Fishing

Aggregate Extraction

Water Quality

Chemical Contaminants

The sensitivity of S. spinulosa to man induced change was summarised in a recent report (Holt et al., 1997a). This section draws heavily on that report.

Berghahn & Vorberg (1993) have suggested that Sabellaria spinulosa in it’s absence is a good indicator of fishing intensity in the Wadden Sea. Subtidal S. spinulosa reefs are reported to have been lost due to physical damage in at least five areas of the north east Atlantic. In the Waddensee, Riesen & Reise (1982) reported that extensive subtidal S. spinulosa reefs were lost from the Lister Ley, island of Sylt, between 1924 and 1982; they reported that local shrimp fishermen claimed to have deliberately destroyed them with "heavy gear" as they were in the way of the shrimp trawling. Reise & Schubert (1987) reported similar losses from the Norderau area, and attributed them to similar causes. Shrimp trawling still occurs in these areas and the S. spinulosa have not reappeared, but have effectively been replaced by mussel Mytilus edulis communities and assemblages of sand dwelling amphipods (Reise & Schubert, 1987). The mussels are also exploited.

Dorjes (1992) reported complete loss by 1987 of almost two km2 of Sabellaria spinulosa reef in Jade Bay, North Sea, the distribution of which had been described by Schuster (1952, ref not seen), and suggested that this was probably as a result of fisheries activities.

In Morecambe Bay fisheries for pink shrimp Pandalus montagui have been implicated in the loss of subtidal Sabellaria spinulosa reefs in the approach channels to the Bay (Mistakidis, 1956; Taylor & Parker, 1993). EU LIFE funded surveys in appropriate areas during May 1998, using grabs, small beam trawls and anchor dredges, as well as interview with local divers, found no evidence of Sabellaria spinulosa, although there were numerous pink shrimp, and some subtidal S. alveolata were found adjacent to known intertidal reefs (Fletcher, pers. comm.).

Warren & Sheldon (1967), discussing the pink shrimp fishery of the Thames Estuary and the Wash, reported that "it has been the accepted practice among commercial fishermen to search with a small hand dredge for the polychaete worm Sabellaria spinulosa and then trawl for shrimp in areas where this was found." Warren (1973) reported "In recent years ross (Sabellaria spinulosa) has been found only in small clumps in the Wash where the bottom is predominantly sandy, particularly towards the offshore end of the fishery. No reefs of ross are known to exist."

Graham (1955) assumed that trawling would damage Sabellaria spinulosa reefs but did not back this up with any direct evidence. He also assumed that recovery would be rapid as the worms were ‘effectively annual’.

Rees & Dare (1993), using a four point numerical scale of assessment of "risk of extinctions through natural and anthropogenic factors" for a number of benthic species, considered that the risk for S. spinulosa from trawl/dredge effects was high, scoring the maximum 4.

Clearly it is certain that at least in the short term Sabellaria spinulosa reefs would suffer severe direct damage by extensive aggregate dredging activities, and that aggregate extraction is very likely to occur in areas where S. spinulosa is found, as expected from the distribution and habitat requirements of the species. This has been noticed in practice by English Nature and others (e.g. various licensed dredging areas, Gilliland pers. comm.; East Anglia, Attrill pers. comm.). The extent of important Sabellaria reef structures, and speed of recovery from this damage, are presently unknown. Compared to fishing impacts, gravel extraction is likely to be more limited in extent, more controlled, and less likely to continue for very long time periods, so that although direct damage would obviously be severe, recovery from adjacent undamaged areas seems more likely. The likelihood of damage due to sediment plumes in areas adjacent to gravel extraction is presently less clear, since there is no knowledge of the effects of differing particle sizes upon Sabellaria, for example, although it would be surprising if damage was other than very localised given the preference for somewhat turbid waters.

Sabellaria spinulosa appears to be generally tolerant of changes in water quality. Hoare & Hiscock (1974) investigated the distribution of marine organisms around the outfall from a bromide extraction plant in North Wales. The effluent had a pH of 4 and among other contaminants contained free halogens. Species richness and diversity was markedly reduced within 150 m of the outfall both intertidally and subtidally, with red algae, Antedon bifida and Helcion pellicidum being particularly sensitive. However, S. spinulosa was found closer to the outfall than any other organism, and was found in larger numbers at intermediate distances than further away. Hoare & Hiscock (1974) also reported that other workers had described S. spinulosa as a pollution indicator but unfortunately did not give relevant references.

Furthermore, in a report on surveys of Dublin Bay in relation to sewage discharge and dumping, Walker & Rees (1980) reported that "In the dumping area and in the south-east of the bay downtide of the dump site, where depths are greater, the faunas resembled the Nucula/Sabellaria [spinulosa] community of Caspers. As well as having pollution indicator species, this latter community generally had greater faunal densities and diversities than elsewhere in the bay (except low diversities at the dump sites in 1971). Apart from a possible effect of depth, this suggests that the dumping was having an enriching rather than a degrading effect, although the probable sediment change since 1874 may imply a change in community type".

S. spinulosa was relatively unaffected by an outfall containing free halogens (see 3. Water Quality, above).

The only other information found was the following work on oil dispersants. Larvae of Sabellaria spinulosa were killed after several weeks in a 1 ppm concentration of an oil dispersant (detergent BP1002) while larvae in uncontaminated control experiments all survived (Wilson, 1968a). A 2.5 ppm concentration killed the larvae within a day or two. Since the toxicity of detergents varies enormously and no other species were tested, it is not known whether this represents a strong sensitivity to such chemicals on the part of S. spinulosa or not. Further experiments using heavier concentrations suggested that detergent adsorbed onto the sand particles forming the tubes of S. spinulosa and caused the death of larvae settling onto them, but that the effects lasted only a few days (Wilson, 1968c). No studies on the effects of oil or oil and detergent mixes were found, nor on more modern detergents.

Overall S. spinulosa seems unlikely to show any special sensitivity to chemical contaminants.

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