This study aimed to identify the effects of different sieve mesh-sizes on processing time, the number of species retained, diversity measures and multivariate community analysis in the North Sea. Samples were collected at 63 sites throughout the North Sea and washed through two successive sieves, 10-mm and 5-mm mesh respectively.  Processing time for whole samples (5- and 10-mm fraction) averaged 91± 25 min compared with 55±16 min for the 10-mm mesh fraction. Altogether 40% of free-living species and 9% of attached species were recorded exclusively in the 5-mm fraction. The majority of these species were rare. Spatial gradients of species diversity and community structure were identical, independent of the mesh-size used. Multivariate community analysis showed no significant difference between descriptions of community structure based on fauna from 10-mm or 5-mm mesh.  The use of coarser sieving mesh would save time and money, if the aims of an epibenthic survey were to describe broad patterns of community structure and relative diversity. It would be possible to process approximately 50% more samples, if the time saved with 10-mm mesh were allocated to additional sampling. However, if information on single species is required, then sorting with the finer sieve mesh will yield crucial information. It was decided to employ a 5-mm mesh for epibenthic monitoring of the North Sea.

Deep or subsurface chlorophyll-a maximum (DCM) was studied at one station in the middle Adriatic from December 1996 to June 1998. Chlorophyll-a concentration, abundance, volume carbon concentration, size-fraction of phytoplankton and phytoplankton community structure were determined. In addition, physical and chemical factors as well as nutrients were determined. The DCM occurs during both the vertical mixing and stratification period in the middle Adriatic Sea. It is most frequent between 50 and 75 m. It is located below the pycnocline and it is associated with the nutricline. Phytoplankton size-fraction and community structure vary seasonally. The DCM is most pronounced during spring phytoplankton blooms with diatom dominance. Procaryotic picoplankton Synechococcus sp. was abundant in DCM during summer stratification. The DCM represents both a biomass maximum and a phytoplankton adaptation to low irradiance.

Short-term changes in zooplankton community structure and distribution in relation to changes in hydrological features were studied during summer in two distinct areas of Arcachon Bay (France) from July to September 1986. One sampling site was chosen in the northern part of the bay, influenced by oceanic inputs, and the other one in the south-eastern part of the bay, close to an estuarine zone, influenced by the River Leyre's inputs. Three different zooplankton assemblages were identified according to a temperature–salinity gradient: (i) an estuarine assemblage dominated by Acartia bifilosa and Acartia tonsa; (ii) an autochthonous assemblage composed of Acartia discaudata; and (iii) a coastal neritic one composed of Paracalanus parvus, Oncaea venusta and Penilia avirostris. All these latter assemblages remained stable during most part of the study period. However, a brief climatic event (storm event) occurred in mid-August and gave rise to a sharp decrease in temperatures along with significant changes in zooplankton structure and distributions in the bay. The estuarine community vanished and was replaced by the autochthonous community. In the northern part of the bay, the coastal neritic community succeeded the previously observed autochthonous community.  The effect of this brief climatic event was durable since recovery time lasted two weeks with regard to hydrological features and zooplankton communities. In addition, the climatic event also had ecological consequences since it permitted spreading of planktonic organisms from small-localized areas throughout the bay.

Results from the Continuous Plankton Recorder survey were used to study long-term changes in the zooplankton of four regularly sampled areas of the North Sea. The trends in α-diversity are described and analysed. Species associated with inflow of oceanic or mixed waters from the Atlantic or shelf to the west and south of Britain have increased in abundance or frequency of occurrence. Meroplankton have also increased but resident holoplankton and those associated with colder oceanic or mixed waters have declined. These changes have resulted in an increase in the species richness in the areas in the north-western North Sea. There was a period of low diversity in the late 1970s and early 1980s in the most southerly area, furthest from the sources of inflow. The evidence for a long-term trend was stronger than relationships between diversity and either the North Atlantic Oscillation or variation in position of the Gulf Stream in the western Atlantic.

Macro and meiobenthic communities of two fishing areas (Vilamoura and Lagos) in the western part of south Portugal (Algarve coast) were analysed. Both locations had been under severe dredge-fishing impact until four years previously. Vilamoura has since continued to be dredged, while fishing activity in Lagos was stopped in 1995 as a response to overfishing. For each location, three replicate areas were analysed at depths of 7–9 m. In each of these areas, 18 quadrats for macrofauna and 12 cores for meiofauna were randomly sampled by SCUBA divers during September 1999. The Shannon–Weiner diversity index was higher for meiofauna in the fished area, whereas macrofauna diversity was higher in the recently non-fished area. Bray–Curtis dissimilarity between the two areas was 87·82%. Major differences were found between Ampeliscidea, Amphiura mediterranea, Spisula solida, Haustoriidae, Nemertinea and Diogenes pugilator populations at the two sites. There was higher abundance but lower biomass of potential macrofaunal scavengers in the fished area, and carnivore biomass was also higher in this area. Deposit-feeders dominated meiofauna abundance in both study areas. The community structure of the continuously fished area was dominated by small, opportunistic, short-lived species while the community structure of the recently non-fished area was dominated by more fragile and long-living sessile organisms.

