additional information).

Additional information icon Additional information

Recoverability
There is very little known of the community development or recovery of this biotope. In addition very little is known of the life history and population dynamics of British sea anemones. However, many are slow growing and very long lived and it is possible that they have patchy and intermittent recruitment. For example, in many localities burrowing anemones were lost with the disappearance of eel-grass beds in the 1930's have not returned despite the recovery of Zostera in some regions (Manuel, 1988). Therefore, it seems likely that a community of burrowing anemones could take many years to develop and recover from environmental perturbations. Many anemones can reproduce asexually and such budding could significantly aid recovery. However, the cues for asexual reproduction are unknown. Some species also brood their young releasing miniature anemones into the water column so recruitment may be more rapid in areas where local adult populations are still present.

This review can be cited as follows:

Hill, J.M. 2001. Burrowing anemones in sublittoral muddy gravel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 24/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=8&code=2004>