The abundance of the common intertidal barnacles, Chthamalus montagui, Chthamalus stellatus, Semibalanus balanoides and Elminius modestus has been monitored since 1951 at a site near Cellar Beach, River Yealm, south Devon. Counts are made at 12 levels on a transect between high tide and low tide. The two chthamalids are of warm-water distribution while S. balanoides is a boreo-arctic species; changes in the abundance of these species are linked to environmental temperature. Maximum fluctuations occur in the lowermost third of the intertidal zone. The proportion of Chthamalus adults is correlated with annual mean inshore sea temperature two years earlier, while the proportion of S. balanoides adults is negatively so correlated. This relationship accounts for over 40% of the variance. A smaller part of the variance (<20%) is explained by intensity of larval settlement, also related to climate. The fourth barnacle, E. modestus, is an Australasian immigrant that arrived in England during World War II and reached south Devon in 1948. It increased during the 1950s on the transect but has since stabilized at a low level of abundance that shows large interannual variations not directly related to temperature. Between 1951 and 1975, coinciding with a secular decline in sea temperature, there was a long-term trend towards reduction of Chthamalus and increase in S. balanoides; this trend has reversed since. Removal of the long-term trend reveals a short-term fluctuation of approximately 10-y frequency that correlates with a cycle in sea temperature two years earlier. These cycles are close to the 10–11 y solar (sunspot) cycle between 1951 and 1975.

In order to investigate the characteristic species and the relative importance of selected environmental conditions of rocky bottom communities in coastal waters and to estimate their richness, 27 sites in the Brest area were surveyed by diving. The abundances of underwater species, from a check-list of 115, were plotted as number of individuals or colonies in m2 or in percentage cover of the rock, against the environmental conditions (depth, bedrock slope, substrate type and sediment nature of the nearest soft bottom). Raw data were converted to biovolume expressed as mm3 m–2 and expressed as log 10 (x + 1).

Various correspondence analyses were applied to these data: the first included bedrock slope (lit/dark surfaces) and takes into account the four biological formations according to the depth. It shows zonation with depth and decreasing light as factor 1, hydrodynamic conditions (waves or current) as factor 2, mixing of estuarine and oceanic waters as factor 3 and turbidity as factor 4. Four species assemblages emerge from these four axes, for which the main species contributing to the four axes may be considered as characteristic species. These correspond well to four broad communities described in British waters: very exposed to wave-action, semi-exposed to wave-action, exposed to strong tidal current, very sheltered sites. The second analysis, in which lit and dark surfaces are distinguished, but some very close sites are fused together, shows in detail the photophilous or sciaphilous nature of the species. Values of hydrodynamic conditions and percentage of surface light plotted on the 'stations-points' of the graphs allow drawing of a factorial network which may be used as hydrodynamic and illumination scales.

Activity of Patella vulgata was monitored in the asymmetrical tidal regime of an Irish sealough, Lough Hyne, and also outside the lough in a normal tidal regime. An automated method was used, allowing continuous records to be made over two weeks. Most activity occurred at night while the limpets were emersed. Rainfall depressed activity. There was little activity during daytime emersion, contrary to the results of previous studies in which low-shore limpets foraged diurnally as well as nocturnally. Timing of activity in relation to tidal coverage was similar inside the lough and outside.

Activity of high-shore limpets within the lough was greater at spring tides than at neaps, but that of low-shore limpets was greater at neaps. Outside the lough, both high-shore and low-shore limpets showed greater activity at spring tides. Reasons for the differences are discussed.

Using Maximum Entropy Spectral Analysis, three periodicities underlying limpet activity were indicated. These were at h, 124 h and 8–2 h. When limpet activity was simulated by adding three sine waves of appropriate periodicity, rhythms very similar to those recorded from the shore were produced.

Gelidium pristoides dominates the lower and mid-eulittoral zones of rocky shores in the eastern Cape, South Africa. A disproportionately high percentage of the plants is attached to barnacle and limpet shells, or restricted to rock crevices. Our experiments at Port Alfred indicate that this distribution is caused by grazing by the limpet Patella oculus and/or strength of attachment of the plants to the different substrata. Exclusion of limpets caused an approximately four-fold increase in the cover of G. pristoides on rock, and an increase from almost 0 to 80% cover on sterilised (dead) limpet shells. Measurements showed G. pristoides to be more than 50% more strongly attached to barnacle and limpet shells than to rock. The distribution of G. pristoides on the various substrata is largely determined by limpet grazing and possibly the different strengths of attachment to the different substrata. The upper distribution limit of G. pristoides is set by physical effects of emersion and was largely unaffected by limpet exclusion. Competition with other algae is important in setting the lower limit: in the sublittoral fringe, although limpet exclusion enhanced recruitment, juveniles were later displaced by articulated corallines, and adult transplants senesced because of encrusting coralline epiphytes.

