Clones of Ditylum brightwellii and Thalassiosira nordenskioldii were isolated from New York coastal waters, and PCB-resistance in D. brightwellii was induced in the laboratory by exposure to increasing concentrations of PCB. Resistance could not be similarly induced in T. nordenskioldii, but was serendipitously discovered in unexposed cultures that had undergone sexual reproduction.

Cells of the resistant strain were substantially larger than those of the sensitive strain in both species. Larger vacuole space seemed to account for this in D. brightwellii, but in T. nordenskioldii larger cells contained more carbon. Experiments with14C-PCB tracer indicated that PCB accumulation was less in resistant strains of both species. Neutral lipid content per cell, as determined using the fluorophore Nile Red, was similar for resistant and sensitive strains of both species. Sub-cellular examination of lipid droplets in D. brightwellii suggested that the PCB-resistant strain may be sequestering this lipophilic toxicant in a location removed from physiological activity. In T. nordenskioldii a decreased ratio of neutral lipidxarbon may reduce intracellular accumulation of PCB. These diatom species have developed PCB resistance in the highly PCB-polluted Hudson River estuary and, since they are the preferred food of dominant copepods, they may offer less PCB per unit ration to zooplankton grazers.

The characters widely used for identifying members of the Ampelisca diadema group of species (A. diadema, A. spinipes, A. tenuicornis and A. armoricana) are reassessed. Highly variable characters are discarded in favour of more stable ones. Both sexes of all four species known from the north-east Atlantic are figured and diagnoses and a key to the species are provided.

An intensive investigation of the benthic biology of the Porcupine Seabight, to the south-west of Ireland, was carried out by biologists from the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL) between 1977 and 1986. More than 400 benthic samples were obtained during the study using towed gears and corersover the depth range 200 to 4500 m. Transect and time-lapse photography was used extensively. This paper summarises the techniques employed and provides an analysis of the depth and seasonal coverage. In addition a review is provided of available data on the physical, chemical and geological characteristics of the Porcupine Seabight area, including information collected during the IOSDL study. Finally, existing publications based on the study are listed.

A study was made ofGeryon trispinosus (Herbst) from the Porcupine Seabight in the north-east Atlantic, based on detailed examination of 687 specimens, and carapace length data for a further 2000. Evidence indicates that males become sexually mature at 30–35 mm carapace length, and females between 12 and 15 mm. There is probably a terminal anecdysis, in males at 55–65 mm and in females at 45–50 mm. The chelae show limited heterochely and marked right-handedness in both sexes. Relative growth in chelae and abdomen followed expected patterns, except that the right chelae of males decreased in relative size at the puberty moult. Seasonal reproduction is indicated: laying in September/October, hatching the following May, and settlement from the plankton in August/September.

The demersal ichthyofauna of the continental slope of the Porcupine Seabight, eastern North Atlantic, was studied from 144 samples taken by three different types of otter trawl. At least 118 species from 43 families were represented among some 54,000 specimens collected from 247 to 2172m soundings. Collectively, the catches were dominated in species richness by the Macrouridae, Alepocephalidae and Squalidae and in abundance by the Synaphobranchidae, Macrouridae and Moridae. Separately, relative abundance of species was more similar between the two larger trawls, setting their catches apart from the smaller net. Gear selectivity evidently accounted for this variation, which was examined by an index we developed and call species fidelity. This accounts for patterns of continuous faunal change with increased soundings concomitant with variance in species adult size and mobility. In pursuance of a more accurate representation of relative biomass and abun-dance than achieved hitherto, the best estimate, within the limitations imposed by the sampling gears and regime, was derived from a combination of the mean values per 200m stratum of the two large trawls with the addition of those of the eel, Synaphobranchus kaupi, from the small gear. Tentative comparisons between these results and those from elsewhere suggest that the Porcupine Seabight is generally lower in biomass and similar or lower in abundance. It was concluded that an accurate indication of ichthyofaunal structure with increased soundings can only be achieved through a detailed knowledge of the size structure of each species over its entire sounding range synthesized from a multi-trawl investigation via analyses of species fidelity.

