Sphaerechinus granularis (Echinodermata: Echinidea) is involved in the erosion of ‘coralligène’ concretions in the Mediterranean. In shallow water (10 m), a high abundance of this species (>20 ind 25 m−2) is associated with small diameter individuals (56·7 ±7·7 mm). In deep clean waters (>40 m), the abundance is lower (<1 ind 25 m−2) and the mean diameter is higher (86·0±9·3 mm). Daily erosion of Corallinaceae by this species is related to the urchin diameter (r=0.87). Local variations in urchin abundance and diameter influence the amount of CaCO3 eroded annually. In shallow waters, the eroded CaCO3 mass reaches 210 g m−2 y−1 vs 16 g m−2 y−1 in coralligène concretions in deep clean waters. Sphaerechinus granularis is an important biological agent which substantially erodes the Mediterranean coralligène concretions.

Changes in four macrobenthic assemblages of the muddy-fine sand Abra alba community along the north-west French coast were compared using several numerical analyses (distogram, Eigen vector filtering, clustering and multi-dimensional scaling). The faunistic composition of these four assemblages continuously changed during the 1978–1992 period. These modifications are characterized by more or less rapid and abrupt successions of distinct groups of species, but the amplitude and the frequency of these changes are different between sites. Comparison of the results provided by different analyses also reveal that these four macrobenthic assemblages did not fluctuate in parallel, and that local conditions might play a key role on their temporal variations. However, it is shown that a major mesoscale climatic event, the alternation of mild and cold periods, probably also influenced the temporal variations of these four macrobenthic assemblages. Thus it is likely that there is a combination of both local and mesoscale events influencing these communities. In certain cases, changes in local conditions were the major source of variations. Sometimes the impact of the mesoscale conditions was more apparent, especially at the northern sites where the amplitude of the variations of temperature was greater.

Patterns of the distribution of intertidal fauna in relation to the diversity of habitats were studied in the UNESCO Man and Biosphere (MAB) reserve of the archipelago of Molene and Ouessant (west Brittany, France). A classification of environmental features was developed in order to determine species richness, abundance, biomass and trophic structure of the macrobenthic fauna in this intertidal area which covers 1120 ha. The four descriptors of the environment were: (1) substratum (rock, boulders, sediment, pebbles); (2) height on the shore, based on the macrophytic zones: Pelvetia canaliculata/Fucus spiralis; Fucus vesiculosus / Ascophyllum nodosum; Fucus serratus; and Himanthalia elongata/Zostera marina; (3) wave exposure (sheltered, semi-sheltered, exposed); (4) percentage of algal cover (<50%, >50%). Each type was defined by a four-figure number and matched to a map codification. A two-way analysis of variance (ANOVA) and a posteriori Newman-Keuls test (P=0.05) were applied to the series of species richness and biomass. Among the 308 species sampled, 40 represented 90% of the total biomass. Maximal number of species was reached in boulder fields in the Himanthalia zone, under exposed conditions and high algal cover. The lowest number of species was observed in pebble fields of the Pelvetia zone and in the sedimentary areas. Trophic structures were dominated by suspension feeders and herbivores at high levels on the shore and by carnivores at the lowest levels. High vegetation cover and wave-exposed conditions were shown to increase with increasing faunal diversity. Links between patterns of habitat distribution and faunal diversity and biomass in different spatial scales are discussed.

The impact of colonization by Sargassum muticum (Phaeophyta: Fucales) on the resident macroalgal assemblage in tidepools was investigated in northern Spain. Sargassum muticum was allowed to colonize and spread in some tidepools, and was periodically removed in others. Changes in the abundance of macrophytes were recorded at three sites over two years. The colonization by S. muticum and the subsequent changes induced on the native assemblage was extremely variable among sites. Where the invader colonized profusely, it induced changes in the macroalgal composition of tidepools. The leathery group of macrophytes was significantly affected and changes were also observed in the foliose group. It was suggested that S. muticum may take advantage of their perennial and opportunistic traits in the interaction with groups of algae with different survival strategies. However, the spatial patchiness of the colonization may mitigate the impact of the invasion at local and regional scales.

The species composition, abundance and vertical distribution of micronektonic cnidarians has been investigated in the upper 2800 m at Discovery Station 9969, located in the cold regime in the eastern Weddell Sea, Antarctica. In total 22 siphonophore and 20 medusan species were identified. Overall siphonophores were more abundant than medusae, but the latter usually contributed much more to the biovolume. On average, cnidarians contributed more than 50% to the total biovolume of each catch; and they contributed >70% to the combined total of all the samples. Despite the high water content of these animals, these large biovolumes meant that the cnidarians formed ∼25% of the total carbon in each catch. The possible impact of these gelatinous cnidarian populations on the ecosystem is discussed.