A massive toxic bloom ofChrysochromulina polylepis occurred along the Swedish west coast in May and June 1988 with severe effects on most biota in shallow marine habitats. In the present study, the effects on the common dog-whelk,Nucella lapillus was investigated in the archipelago at the mouth of the Gullmar Fjord.

Mortality varied throughout the archipelago, with extinction of populations in the inner parts and survivors found only on the outermost islands. Even on these sites, mortality could be as high as 98­99%. Extensive samples of survivors and dead animals were divided into five age groups dependent on size and wear of the shell. The cohort consisting of 3­4 year old individuals suffered the lowest mortality, while mortality was almost total in younger and older cohorts. In each age group, except the oldest, survivors were significantly larger than the dead.

The number of egg capsules laid per female in 1988 seemed normal, but about half of the capsules were empty. The number of young per capsule was significantly lower in 1988 compared to 1989, but the young were significantly bigger.

Seasonal changes in the assemblage structure of dominant epipelic diatoms were studied along a transect crossing a salt marsh, sandflat, and mudflat of an estuarine intertidal shore at Berrow Flats, Somerset, UK. Seasonal changes in cell numbers displayed different patterns in the salt marsh and sandflat/mudflat. At salt marsh sites highest numbers of individuals were recorded in summer followed by a smaller autumn growth, while in the sandflat lower numbers showed no seasonal pattern. Repeated annual patterns in the succession of taxa were not observed as environmental conditions changed at the study site with time. Measurements of salinity, pH, interstitial water content, air and soil temperature were taken together with the diatom samples. A canonical correspondence analysis was employed to relate seasonal changes in assemblage structure to measured environmental variables. Total percentage variation in the first four axes of the species/site-environmental biplots ranged between 54 and 66°. In winter, sites and species separated most significantly along gradients of salinity and levels of organic matter. In spring and autumn, interstitial water content became a more significant environmental variable. By summer steep gradients in pH, levels of organic matter, and hypersaline conditions separated sites and assemblages into more discrete groups when compared to the more even spread of points in the other seasons. The results indicate that different combinations of environmental variables influence diatom assemblage structure seasonally.

Strombidinopsis species were collected from theGulf of Alaska, Gulf of Mexico, Caribbean Sea, Gulf of Maine, and Barents Sea. Six strains were conservatively placed in six species: Strombidinopsis chilorhax sp. nov.; Strombidinopsis batos sp. nov.; Strombidinopsis sphaira sp. nov.;Strombidinopsis cercionis sp. nov.;Strombidinopsis acuminatum Fauré-Fremiet, 1924; and Strombidinopsis spiniferum (Leegaard, 1915) comb. nov. Based on the characters of these species, the diagnosis of the genus Strombidinopsis was revised.

Two new Appendicularians: Inopinata inflata gen. nov., sp. nov. and Mesopelagicn caudaornata gen. nov., sp. nov., from the family Oikopleuridae (Lohmann 1915), subfamily Oikopleurinae (Lohmann 1896a), are described from specimens collected at mesopelagic depths (660–840 m) in Bahamian waters by the ‘Johnson-Sea-Link’ manned submersibles.

The hypobranchial gland ofMorula gramilata (Duclos) has been morphologically and histochemically characterized. The marginal zones of the gland have mucocytes and eosinophil cells while the median region has in addition ciliated cells and gland cells. Neurosensory cells are also present. Two types of mucous cells have been identified. Type I secrete a diastase-resistant, neutral mucopolysaccharide, while type II secrete PAS unreactive, strongly acidic and highly sulphated mucins. Exposure to low temperatures, ultraviolet rays and irritants resulted in the production of a purple dye.