The dynamics of clearance, segregation and elimination of a marine bacterium, Moraxella sp., by the shore crab, Carcinus maenas (L.) has been studied utilizing fluorescent and radiolabelling techniques. In addition to the gills, the hepatopancreas was a major site of bacterial accumulation with sequestration occurring within haemocyte clumps and groups of stationary cells in this organ. The heart, excretory organ and subcuticular tissues also incorporated bacteria, but to a lesser extent. By the first day post-injection, many of the segregated micro-organisms had been removed from the organs. This latter process was not due to the exodus of laden haemocytes or of intact cell clumps from the host but seemed to result from lytic action by the host blood cells. Little material arising from such bacterial/haemocytic interaction was, however, immediately excreted, and much was relocated in the general body tissues as well as the gill nephrocytes.

The population biology of the crab Liocarcinus depurator was studied for one year in the mussel raft culture areas of the Ria de Arousa. The density and biomass of this species is much higher in the raft areas, especially in the outer part of the ria, than in the central channel area. Maximum abundance occurred during the winter months (up to 8-80 g wet weight m and 0-44 individuals m.

Maturity size in females was set at 28-30 mm carapace width, (based on ovigerous females) and is attained in the first year of life. The ovigerous females were most abundant in January (approximately 70% of the mature females), but another less important maximum value was observed in May, attributable to a second spawning. Modifications in the sex ratio from 1:1 affected individuals larger than the maturity size during the season when there was a greater number of ovigerous females present. Data on sex ratio and breeding cycle indicate that ovigerous females move towards the raft areas located in the outer part of the ria. Trawl recruitment took place in the stations located in the outer Ria, and mainly in August-September, although it continued to a lesser extent in autumn.

The Von Bertalanffy growth function was fitted to both sexes in the two outer stations. Growth rate was higher in males than in females, while variability between stations was less important. However the growth rate and reproductive output of L. depurator in the Ria de Arousa was higher than in populations from other geographical areas, possibly because of the availability of food from the rafts and or the oceanographic conditions in the ria.

The occurrence of a population of Ophelia bicornis has been recorded at a site which may be the most northerly for the species, and the only one within the United Kingdom. The irregular and patchy distribution of the population is described and reviewed in relation to other recorded occurrences of the polychaete.

Microbial films represent the site at which grazers exert their influence upon the recruitment of settling macroalgae and animals. The overall purpose of this study of seasonal and spatial variation in abundance and composition of epilithic microbial films was to relate such patterns to macrobenthic community dynamics within the Fucus-bar- nacle mosaic characteristic of moderately exposed rocky shores on the Isle of Man. Additionally selective grazing in Patella vulgata was examined by comparing dietary and epilithic microalgal assemblages and how this varied seasonally and spatially within the mosaic. Chlorophyll analysis was used as an index of microalgal standing crop while SEM allowed in situ estimation of microalgal abundance.

Development, growth, and survival data derived from laboratory experiments are provided for Lepeophtheirus salmonis, a common ectoparasite of wild and sea-farmed salmonids. The mean development time of eggs was 419·1 hours (17·5 days) at 5°C, 207·1 hours (8·6 days) at 10°C, and 130·8 hours (5·5 days) at 15°C. Development from the first nauplius to the infectious copepodid stage took 222·3 hours (9·3 days) at 5°C, 87·4 hours (3·6 days) at 10°C, and 44·8 (1·9 days) hours at 15°C. Development from the egg to the adult male took 40 days, and from the egg to the adult female 52 days at 10°C. No egg development occurred at 10‰ salinity. At 15‰ eggs developed but failed to produce active nauplii. At higher salinities (20–3‰) active nauplii were produced, but copepodids were only obtained at 30‰. Copepodids survived for less than 1 day in waters with a salinity of 10‰ or less. At higher salinities (15–30‰) and temperatures of 5,10, and 15°C average survival times ranged between 2 and 8 days.

