Biodiversity & Conservation

IR.MIR.SedK.SabKR

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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The key structural species Sabellaria spinulosa and almost all the other species, including the important structural and characterizing species (Laminaria hyperborea, Delesseria sanguinea and Lithophyllum incrustans) and the associated ascidians, sponges, hydroids and bryozoans are permanently attached to the substratum and cannot reattach if removed. Thus, substratum loss would cause the loss of the entire biotope and so intolerance is high. Recovery from total loss of the biotope could take a long time and is set to moderate - see additional information below for full rationale.
Smothering
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The biotope is found on sand influenced rock and many of the characterizing species are tolerant of some smothering by sediment. Sabellaria spinulosa, for example, requires the presence of sand grains for tube construction and Holt et al. (1998) observed that damage of adjacent populations of Sabellaria spinulosa by sediment plumes from gravel extraction was not particularly high. The similar Sabellaria alveolata can tolerate several weeks of smothering by sand (Wilson, 1971). Kelp and the red algae present in the biotope, such as Lithophyllum incrustans and Delesseria sanguinea, are also sediment tolerant and unlikely to be lost from smothering as plants can float above smothering material. However, several of the sessile species in the biotope, such as the suspension feeding ascidian Botryllus schlosseri and the sponge Halichondria panicea are likely to be damaged or killed because smothering will clog feeding and/or respiratory flows and these animals have no mechanism for expanding above smothering material. Some, most likely such as the sea anemone Urticina felina may survive smothering material providing deoxygenation does not occur. Therefore, the overall impact is that species diversity would therefore probably decline but the overall biotope should remain functionally intact if smothered for one month and so intolerance is reported to be low. On return to pre-smothered conditions recovery should be fairly rapid as organisms self clean.
Increase in suspended sediment
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The biotope occurs in high turbidity areas. The distribution of Sabellaria spinulosa in reef form appears to be restricted to areas subject to relatively high sediment loadings so the species is likely to be relatively tolerant of an increase in suspended sediment for a period of a month. Established Laminaria hyperborea are likely to be relatively tolerant of increased siltation although it may decrease photosynthetic potential for the duration of the event and 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). Most of the other species in the biotope, such as the foliose and encrusting red algae, sponges and suspension feeders also have low intolerance to suspended sediment although there may be some clogging of suspension feeding apparatus. However, for a period of a month impacts will be slight. Thus, the species composition and nature of the biotope is not likely to change so intolerance of the biotope is reported to be low and recovery will be immediate as feeding rates return to pre-impact levels.
Decrease in suspended sediment
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A decrease in suspended sediment is likely to have an impact on the biotope because the key structural species, Sabellaria spinulosa, requires sand particles to build its tubes and for its food supply. Therefore, a decline would probably result in reduced growth and worm density. Laminaria hyperborea is likely to improve in productivity as a result of decreased suspended sediment as available light increases and siltation of the fronds will not occur. Decreased siltation although it may affect holdfast fauna encouraging more species associated with clearer waters (Moore, 1973a&b; Edwards, 1980). Some of the suspension feeding species in the biotope, such as sponges, ascidians and Ophiothrix fragilis may be intolerant of reduced levels of suspended sediment as food availability is reduced. However, the benchmark decrease is only for a month so any impacts on the biotope are expected to be minimal and so intolerance is reported to be low.
Desiccation
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The biotope is predominantly sublittoral but the key structural species, Sabellaria spinulosa, is occasionally found in the intertidal (as individuals rather than dense crusts) and so has some ability to resist desiccation. The important characterizing species, kelp and red algae however, are generally sub-tidal and are highly intolerant of desiccation. Many of the other species in the biotope (e.g. Delesseria sanguinea, Botryllus schlosseri and Halichondria panicea) are found in the intertidal and have intermediate intolerance to desiccation. Exposure of the biotope to an hour of air and sunshine per day may cause the loss of some species at the upper limit of its range but the biotope as a whole would probably remain physically and functionally intact and so intolerance is reported to be intermediate. See additional information below for recovery.
Increase in emergence regime