The Arctic abyssal anemone Bathyphellia margaritacea, type species of the genus and of the family Bathyphelliidae is redescribed. Acontia in this species are highly variable both in quantity and in cnidome characteristics, implying that this genus is one of the links between acontiate and nonacontiate mesomyarian actiniarians, and has to be considered a ‘late’ mesomyarian according to the scheme proposed by Schmidt (1972b, 1974). By contrast, the new abyssal species Daontesia porcupina has normally developed acontia, a cuticle consisting of multistratified sheets and a more archaic and diverse cnidome, suggesting its systematic allocation within the ‘early’ mesomyarians. The allocation of the genus Daontesia to the family Bathyphelliidae is questionable.

Scanning electron microscopy was used to study the microstructure and internal growth lines of the temperate ahermatypic coral Caryophyllia smithi (Cnidaria: Anthozoa). The arrangement of internal growth lines in combination with the orientation of aragonite crystals were used to describe the pattern of skeletal development in C. smithi. The observed pattern was verified using observations from another study on skeletal development in C. smithi, but which was based only on external observations of skeletons of living and dead specimens in different stages of development. The pattern of skeletal development in C. smithi is suggested to be subdivided into three stages, based on the deposition of specific skeletal elements during the development of the skeleton. In the first ‘juvenile’ stage, various primary skeletal elements are formed: the basal plate, the septa and a primary and secondary septotheca. The second ‘half full grown’ stage is characterized by development of apparently only an extended basal attachment, which enlarges the attachment area to the substratum. In the third ‘full grown’ stage, the edge zone of the polyp tissue is retracted from the extended basal attachment to the calice, and upward growth of the coral predominates followed by lateral thickening of the septotheca, costae, septa and columella. Internal growth lines were found throughout the skeleton and may be composed of, or resulting from the presence of organic matter. The septotheca and the extended basal attachment, which are important for a strong skeletal structure and a strong attachment to the substratum, respectively, are probably thickened faster than the other skeletal elements. Attachment scars were found in areas where attachment of the coral tissue to the skeleton is critical.

This study demonstrates that the two species of lugworm, previously classified as Arenicola marina occupy distinct zones within sandy beaches around South Wales. Arenicola marina (sensu stricto) or blow lug, is found higher up the shore, tending to be concentrated at mid-tide level, whilst A. defodiens Cadman & Nelson-smith, 1993 or black lug is most numerous at or below mean low water of spring tides and, unlike A. marina in this area, also apparently extends subtidally. Arenicola marina is found in estuaries, unlike A. defodiens, and seems to inhabit slightly less exposed beaches. Degree of sorting, mean and median particle size do not appear to be a significant factor in determining lugworm distributions. Some possible explanations for these observed differences, including differences in burrow depth and salinity tolerance, are discussed.

Thirty-five specimens of the articulate brachiopod Neorhynchia strebeli were collected from a site at 814 m in the Weddell Sea. This was only the second species of the order Rhynchonellida to be found in Antarctica. Formerly N. strebeli was known solely from abyssal Pacific Ocean localities. A circumantarctic distribution is suggested in addition to the known deep-sea Pacific range. The specimens of this collection showed considerable commissure variation, suggesting that the previously proposed erection of two subspecies on the basis of this character is erroneous, and emphasises the phenotypic plasticity of some articulate brachiopods. The valve lengths and the number of alpha growth rings in the sample showed a normal distribution and a von Bertalanffy growth function was fitted to the data: Lt = 23 (1-exp[-0·228t]). If the alpha growth rings were of annual periodicity, the ages attained by the Antarctic N. strebeli of 11 y would be substantially lower than those reported for other Weddell Sea brachiopods. The epibiotic communities occurring on the valves of N. strebeli were impoverished, which is characteristic of deep water Antarctic brachiopods. The few specimens collected with their substratum were attached to small pebbles, but the typical attachment substrata may be different.

A series of field and laboratory experiments were conducted in order to assess whether the burrow-dwelling amphipod Corophium volutator, is a significant bioturbator of inter-tidal mud and sand flats where it often occurs at densities of tens of thousands per square metre. Comparisons of sediment characteristics, redox potential and meio- and macro-faunal populations in treatments with enhanced, natural and reduced densities of Corophium revealed effects on sediment physico-chemistry and on small meiofaunal-sized species, but these were weak and not always consistent. High densities of adult Corophium consistently depressed the abundance of smaller conspecifics although the mechanism of this interaction has not been identified. The results are discussed in the context of the ability of Corophium to promote the recovery of organically enriched sediments.