Laboratory feeding experiments with the sea scallop Placopecten magellanicus were carried out to compare scope for growth (SFG) to measured growth and determine the effect of diet on carbon and nitrogen SFG. Diets consisting of cultured phytoplankton, kelp detritus, and resuspended sediment were provided daily for 52 days (October-December). Measurements of clearance rate, absorption efficiency, respiration, O/N ratio, and carbon and nitrogen content of diets and scallop tissue were used to construct carbon and nitrogenbudgets for each diet. Growth coefficients were calculated from change in tissue weight during the study period.

Ultrastructural, histological and histochemical studies were performed on the gonad of adult Pecten maximus at various intervals during the reproductive cycle in St Brieuc Bay, France, in order to understand better the sources and transfers of energy to developing gametes in scallops. In addition to the well-known pathways of energy acquisition through feeding and transfer of somatic reserves, a number of novel pathways were demonstrated. These were grouped into two categories: atretic recycling and intestinal loop transfer. Evidence is presented for the recovery of lytic material (resulting from gamete atresia) in the gonad acini, gonoducts, and integument; and the direct transfer of metabolites from the gonad intestinal loop to the developing gametes via vesicular cell-haemocyte couples, which appear to follow fibrous pathways within the loose connective tissue extending from the base of the intestinal epithelium to the acini. A schematic diagram summarizes the sources and transfer mechanisms of the energy exchanges involving the developing gametes in Pecten maximus.

Experiments involving three species of copepods(Acartia clausi Giesbrecht 1889, Pseudocalanus elongatus Boeck 1872 and Calanusfinmarchicus Gunnerus 1765) incubated with freshly produced copepod faecal material were conducted and analyzed using automatic image analysis. For two species (A. clausi and C. finmarchicus) the bulk of faecal material was not ingested but was fragmented. This process, coprorhexy, was accompanied by a shift toward smaller particles in the particle size-spectrum. Increases in total volume of the faecal particles after incubation with these copepods led us to propose a process which we refer to as 'coprochaly', derived from the Greek xot/Vaoio,(a loosening, as of bandages). Coprochaly was promoted by manipulation of the faecal material by the copepods. For the third species (P.elongatus) coprorhexy and coprochaly were coupled with coprophagy (ingestion of faecal material). Calculations indicated that the combined effect of coprorhexy and coprochaly reduced sinking velocities of the faecal particles by up to 50%. These processes increase pelagic residency time of particles, increase substrate area for aerobic microbes and presumably enhance remineralization of particulate organic matter.

Analysis of the total copper and zinc content of four species of talitrid amphipods, Orchestia gammarellus, O. mediterranea, Talitrus saltator and Talorchestia deshayesii throughout a complete spring/neap tidal cycle failed to reveal any significant effects of moulting upon body copper or zinc in any species. Moulting was synchronized to the lunar cycle only in T. saltator, taking place 5–7 days prior to a new moon. The fact that no significant changes in body metal concentrations took place with the moult cycle is discussed in relation to the use of talitrid amphipods in copper and zinc biomonitoring programmes.

Cholorophyll a, primary production and the patterns of 14C assimilation into the major end-products of photosynthesis were determined for phytoplankton in the coastal waters off Plymouth, in order to study their physiological ecology during spring conditions. At the end of the study period, a diatom bloom occurred after the development of a slight thermocline. Throughout the pre-bloom period, the majority of the label was found in storage products, and phytoplankton growth was not nutrient-limited. During the development of the bloom, however, an increase in protein synthesis was found, which is interpreted as a result of an active phytoplankton growth. Both synthesis ratios for protein to storage products, i.e. lipid and polysaccharide, (P/L+S) and protein to low molecular weight metabolites (P/M), summarize the variations in the physiological state of phytoplankton during this study. Comparison of the P/M synthesis ratio and different estimations of phytoplankton growth rate shows the usefulness of this index for characterising natural populations.