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Sabellaria spinulosa is sessile and typically subtidal but is also occasionally found in the low intertidal. This means the species can tolerate some emergence, however, increased emergence will reduce the amount of time available for feeding and some individuals at the upper limit of the species range will probably be killed. Laminaria hyperborea is primarily a subtidal species and is likely to be highly intolerant of increases in emergence. Its upper limit on the shore is in part dependant on the emergence regime as well as competition from more tolerant species such as Laminaria digitata. Therefore, an increase in emergence is likely to depress the upper limit of this species also. Thus, the overall impact on the biotope is likely to be a depression of the upper limit of the biotope and so intolerance is reported to be intermediate. Some sessile species, such as sea squirts and sponges, are unlikely to survive a long term increase in emergence. However, in the presence of a suitable substratum the biotope is likely to re-establish further down the shore. Recovery is likely to be high – see additional information for recovery.
Decrease in emergence regime
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The biotope is mainly subtidal, but also occurs at very low water so becomes exposed at very low water. A decrease in emergence is likely to be favourable and may allow the biotope to extend its distribution to previously intertidal areas.
Increase in water flow rate
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Sabellaria spinulosa appears to require suspended sand grains in order to form its tube so the biotope only occurs in turbid waters where sand is placed into suspension by water movement (Holt et al., 1998). Rees & Dale (1993) describe the typical habitat of Sabellaria spinulosa as occurring in moderate to strong tidal flow (see glossary). However, the relative importance of tidal versus wave induced movements in unclear. This biotope occurs in weak to very weak tidal streams but since Sabellaria spinulosa is often found in stronger water currents it is likely to be relatively tolerant of an increase. Increased water movement also favours filter feeding faunal groups so the richness of sponges and ascidians may increase. Therefore, the biotope as a whole is likely to be relatively tolerant of an increase in water flow rates.
Decrease in water flow rate
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Sabellaria spinulosa requires suspended sand grains in order to form its tube so the biotope only occurs in turbid waters where sand is placed into suspension by water movement (Holt et al., 1998). Rees & Dale (1993) describe the typical habitat of Sabellaria spinulosa as occurring in moderate to strong tidal flow (see glossary). This biotope occurs in weak to very weak tidal streams so a decrease in water flow rates would probably result in a reduction in abundance of Sabellaria spinulosa because reductions in water flow rate may reduce the amount of suspended sand grains available. This may limit growth of the worms or reduce the density of worms that can be supported in a particular area. In very slow water flow rates Laminaria hyperborea may be replaced by another kelp species although this is not likely to affected the overall nature of the biotope. The associated algal flora and suspension feeding faunal populations change significantly with different water flow regimes. Since the population of Sabellaria spinulosa may be reduced by a decrease in water flow rate intolerance is set to intermediate. Recovery should be high - see additional information below.
Increase in temperature
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The geographical distribution of many of the characterizing species in the biotope extends south of the British Isles. Long term slight increase or decrease in temperature is likely to have little effect on British populations of Sabellaria spinulosa as global distribution extends further south to the Mediterranean Sea. Laminaria hyperborea is stenothermal, and sporophytes are reported to tolerate an upper temperature of 15 -20 °C, and that the lethal limit would be between 1-2 °C above this normal temperature tolerance. Many species of red algae, such as Delesseria sanguinea and Palmaria palmata, are not tolerant of acute increases in temperature which is likely to result in impaired growth or death. Temperature increase may affect growth, recruitment or interfere with the reproductive cycle in some species, e.g. temperatures below 13 °C are required for new blade growth required in Delesseria sanguinea. Thus, it appears that a long term increase of 2 °C in temperature could result in the loss of some key species in the biotope and so intolerance is reported to be intermediate. Recovery should be high - see additional information below for rationale.
Decrease in temperature
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The geographical distribution of many of the characterizing species in the biotope extends north of the British Isles and many species are especially found in cooler waters. Sabellaria spinulosa is reported to be intermediately intolerant of temperature changes. However, Sabellaria spinulosa was not affected by the cold winter of 1963 (Crisp (ed.), 1964) so the species is tolerant of decreases in temperature. Birkett et al. (1998) suggest that kelps are stenothermal (intolerant of temperature change) and that upper and lower lethal limits for kelp would be between 1-2 °C above or below the normal temperature tolerances. Laminaria hyperborea sporophytes are reported to tolerate lower temperatures of 0 -19 °C (depending on season). Given its distribution in the North Atlantic this species is likely to be tolerant of a decrease in temperature. Temperature increase may affect growth, recruitment or interfere with the reproductive cycle in some species, e.g. temperatures below 13 °C are required for new blade growth required in Delesseria sanguinea. The biotope is therefore, likely to be tolerant of decreases in temperature and so intolerance is set to low. It should only take a short time for species growth rates to return to normal following periods of low temperature and so a rank of very high is reported.