Mirocaris keldyshi gen. nov., sp. nov. is described from the Mid-Atlantic Ridge, TAG Location (26°09′N 44°50′W). The family Mirocarididae is proposed to include the new genus. The taxonomic position and distinguishing characters (presence of hook-bearing thoracic epipods and rudimentary appendix interna on pleopods 2–4) of the new family as compared to the other families of the superfamily Bresilioidea (Bresiliidae, Disciadidae, and Alvinocarididae) are discussed, and revised diagnoses for these families are provided.

Two aspects of the physiology of the burrowing shrimp Caliianassa tyrrhena (Decapoda: Thalassinidea) were studied in order to investigate the effects of the general pollution load: total (TRR) and weight-specific respiration rate (SRR) as well as the digestive enzyme activity of the digestive gland.

Caliianassa tyrrhena exhibited a very low respiration rate (mean TRR=64-29 μl 02 animal−1h−1, N=60; mean SRR=0·18 μl 02mg DW−1h−1, N=61).

The slope of the TRR-DW logarithmic regression (b=0·64) showed that respiration in C. tyrrhena is proportional to body surface. Size is the dominant factor (among size, sex, season and locality) determining the variation in respiration rate. Comparison between the two sites with the different pollution load showed that there were no significant differences in the respiration rates of the same size class and season, except for the youngest animals in summer which showed a significant decrease in their respiration rate at the polluted site.

A similar ‘inhibitory’ effect of pollution has been observed in the activity of the majority of the 19 digestive enzymes tested. Only three e.g., trypsin, β-galactosidase and α-glucosidase showed an increase in polluted waters.

One could suggest, therefore, that C. tyrrhena can be considered to be preadapted to the low oxygen conditions encountered in the sediments, because of its burrowing mode of living.

The process of larval release in field collected ovigerous Carcinus maenas was monitored in the laboratory using a time-lapse video recorder. Under constant light (L:L) and simulated natural light/dark cycles (L:D), larval release normally occurred in two or more main events at about daily and/or tidal intervals. Since larval release in the crab was expressed with circadian and circatidal periodicity in continuous light and in the absence of tidal cues, it suggests involvement of endogenous timing. Crabs showing daily larval release rhythms released larvae at various times of the day in L:L. In contrast, under simulated L:D cycles, 37 out of 38 crabs released larvae during the dark phase, suggesting nocturnal release of larvae in the crab under natural conditions. Larval release from freshly collected females which shed larvae within two days of collection occurred predominantly around the times of expected nocturnal high tide. When both local semidiurnal high tides occurred in daylight during long summer days, larval release appeared to start 2–3 h earlier than the expected morning high tide, before the onset of daylight. Larval release at the time around high tide, linked to a previously described larval tidal migration rhythm of ebb-phased upward swimming, is likely to have been selected for by enhancing the larval offshore dispersal process. Nocturnal larval release is probably adaptive in the avoidance of visual predators by ovigerous females as they release larvae.

The diversity and distribution of the Bivalvia fauna is examined in the various seas of Greek territorial waters. There is a statistically significant correlation between the bibliographical sources and the recorded variety of Bivalvia at any given area, with the deeper areas containing fewer species. Attention is given to some species ‘introduced’ into the area.

Cluster analysis, based on the species present at 30 regions which represent distinct geographical and ecological units, do not show any differentiation that corresponds to a geographical pattern. However, a distinct group is associated with the deeper open areas, which suggests that ecological parameters, such as depth and degree of enclosure, play an important role in the distribution of species.

Two bacteria-bearing mussels, Bathymodiolus brevior and B. elongatus, collected at five deep-sea hydrothermal sites from Lau and Fiji back arc basins (south-west Pacific), were analysed for polar and neutral lipids using gas-liquid chromatography mass spectroscopy (GLC-MS). The respective fatty acid distributions found in gills and mantles were compared to data from a Mediterranean littoral filter-feeding mussel, Mytilus galloprovincialis. The main characteristic common to the gills of the two vent mussels was the high level of (n-7) monounsaturated phospholipid fatty acids, which are supposed to originate from sulphur-oxidizing symbionts. Using palmitoleic, 16:1 (n-7), and vaccenic, 18:1 (n-7), phospholipid fatty acids as bacterial markers, endobacterial biomass was estimated to account for 2–10% of the vent mussel gill volume. Vent mussel tissues were poor in plant-derived polyunsaturated fatty acids, indicating the limited importance of the photosynthesis based material in the metabolism of these hydrothermal vent bivalves. It is suggested that some compounds, such as nonmethylene-interrupted dienoic fatty acids and specific trienoic fatty acids originating from elongation and desaturation of oleic and palmitoleic acids, respectively, were synthesized in order to substitute exogenous plant-derived polyunsaturated fatty acids considered as essential in marine invertebrates. The high level of neutral lipids in vent mussel gills suggests that these compounds are used as a major energy storage material. The neutral lipid/phospholipid ratio in gills emphasized the preponderance of the endosymbionts in vent mussel nutrition. Using this ratio as an index of the physiological state, the symbiosis patterns in different hydrothermal fields were compared.

