Biodiversity & Conservation

SS.CMS._.Ser

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Serpula vermicularis forms reefs by attachment to the substratum and so will be highly intolerant of removal of the substratum. The sessile epifauna associated with the reefs, such as ascidian, hydroids and bryozoans, will also be removed. Some mobile species, such as fish and crabs, may be able to escape, but many are slow moving and will also be lost if substratum is removed. Intolerance of the biotope is therefore, high. Recovery from complete loss of reefs is likely to take a very long time, if at all, and a rank of very low is reported, resulting in a very high sensitivity rating - see additional information for full rationale.
Smothering
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Serpula vermicularis is permanently attached to the substratum by a calcareous tube which in aggregating reef forming individuals extends above the substratum as new worms are added to old tubes. For example, in Loch Creran individual reefs are reported to reach a height of about 75cm (Moore, 1996). The reef structure is also very open, creating cracks and crevices where sediment could collect. Therefore, many individuals of Serpula vermicularis, and the associated fauna of sponges, ascidians and hydroids, may avoid 5cm of smothering material. Some of the mobile species in the biotope may be able to avoid the factor. However, a portion of the reef may be lost so intolerance is reported to be intermediate. In addition, it is also likely that too much sediment on the surface of rocks or tubes would prevent settlement of larvae (Holt et al., 1998) and so may also reduce the long term growth of the reef. As individuals of Serpula vermicularis remain alive and the hard substratum of the reef is available for settlement of new individuals recovery is reported to be high, hence sensitivity is low - additional information below for full rationale.
Increase in suspended sediment
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Siltation can have a negative impact on site selection by larvae (Rodriguez et al., 1993). Bosence (1979b) concluded from observations and from transplant experiments, that the lower depth limit of Serpula vermicularis was probably determined by suspended sediment and de-oxygenation. In contrast Moore et al. (1998b) found no horizontal layers of suspended mud in Loch Creran, and although the authors do not rule out the possibility that storm-generated, suspended mud may inhibit reef development, the lower limit of reefs could also be due to inadequate current velocities for suspension feeding. Chapman et al., (2007) suggested that the lower depth limit was a result of depth-correlated settlement response of larvae.
A supply of suspended sediment may be important to Serpula vermicularis because the species requires a supply of particulate matter for suspension feeding. However, at the benchmark level of an increase of 100mg/l for one month, the likely impact would be an increase in cleaning costs. Thus, the biotope is not likely to be significantly affected and a rank of low is reported. Other suspension feeding species in the biotope may be more intolerant of suspended sediment levels, although at the level of the benchmark, effects are likely to be largely sub-lethal. Recovery will be immediate as normal feeding returns on the resumption of pre-impact conditions. Other species that may be lost are likely to recolonise rapidly. Hence a suggested sensitivity ranking of not sensitive.
Decrease in suspended sediment
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A supply of suspended sediment for feeding is probably important to Serpula vermicularis and other suspension feeders in the biotope. However, the species is an active suspension feeder creating its own feeding currents so is not likely to be highly intolerant of changes in suspended sediment. Bosence (1979b) also suggests that increases in suspended sediment limit the distribution of Serpula vermicularis, so a decrease is not expected to be detrimental. Other species in the biotope are not likely to be significantly affected by a decrease for a month. Therefore, a rank of low is reported and recovery will be very rapid, resulting in a rank of not sensitive.
Desiccation
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The biotope is found in the circalittoral and so desiccation is not a relevant factor.
Increase in emergence regime
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The biotope is found in the circalittoral and so emergence is not a relevant factor.
Decrease in emergence regime
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The biotope is found in the circalittoral and so emergence is not a relevant factor.
Increase in water flow rate
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Reefs appear to occur mainly in areas sheltered from strong water flow. For example, in Loch Creran no reefs were recorded in the outer section of the loch beyond the narrows at Sgeir Calliach, despite the presence of suitable depths and substrates. This is a well-flushed section of the loch, where the larvae of Serpula vermicularis will presumably be at lower concentrations than further up the loch (Moore, 1998b). Therefore, the biotope will be intolerant of an increase in water flow rate as larvae are likely to be taken away from the reefs, old worms will die and without a supply of new individuals the reef will die. With the collapse of dead Serpula reefs, species diversity will decline significantly because the open structure of the reefs provides substratum and crevices for many other organisms. Intolerance of the biotope is therefore, set to high. Recovery from complete loss of reefs is unlikely or at best very slow, so suggested recoverability is very low, resulting in a high sensitivity rating - see additional information.
Decrease in water flow rate
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Serpula vermicularis reefs only develop in sheltered areas where there is little water movement and larvae are thought to be prevented from being carried away. Therefore, since populations can survive in low water flow environments intolerance is reported to be low. However, a reduction in water flow may reduce food supply although this will probably not have a huge impact on the suspension feeding Serpula vermicularis because the species can generate its own feeding currents. Reduced water flow may allow the deposition of silt which is thought to create unfavourable conditions for the settlement of larvae (Cotter et al. 2003). On return to normal conditions, recovery would be quick so is deemed very high, hence a very low sensitivity rating.
Increase in temperature
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Serpula vermicularis has a broad geographical range which suggests that it is tolerant of some temperature change. In Loch Creran in Scotland, the temperature regime within the main basin is similar to that in the adjacent sea with a low of about 6°C in February/March and a high of 13 - 15°C in August/September (Gage, 1972). The peak in larval recruitment of Serpula vermicularis in loch Creran coincides with this peak in temperature (Chapman et al., 2007). Additionally, Hughes et al., (2005) found the species to be tolerant of changes in temperature “with upper lethal limits exceeding any value that they could conceivably experience in the field”. Therefore a rank of low intolerance is reported. Some other species in the biotope may be more intolerant of increases in temperature although overall species diversity is not expected to be significantly affected. Recoverability is likely to be high provided larval supply is adequate, so recoverability is rated as low, giving a low sensitivity rank.