Increase in turbidity
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High turbidity reduces incident light for photosynthesis. The kelps should not be significantly affected for the period of increased turbidity at the benchmark level. A small reduction in photosynthesis and growth may occur however. The red algae present in the biotope, such as Delesseria sanguinea are adapted to low light conditions so an increase in turbidity is unlikely to be fatal in the short term but in the long term will result in lower growth rates or a reduction in depth to which they occur rather than loss of all algae in the biotope. Intolerance is reported to be low. Recovery will be very high as normal photosynthetic rates return as previous turbidity conditions resume.
Decrease in turbidity
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The increase in light availability resulting from a decrease in turbidity will only affect the algae in the biotope probably increasing growth rates and the depth to which many species can occur. An increase in algal growth may have a smothering effect on some understorey species although at the level of the benchmark this is not likely to be significant. The other species in the biotope are likely to be not sensitive to changes in light attenuation resulting from turbidity changes.
Increase in wave exposure
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The key structural species, Sabellaria spinulosa, requires sufficient water movement to suspend sand particles into suspension for tube building and so is found in quite wave exposed areas. However, where the species exists as crusts, death may occur through break up by wave action and so increased exposure will result in potentially shorter colony life. Therefore, it seems that Sabellaria spinulosa crusts may be more intolerant of an increase in wave exposure than individuals. Increased wave exposure is also likely to remove older kelp plants, especially from the upper limit of their range. Intolerance of the biotope is set to intermediate. See additional information below for rationale.
Decrease in wave exposure
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The key structural species, Sabellaria spinulosa, inhabits a wide range of wave exposures (from sheltered to very exposed). However, decreases in wave exposure, where tidal streams are weak, may reduce the amount of available sand grains suspended in the water column, potentially limiting growth of the tube worms and restricting abundance and hence reducing the size of crusts. Decreased wave exposure is not likely to significantly affect Laminaria hyperborea plants, but may result in the loss of foliose red algae and an increase in abundance of filamentous red algae. In very sheltered situations Laminaria hyperborea is replaced by Saccharina latissima although this is unlikely to significantly affect the overall nature of the biotope. However, because a decrease in wave exposure may reduce the abundance of Sabellaria spinulosa intolerance of the biotope is set to intermediate. Recovery is likely to be high - see additional information below.
Noise
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The key structural species, Sabellaria spinulosa and the other characterizing species in the biotope, predominantly algae and sessile filter feeders, are not considered sensitive to noise disturbance. It is possible that predator avoidance behaviour in Ophiothrix fragilis may be triggered by noise vibrations although this has not been recorded.
Visual Presence
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The key structural species, Sabellaria spinulosa and the other characterizing species in the biotope, predominantly algae and sessile filter feeders, are not considered sensitive to visual disturbance.
Abrasion & physical disturbance
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Thin crusts of Sabellaria spinulosa seem to be moderately fragile and are quite easily broken up by storms or physical impacts and there is much evidence that reefs can be very badly damaged by fishing gear (Holt et al., 1998). Thus, abrasion at the level of the benchmark, is likely to cause damage to or loss of some of the Sabellaria spinulosa crust and loss of some of the organisms that live in or on it. Recovery is likely to high - see additional information below for rationale.
Displacement
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The key structural species (Sabellaria spinulosa) and the algal species are permanently attached to the substratum and would be destroyed by displacement resulting in loss of the biotope. Intolerance is therefore, set to high. However, displacement may not affect some of the species that may live in the biotope (e.g. Urticina felina, Ophiothrix fragilis), The biotope may also contain other permanently attached species (e.g. Halichondria panicea) which are likely to be highly intolerant of displacement. Mobile species in the biotope are unlikely to be affected. With the total loss of the key structuring species recovery of the biotope can take a long time and a rank of moderate is recorded - see additional information below for rationale.

