In February 1996, the oil tanker 'Sea Empress' spilt over 70 000 t of crude oil which contaminated ca 200 km of coastline (Milford Haven, Wales, UK). The effects of the oil on immunity in mussels Mytilus edulis were investigated in parallel with the measurement of hydrocarbon contamination in the tissues. Initially, severe immunosuppression occurred in oiled mussels, corresponding with very high polycyclic aromatic hydrocarbon (PAH) levels. The haemocytes of mussels from oiled sites showed significantly reduced superoxide generation and phagocytic activity, effects likely to have deleterious consequences for successful disease resistance. As contaminant levels decreased, the immunosuppression became less extreme and recovery was evident by May 1996. Between October 1996 and March 1997, immune activity in the haemocytes of the previously oiled mussels was again significantly reduced, coinciding with increased PAH levels. During this latter period, certain high molecular mass PAHs (characteristically derived from combustion processes) were primarily responsible for the increase, occurring at similar concentrations in the mussel tissues to those observed just after the spill. A subsequent reduction of hydrocarbons in June 1997 was followed by another, but less marked, increase in PAHs between October 1997 and March 1998, coupled with only minimal changes in immunity. The results show that immunosuppression following the oil spill was severe, but that recovery followed a few months later and the initial effects were not therefore permanent. The results also suggest that seasonal peaks in combustion-derived PAHs may occur in the region and that these would have been greatly exacerbated early in 1996 by oil released from the 'Sea Empress'. KEY WORDS: Mytilus · Immune defence · Haemocyte · Oil spill · Hydrocarbon contaminationResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 206: 155-170, 2000 These include the induction of biomarker enzymes in fish and molluscs (Sole et al. 1996, Woodin et al. 1997, Stagg et al. 1998, Kirby et al. 1999, abnormalities in fish embryos/larvae (Hose et al. 1996, Bue et al. 1998 and haematological changes in vertebrates (Duffy et al. 1994, Walton et al. 1997.Despite the considerable effects that crude oil contaminants can exert on the physiology of marine animals, information concerning impacts on the physiology of natural invertebrate populations is more limited, particularly with respect to their immune defences. Globally, marine invertebrates constitute an important economic resource, and factors influencing their ability to resist disease and hence maintain healthy populations are of considerable relevance. Invertebrate immune defences comprise cellular and humoral components, which are highly efficient in combating pathogens and parasites and share many facets with vertebrate immune defences (Ratcliffe et al. 1985, Engstrøm et al. 1993. Laboratory exposure to contaminants can significantly alter immunity in invertebrates fr...

The first known occurrence of a naturalized population of Manila clam (Tapes philippinarum) in UK waters is reported. Introduced into Poole Harbour for aquaculture in 1988; by 1994 local fishermen and wading birds began to exploit this northernmost naturalized population in Europe. The licensed fishery currently supports 31 local fishers, landing approximately 250 tn. of clams in 2002. The current distribution of the clam in Poole Harbour, the biology of this naturalized population and the ecological impact of its introduction and fishery, is described.

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Oogenesis is compared in two cheilostome bryozoans with contrasting reproductive strategies. from southern Britain: Chartella papyracea (Ellis & Solander) is a non–placental ovicellate brooder, whereas Bugula flabellata (Thompson in Gray) is a placental brooder. The ovarian cycles are similar, and each oocyte develops in tandem with a single nurse cell. Eggs of both species are telolecithal, However, those of B. flabellata are less than 20% the volume of those of the other species, and there are considerable differences in the ultra‐structure of oogenesis. In both cases, spermatogenesis has the typical bryozoan pattern. Precocious insemination of the oocyte occurs in both species.