Decrease in temperature
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Serpula vermicularis has a broad geographical range which suggests that it is unlikely to be very intolerant of temperature changes. It would be expected that in shallow enclosed areas, temperature will fall during periods of cold winter weather so decreases in temperature are probably tolerated by reefs. Hughes et al., (2005) found the species to be tolerant of a wide range of temperatures, therefore a rank of low intolerance is reported. Some other species in the biotope may be more intolerant of decreases in temperature although overall species diversity is not expected to be significantly affected. Recoverability is likely to be high provided larval supply is adequate, so recoverability is rated as low, giving a low sensitivity rank.
Increase in turbidity
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An increase in turbidity, reducing light availability, may reduce primary production by phytoplankton in the water column. Tett and Edwards (2002) noted that the level of phytoplankton abundance in Loch Creran is high for Scottish coastal waters, and it has been suggested that high food availability (Ten Hove, 1979) and increased primary productivity (Bosence, 1979) may contribute to reef formation. However, productivity in the CMS.Ser biotope is predominantly secondary (detritus based) and although an increase in turbidity may reduce the phytoplankton contribution to detritus, any effects at the level of the benchmark, are not likely to be significant. There are some red algae present in the biotope and so an increase in turbidity may reduce photosynthesis and growth because of light attenuation. However, this is not likely to affect the nature of the biotope and so intolerance of the biotope is assessed as low. On return to normal conditions recovery would be swift, hence a rating of very fast, and therefore a sensitivity of very low.
Decrease in turbidity
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A decrease in turbidity will increase light availability which could improve levels of primary production. Phytoplankton in the water column may become more abundant at certain times of the year improving overall food supplies for suspension feeders. It has been suggested that increased food supply (Ten Hove, 1979) and increased primary productivity (Bosence, 1979) may contribute to reef formation. An improvement in light availability may also lead to an increase in the growth of algae which may be able to out-compete Serpula vermicularis in the colonization of hard surfaces. However, a decrease in turbidity for a month is not likely to have a significant impact on the biotope so intolerance is reported to be low. On return to normal conditions recovery would be swift, hence a rating of very fast, and therefore a sensitivity of very low.
Increase in wave exposure
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In the sheltered areas such as sea lochs, where Serpula vermicularis aggregates to create reefs, the species grows upwards and outwards. The reefs are fairly open and quite fragile and so are likely to be intolerant of wave exposure, and no reefs are reported at depths of 0 m, which may be the effect of turbulence on larval recriutment (Champan et al., 2007). Loss of the reefs will also result in a major loss of species diversity. However in sea lochs a change in wave exposure is unlikely to occur other than over geological timescales, therefore sensitivity is assessed as not relevant. See additional information for recovery information.
Decrease in wave exposure
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The biotope occurs in very sheltered sea lochs where wave exposure is minimal and so is not likely to be sensitive to a decrease. In sea lochs a change in wave exposure is unlikely to occur other than over geological timescales, therefore sensitivity is assessed as not relevant.
Noise
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At the level of the benchmark Serpula vermicularis, or any of the associated species, are not likely to be sensitive to noise but may respond to the vibrations associated with noise as a predator avoidance mechanism. However, at the level of the benchmark reefs will not be sensitive to noise.
Visual Presence
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Serpula vermicularis has been observed to react to the visual presence of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans). It is sensitive to a sudden decrease in light levels as a predator avoidance mechanism (Poloczanska et al., 2004). Also, in areas popular with SCUBA divers, it is possible that flash photography may result in a reduction in feeding, as grey literature reports that light stimuli cause the retraction of feeding apparatus. However, at the level of the benchmark this is not thought to affect the biotope and tolerant is the suggested sensitivity level.
Abrasion & physical disturbance
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Serpula vermicularis are fragile and can be easily damaged. For example, in Loch Creran severe damage, although only on a local scale, was caused by movement of mooring blocks and chains (Moore, 1996). Although the effects were localized, mooring had reduced colonies to rubble within a radius of 10 m in one instance, and extensive damage was reported within 50 m of salmon cages (Holt et al., 1998). Holt et al. (1998) suggested that fishing activity could be very damaging but that no evidence of damage had yet been observed. Although individual worms survived and were seen to continue feeding, the reefs were broken up so that the value of the habitat was greatly diminished. A passing scallop dredge is likely to result in more damage. In Loch Creran individual reefs are reported to reach a height of about 75cm and 1m across, although adjacent reefs may coalesce to form larger reefs up to 3m across (Moore, 1996). In either case, a passing beam trawl or scallop dredge could destroy the entire reef. Intolerance of the biotope is therefore, reported to be high. Pieces of reef broken off from the main reef may continue to grow as new worms attach to fragments (Bosence, 1979b). Therefore, as individuals will remain, the re-establishment of reefs is possible and so recovery is reported to be high, and sensitivity moderate - see additional information below.
Displacement
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Serpula vermicularis lives in a calcareous tube that is permanently attached to the substratum. It is unlikely that the worm is able to rapidly build a new tube if displaced and so would probably die. Many of the other species in the biotope are also sessile, usually attached to the reef, so will also be unable to reattach if displaced. Intolerance is therefore, reported to be high. See additional information for recovery, which is rated very low, giving a very high sensitivity rating.