Chemical Factors

Synthetic compound contamination
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Sabellaria spinulosa seems to be very tolerant of pollution by synthetic chemicals (Holt et al., 1998). The species was found closer to the acidified halogenated effluent discharge polluting Amlwch Bay in North Wales than any other organism, and was found in larger numbers at intermediate distances away (Hoare & Hiscock, 1974). Adult Laminaria hyperborea was one of the most tolerant algae at Amlwch although the richness of epifauna/flora decreased near the source of the effluent and red algae were absent from Laminaria hyperborea stipes within Amlwch Bay. Holt et al. (1995) state that mature Laminaria hyperborea may be relatively tolerant of chemical pollution probably due to the presence of alginates. Holt et al. (1995) suggested that Delesseria sanguinea is probably generally sensitive of chemical contamination although other red algae may be less sensitive. The sea anemone Urticina felina also survived in Amlwch Bay (Hoare & Hiscock, 1974). However, although many of the key species appear to be tolerant of chemicals many other organisms in the biotope are likely to be highly intolerant and increases in contaminants would probably result in reduced species diversity. However, overall, most species in the biotope are likely to be largely unaffected and an intolerance rank of low is reported. It is also possible that, because the key structuring species, Sabellaria spinulosa, is so tolerant of polluted conditions, the biotope may replace others where pollution is high. Recovery from sublethal effects is likely to be rapid.
Heavy metal contamination
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The key structural species in the biotope, Sabellaria spinulosa, was recorded from polluted waters in the northeast of England with higher levels of zinc, lead and copper than normally found in coastal waters (Jones, 1972). Laminaria hyperborea was also present at polluted sites, though with lower growth rates, as well as the anemone Urticina felina. However, some of the other species in the biotope such as Echinus esculentus, which were absent from or occurred only rarely in polluted sites (Jones, 1972), are more intolerant of heavy metals. Therefore, the biotope would appear to tolerate increased levels of heavy metal pollution and may actually replace other more intolerant biotopes although species diversity is likely to suffer as pollution increases. Recovery is likely to be high - see additional information below for rationale.
Hydrocarbon contamination
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It is not known how the key structural species in this biotope, Sabellaria spinulosa, reacts to hydrocarbon contamination. Kelps, such as Laminaria hyperborea, have a mucilaginous slime layer coating that 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). Echinoderms such as Ophiothrix fragilis and Echinus esculentus which may be found in this biotope are generally considered to be very intolerant of marine pollution. Laboratory experiments have shown Ophiothrix fragilis to be intolerant of hydrocarbon pollution (Newton & McKenzie, 1995). However, in the absence of information regarding Sabellaria spinulosa it is not possible to assess the intolerance of the biotope.
Radionuclide contamination
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Insufficient information.
Changes in nutrient levels
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Sabellaria spinulosa has been observed to be abundant at sites close to sewage discharge (Walker & Rees, 1980) and so is probably tolerant of changes in nutrient levels. The species was also abundant at sites in the northeast of Britain affected by high levels of nutrient and sewage pollution and high turbidity. Other species, such as Laminaria hyperborea and the red algae Delesseria sanguinea and Lithophyllum incrustans, are also tolerant of changes in nutrient levels although growth rates may fall if nutrient levels decline drastically. Nevertheless, the biotope appears to be tolerant of changes in concentration of nutrients. There may be some species in the biotope, however, that are intolerant of the direct or indirect effects of increased nutrient levels resulting in a decline in species diversity.
Increase in salinity
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The biotope is not found in areas of high salinity, such as rock pools or hypersaline lagoons. A long term increase in salinity is likely to result in the loss of the biotope so intolerance is reported to be high. Recovery from total loss can take many years and a rank of moderate is reported - see additional information below.
Decrease in salinity
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Although Holt et al. (1998) suggest that Sabellaria spinulosa does not seem to penetrate into low salinity areas, dense populations do occur in the Solway Firth and Bristol Channel, both areas at the entrance to estuaries. The other important characterizing species in the biotope are tolerant of some change in salinity. Delesseria sanguinea, for example, occurs in salinities as low as 11 psu in the North Sea. However, Laminaria hyperborea grows optimally between 20 -35 psu and may be lost at lower salinities. However, some species in the biotope such as the sea urchin Echinus esculentus are unlikely to survive in lower salinity and may perish. Most characteristic species are likely to survive a decrease in salinity so intolerance is set to low.
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. No information could be found regarding the tolerance of the key structural species, Sabellaria spinulosa, to decreases in oxygenation although the species is reported to be generally quite tolerant of changes in water quality (Holt et al., 1998). The algae in the biotope produce oxygen during photosynthesis so may be tolerant although Kinne (1972) reports that reduced oxygen concentrations inhibit both photosynthesis and respiration. Many of the other species in the biotope (e.g. Halichondria panicea, Botryllus schlosseri and Urticina felina) are recorded as having intermediate intolerance to deoxygenation (see individual species reviews). In the infralittoral the biotope becomes exposed to air at extreme low water so the effects of low concentrations in the water column for a week may be reduced. No species are expected to be lost in great numbers by the benchmark decrease so intolerance of the biotope is reported to be low. Deoxygenated conditions are unlikely in the infralittoral zone of moderately exposed coasts. Recovery will be very high as metabolic processes return to normal.