Diel vertical migration (DVM) and in situ feeding of Thalia democratica (Tunicata: Thaliacea) was studied in the field (Agulhas Bank, South Africa) over a 48 h period in March 1994. Thalia democratica did not display DVM, and both aggregates and solitaires were mostly confined to the upper layers of the water column throughout the study period. Thalia democratica did not display any discernible diel feeding rhythm, and pigment content increased with salp size. Individuals with greatest pigment content were found at the chlorophyll maximum. Estimates of grazing impact varied with salp abundance and gut passage time, ranging from less than 1% to greater than 100% of phytoplankton productivity.

Monthly samples of fish from the intake screens of power stations at Oldbury and Berkeley in the inner Severn Estuary and Hinkley Point in the inner Bristol Channel, were used to analyse the community structures of the ichthyofauna in these regions. Marine species that use the estuary as a nursery area (marine estuarine-opportunists) were very abundant in the shallow inshore waters at Oldbury. Diadromous species were more abundant in the offshore and deeper waters at Berkeley than at Oldbury. Only one of the two species that complete their life cycles in the estuary was even moderately abundant in the inner estuary and the 15 freshwater species were relatively rare. Bass and particularly the sand goby complex were more numerous in the protected, inshore waters than the more offshore waters of the estuary. With the yellow and silver stages of the European eel, the reverse situation pertained. Seasonal changes in faunal composition were more pronounced in the inshore shallow than in more offshore deeper waters of the estuary. This largely reflected the sequential immigration of large numbers of the juveniles of marine estuarine-opportunist species into the former area for relatively short periods. Although the ichthyofaunal composition in the shallows at Oldbury underwent the same pattern of cyclical variation in each of five consecutive years, the degree of intra-annual variability differed, reflecting interannual differences in the recruitment strengths of the 0+ age classes of the different marine estuarine-opportunists. These cyclical changes were not correlated strongly with either salinity or water temperature. The faunal composition of the protected inshore, more marine waters of the inner Bristol Channel differed from those in both inshore and offshore regions of the inner estuary. The species which typified the fauna of the Channel were bib, poor cod, five-bearded rockling, sole and conger eel. Although the first four of these species were relatively more abundant in these waters than in the estuary, their juveniles often made extensive use of the shallows at Oldbury. This study emphasizes that, for some marine species, the protected inshore, and more marine, waters in the Bristol Channel can act as alternative nursery areas to those provided by the inshore shallows of the Severn Estuary.

The feeding habits of Trigla lucerna L. (1758) and Aspitrigla obscura L. (1764) (Pisces: Triglidae), off the coast of the Gulf of Valencia (Spain), were investigated between October 1989 and January 1991. The two species examined in this study appear to have distinct feeding types, based on the species composition of prey and the frequency of occurrence of major food items. Tub gurnard had a more diverse diet and fed mainly on crustaceans (mysids and decapods), teleosts and molluscs, whilst long fin gurnard were less piscivorous and fed mainly on mysids and natantids. No significant differences were found in the annual variation of vacuity coefficient for either species. Diet composition in these species did not show great changes with either season and size of fish. There was little dietary overlap between these two species.

Scats (N=200) of harbour seals (Phoca vitulina) were collected from haul-out sites on the Island of Mousa, south-east Shetland, during July, August and September 1994. A total of 5,531 fish otoliths were identified in scats and measured to reconstruct fish lengths and weight. Gadid fishes dominated the diet of harbour seals on Mousa during the study period, both in terms of weight and the frequency with which they occurred. There was evidence for the existence of temporal trends. Over the period July–September the importance of gadids in the diet increased while that of sandeels declined. These temporal trends are probably associated with changes in prey availability. Comparisons of the size of sandeels, herring and whiting eaten by seals with trawl catches suggest that seals were probably not size-selective, but a corollary of this is that, while otolith size is reduced during passage through seal guts, application of correction factors derived from captive feeding experiments led to over-estimates of fish size.

Histriobdella homari is a polychaete annelid belonging to the Order Eunicida and Family Histriobdellidae. Histriobdella homari is normally found in the gill chambers or among the eggs of the lobster Homarus vulgaris from the English Channel (Roscoff) and in the southwestern part of the North Sea (George & Hartmann-Schroder, 1985). Two independent sightings of H. homari living on the pleopods of Nephrops norvegicus from the Irish Sea and Clyde Sea area are reported.