Changes in dietary lipids were investigated in laboratory feeding experiments simulating herbivorous and coprophagous modes of feeding in the bivalve mollusc Scrobicularia plana (da Costa). The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory experiments while faeces from the crustaceanNeomysis integer (Leach) feeding on Scrippsiella were used as the food in coprophagy experiments. Changes in dietary total fatty acids, sterols and fatty alcohols were characterised by analyses of the food, faeces andanimal tissues using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

There is a net decrease in the total lipid of the digested material during both herbivory and coprophagy. However, while fatty acids are assimilated, sterols are contributed to the faeces, leading to a decrease in the fatty acid:sterol (FAST) ratio of the digested material. Coprophagy decreases the ratio still further, such that faeces have a FAST ratio of <1

Scrobicularia preferentially assimilates dietary polyunsaturated fatty acids (PUFAs). Reworking of sedimentary material (as in coprophagy) will lead to PUFA-deficient sedimentary fatty acid distributions. Both herbivory and coprophagy lead to relative increases in 'bacterial' odd carbon-number normal and branched fatty acids in the digested material, though not the 'bacterial' marker 18:1 Benthic molluscan feeding, particularly coprophagy, contributes partly to the 'bacterial' fatty acid content of the sediments.

Scrobicularia contributes its own sterols to the faeces, especially cholesterol. Such contributions aredependent on the dietary sterols present. With a cholesterol-poor diet (herbivory), A5 4–desmethyl sterols are contributed to the faeces and dietary A8(14) sterols decrease, suggesting a A8(14) U021e2; A5 conversion may occur. With a cholesterol-rich diet (coprophagy), the A5 sterol is taken up from the diet.

This paper describes a novel sexually dimorphic pattern of behaviour in the tube-building amphiplodAmpelisca abdita (Mills). Mature males and females enter the water column at night. However, while males enter the water column every night, females enter it only when they moult. Since female amphipods only mate shortly after they moult, it is hypothesized that this sexually dimorphic pattern of free-swimming behaviour is an adaptation that permits males and receptive females to locale each other during the brief period when copulation can occur, while reducing the time that females are exposed to pelagic predators.

The influence of photoperiodicity on hatching of Sepia officinalis was investigated under different experimental light-dark (LD) conditions. The results are viewed in relation to some relevant properties of the perivitelline fluid (PVF) and the egg capsule during embryonic development. In embryos of S. officinalis the transition from light to dark ap-pears to act as a 'Zeitgeber' or synchronizer. The embryos consistently hatched during periods of darkness, even when the duration of the dark period was short (1–4 h) and replaced part of the natural light period. The hatching rhythm was independent of the embryonic stage at which the experimentwas started. Embryos that developed under a given LD rhythm did not hatch at that rhythm if it was changed or eliminated. In the absence of an external LD rhythm the time to hatching increased. Lack of pigmentation in the egg envelope appeared to reduce the time to hatching. If embryos were exposed to a single dark period of 1–4 h significantly more hatched during darkness while a dark-pulse of ten minutes resulted in no hatching. At the end of embryonic development the egg capsule of S. officinalis becomes thinner due to the expanding PVF. Absence ofthe envelope did not affect embryonic development but dramatically increased mortality and prema hire hatching (96%). Spectrophotometrical investigations indicated that light between 200 and 900 nm is absorbed similarly by the envelope and by female ink. The function of pigmentation in the envelopes remains obscure.

The aims of this study were to ascertain if individual turbot females show a seasonal decline in their egg-size when kept in conditions of constant temperature, and to relate turbot egg-size to the length and yolk-sac index of the emergent larva. Each female showed a significant seasonal egg-size decline and there was a positive correlation between egg-size and the length and yolk-sac index of the subsequent larva. However, larval length was not related to yolk-sac index, nor was the ratio of yolk-sac index: larval length related to egg-size. The maximum mean egg-size tended to increase with the female's weight and length. The implications of these findings are discussed in terms of the general ecology of turbot and its culture.

A total of 113 broods of Ostrea edulis L. larvae from a closely-controlled hatchery conditioning regime, from specific broodstock treatments, and from brooding oysters taken from a wild population in Poole Harbour, was analysed for fatty acid composition. Major differences in polyunsaturated fatty acids (PUFAs) were detected as the year proceeded, with increased levels of 20:5 (n-3) and 22:6 (n-3) from late June. Significant decreases in the PUFA content of both phospholipids and neutral lipids accompanied development from fertilized eggs to immediately pre-liberation larvae, but there was some evidence that the 20:4 (n-6) and 22:6 (n-3) content of phospholipids was protected. Fatty acid composition and content of newly liberated larvae were influenced by conditions during broodstock fattening and early gametogenesis (phospholipids) and by conditions during the later stages of oocyte development (neutral lipids).