Chemical Factors

Synthetic compound contamination
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Insufficient information.
Heavy metal contamination
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Serpula vermicularis was found at Garric Roads, close to Restronguet Creek in the Fal estuary, that is contaminated with high levels of metals, in particular copper, zinc and arsenic (Bryan & Gibbs, 1983). It was also found in the laboratory that levels of mercury far higher than those naturally encountered by Serpula vermicularis are required to have a toxic effect on the species (Gray, 1976). Therefore, it appears that the species can tolerate some enhanced heavy metal concentrations and so intolerance is reported to be low.
Hydrocarbon contamination
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Insufficient information.
Radionuclide contamination
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Insufficient information.
Changes in nutrient levels
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In Loch Creran in Scotland, where Serpula vermicularis forms extensive reefs, organic effluent from an alginate factory appeared to have been responsible for eliminating reefs for a distance of about 1km and may have reduced reef development at greater distances (Moore et al., 1998b). However, this level of organic pollution was extreme, with much of the seabed becoming covered in a thick bacterial mat, and does not give any indication of the intolerance of Serpula vermicularis reefs to a benchmark increase in nutrients of 50%. Species diversity may decline but the overall impact on reefs is unknown.
Increase in salinity
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Serpula vermicularis is not found in areas where hypersaline conditions may occur, such as rock pools or lagoons, so it seems likely that the species would be intolerant of increases in salinity. A long term increase to hypersaline conditions would probably result in loss of reefs, and the loss of many of the other the other species that colonize the reefs, so intolerance is set to high but with a very low confidence. Recovery from loss of reefs is likely to be very slow if at all, hence a very high sensitivity - see additional information below.
Decrease in salinity
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Bosence (1979b) suggests that the layer of lower salinity water in the upper layers of the water in Ardbear Loch in Galway, Eire is partly responsible for the lack of individuals above a depth of 2m. However, Serpula vermicularis are known to tolerate reduced salinities (Hartmann-Schröder, 1971 and Mastrangelo & Passeri, 1975, cited in Moore et al., 1998b) and in Loch Creran in Scotland individual specimens of Serpula vermicularis were commonly observed in shallow waters were salinities can fall to around 23psu. Small enclosed lochs such as Loch Sween & Ardbear Loch are often subject to extremely variable salinity so the species seems to be tolerant of shorter term changes. Serpula vermicularis reefs were also observed in intertidal areas of Loch Creran, where salinity is likely to vary, during the 19th century. Therefore, it seems likely that the species can tolerate some decreases in salinity. However, when reduced salinity interacts with variation in temperature, larval mortality occurs (Gray, 1976). Also, long term reductions would probably reduce abundance so intolerance is set to intermediate. Some of the other species found in association with the Serpula vermicularis reefs may be intolerant of decreases in salinity leading to a possible reduction in the overall species diversity of the reef. When individuals of Serpula vermicularis remain after a perturbation, recovery should be possible and is set to high, thus sensitivity is low - see additional information below for full rationale.
Changes in oxygenation
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There is no information regarding the tolerance of Serpula vermicularis to deoxygenation. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. Bosence (1979b) observed that the lower limit of larval settlement in Ardbear Lough, Eire coincided with mud-rich and possibly oxygen poor water. Therefore, the species, and the larvae in particular, may be intolerant of deoxygenated water and a rank of intermediate is reported. Gage (1972) found the dissolved oxygen concentration in the lower basin of Loch Creran in Scotland, where Serpula vermicularis reefs form, did not fall below 87% saturation. Other species in the biotope may also be intolerant of changes in oxygen availability resulting in a possible loss of species diversity. On return to normal conditions recovery would be swift, hence a rating of very fast, and therefore a sensitivity of low.