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 but is unlikely to result in loss of the biotope. There are no known microbial pathogens affecting the biotope so intolerance is reported to be low.
Introduction of non-native species
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There are no known non-native species likely to significantly displace or affect native species in the biotope (Eno et al., 1997). However, several non-native species have become established in British waters so there is always the potential for this to occur.
Extraction
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Sabellaria spinulosa is unlikely to be harvested because it has no commercial value. However in Morecambe Bay, fisheries for the pink shrimp Pandalus montagui have been implicated in the loss of subtidal Sabellaria spinulosa reefs (Taylor & Parker, 1993). Species diversity will probably decline greatly as many organisms live attached to the Sabellaria spinulosa crust. Laminaria hyperborea is harvested commercially Scotland and Ireland. However, kelps are probably not present in high enough density in the MIR.SabKR biotope for harvesting to take place. Echinus esculentus is also collected commercially but again, not in numbers that would adversely affect the biotope. Furthermore, Nichols (1981) pointed out that most divers missed small specimens within kelp beds. It is possible that if the marine aquarium trade continues to develop, species such as Urticina felina may be targeted.

Overall, a high intolerance has been suggested following the evidence of Taylor & Parker, 1993. Recovery should be moderate (see additional information).

Additional information icon Additional information

Recoverability
Recolonization by component species is likely to be high because many of the key or characterizing species have frequent recruitment and rapid growth rates. Sabellaria spinulosa has a long lived larva with widespread dispersive ability and can recruit readily particularly to areas where live adult or tubes are present. Sabellaria spinulosa seems in many cases to acts as a fast growing annual and early colonizer, but on more stable reefs the animals seem to be able to live for a few years. Areas where Sabellaria spinulosa had been lost due to winter storms appeared to recolonize quickly up to the maximum observed crust thickness (2.4cm) during the following summer (R. Holt pers. comm. cited in Holt et al., 1998). Recruitment of Sabellaria spinulosa can be affected by environmental conditions and so is often highly variable. The kelp plants are also likely to recover fairly rapidly. In areas cleared of Laminaria hyperborea plants for example, abundance has been seen to return to pre-harvesting levels after 1-2 years although plants were smaller (Sivertsen, 1991 cited in Birkett et al. 1998). Experimental clearance experiments in the Isle of Man (Kain 1975; Kain, 1979) showed that Laminaria hyperborea returned to near control levels of biomass within 3 years at 0.8 m. Recovery of many other species in the biotope is also rapid. The sponge Halichondria panicea for example, is fast growing and can rapidly recolonize bare rock. However, there are some species in the biotope, such as Urticina felina, that take longer to return due to poor dispersal (Solé-Cava et al., 1994) and slow growth (Chia & Spaulding, 1972). Encrusting coralline algae such as Lithophyllum incrustans are also very slow growing and may take many years to recover original percentage cover. Thus, although the biotope will probably recover within five years a return to full species richness and abundance may take many more years. Holt et al. (1998) suggest that recovery of Sabellaria spinulosa after widespread loss does not appear to be very good and so recovery from a factor that completely removes Sabellaria spinulosa has been assessed as moderate. Recovery from wide scale loss seems to be poor even after cessation of fishing (Holt et al., 1998) and in many areas Sabellaria spinulosa has become replaced by Mytilus edulis and sand dwelling amphipods (Jones et al., 2000). Thus, if live Sabellaria spinulosa or tubes remain recovery is likely to be high but if whole populations and the tubes are lost recovery will probably take much longer, if at all, and so in these instances is reported to be moderate.

This review can be cited as follows:

Hill, J.M. 2001. Sabellaria spinulosa with kelp and red seaweeds on sand-influenced infralittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/08/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=144&code=1997>