Biological Factors

Introduction of microbial pathogens/parasites
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No information on diseases of Serpula vermicularis was found. However, the species is known to be parasitized by the protozoan Haplosporidium parisi (Ormieres, 1980) but the effects of this infestation are unknown. There are no reports of loss of the biotope from disease. However there is always the potential for this to occur.
Introduction of non-native species
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Although several species of serpulid polychaetes have been introduced into British waters none are reported to compete with Serpula vermicularis (Eno et al., 1997). However, there is always the potential for introduced species to either compete with, or prey upon Serpula vermicularis.
Extraction
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Small scale collection of Serpula vermicularis by divers for commercial aquaria takes place in Loch Creran (Moore, 1996) although it appears that this limited collection is sustainable. However, the reef areas often contain reasonable stocks of the queen scallop, Aequipecten opercularis, and there are occasional reports of shallow-water dredging in Loch Creran in Scotland (Moore et al., 1998b). Serpula vermicularis are fragile and can be easily damaged. Holt et al. (1998) suggested that fishing activity could be very damaging but that no evidence of damage had yet been observed. Although individual worms survived and were seen to continue feeding, the reefs were broken up so that the value of the habitat was greatly diminished. A passing scallop dredge is likely to result in more damage. In Loch Creran individual reefs are reported to reach a height of about 75cm and 1m across, although adjacent reefs may coalesce to form larger reefs up to 3m across (Moore, 1996). In either case, a passing beam trawl or scallop dredge could destroy the entire reef. Intolerance of the biotope is therefore, reported to be high. Pieces of reef broken off from the main reef may continue to grow as new worms attach to fragments (Bosence, 1979b). Therefore, as individuals will remain, the re-establishment of reefs is possible and so recovery is reported to be high, thus sensitivity is low - see additional information below.

Additional information icon Additional information

Recoverability
Serpula vermicularis probably reaches sexual maturity in its first year and reproduces every year thereafter. The planktonic larvae, which is thought to stay in the water column for one to eight weeks, may be able to disperse widely and so generally recovery rates of the species would be high. However, in the sheltered and enclosed areas where Serpula vermicularis forms reefs recovery may not be possible if populations are completely lost. This is because the factor that enables the reefs to develop, i.e. limited water exchange keeping larvae in the local system, also limits the supply of larvae from coastal waters to replace populations if they disappear. Therefore, if local populations of Serpula vermicularis are completely lost recovery of the key species, and therefore the biotope, will be extremely slow, if at all. So, where a factor is likely to result in complete loss of populations a recovery rank of very low has been reported. However, if individuals of Serpula vermicularis remain after a perturbation recovery of the reefs should be possible because recruitment from local populations can occur. For example, Moore (unpublished in Holt et al., 1998) found that dense aggregations of Serpula vermicularis up to about 15cm in height were present on bare substratum after 3 months, so re-establishment of reefs should be possible within five years. Therefore, if the factor is not likely to result in a complete loss of populations a recovery rank of high is reported. The other species in the biotope, such as ascidians, sponges, hydroids and other polychaetes, are likely to be iteroparous with planktonic larvae so that recovery should be possible within a few years. However, many of these species have short-lived larvae so if local populations are completely lost recovery may take longer because of the limited water exchange found in the locations where this biotope develops. Recovery of the biotope is determined primarily by the recovery of Serpula vermicularis.

This review can be cited as follows:

Hill, J.M. & Wilding C.M. 2008. Serpula vermicularis reefs on very sheltered circalittoral muddy sand. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 31/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=41&code=1997>