The sphaeromatid crustacean isopod genus Campecopea is revised, a new diagnosis given and the genus Anoplocopea Racovitza, 1907, is placed in synonymy; the type species Campecopea hirsuta is redescribed and Campecopea lusitanica comb. nov. is recorded from the Canary Islands and Azores. The four species of Campecopea differ from each other principally in the presence or absence of a prominent posteriorly directed dorsal process on the male pereonite 6, the ornamentation of the posterior pereonites, the shape of the uropods and also the fine details of the dactylus accessory spine (smooth or serrate).  The phylogenetic significance of dorsal process is re-evaluated here, and the character discussed in relation to Campecopea, Dynoides and Clianella, and several other sphaeromatid genera. It is regarded that the interpretation of this character as being of intrinsic generic merit has resulted in the over splitting of several genera and also the creation of paraphyletic genera. It is suggested that reappraisal of sphaeromatid generic characters in cladistic terms is a necessary first step in terms of establishing the monophyly of many sphaeromatid genera.

The behaviour of two ectosymbiotic animals, Peregrinamor ohshimai (a bivalve attached to the ventral cephalothorax of the host), and Phyllodurus sp. (a bopyrid isopod attached to the second pleopod of the host), during ecdyses of the host thalassinidean Upogebia shrimps was studied by time-lapse video of infested shrimps. In the intermoult stages of the hosts, both ectosymbionts did not move. However they moved on to the newly emerged body of the host at the time when the host moulted. Peregrinamor ohshimai began to move just after the host started moulting, whereas Phyllodurus sp. moved prior to ecdysis of the host and waited near the fissure from which the newly moulted body emerges first. There are highly correlated morphological relationships between the symbionts and the hosts. It is suggested that both ectosymbionts grow with the same host individuals after infection, keeping morphological affinity with their hosts without being discarded during ecdyses of the hosts.

Adults of the isopod Paragnathia formica inhabit burrows in saltmarsh banks from which they release larvae during autumn high tides. Larvae pass through three moult stages, each of which feeds ectoparasitically on estuarine fish (including Pomatoschistus microps), before a final moult to a non-feeding adult stage. The entire energetic reserves for survival and reproduction up to nine months (females) or 16 months (males) later are therefore acquired during these three brief periods of parasitism. Application of a plankton sampling technique showed larval density in the water to vary considerably between successive high tides. High densities of larvae (1 per 1·2 l) occurred on only one tide during a week-long study, when a corresponding peak in parasite prevalence in the fish population (10%) was recorded. Peak larval release was observed as the tide rose, at a time when host fish have been reported to be in greatest abundance. Considerable larval longevity was demonstrated in the laboratory in the absence of food (mean=43 d). Data are interpreted, in conjunction with field observations, in relation to larval parasitism opportunities post-birth.

The qualitative and quantitative monthly composition and the annual temporal changes in a shallow (3·3–6·3 m) community of Crustacea: Decapoda associated with soft bottoms (very fine–muddy sand) and the seaweed Caulerpa prolifera in the south of Spain (Valdelagrana Beach in the Bay of Cadiz) has been studied for two years from February 1994 to January 1996. This community showed a similar pattern in both analysed cycles and could be characterized by a change or succession in the abundances of two groups of species: in autumn–winter Hippolyte inermis and Hippolyte varians (species associated with seaweeds); and in spring–summer: Philocheras monacanthus, Diogenes pugilator (characteristic of sandy bottoms) and Macropodia parva. The results of the ordination analysis of monthly samples is related to the absence or abundance of these dominant species although it does not define the two seasonal groups. The analysis of monthly richness, equitability, diversity and k-dominance curves, during the two years, showed a stable and rich community (with more than 6100 specimens caught belonging to 49 species) despite the human influence and the proximity of the Guadalete River.

The shell selection and utilization patterns of three sympatric hermit crab populations (Clibanarius antillensis, C. sclopetarius, and C. vittatus) and shell availability were studied in a tropical intertidal low energy area. Shell availability (except for C. antillensis) was low and the hermit crabs showed overlap in size (mainly C. sclopetarius and C. vittatus). The influence of shell availability and selection on shell use was dependent on crab species. Clibanarius antillensis used mainly shells of Cerithium atratum, the most available shell species, while Clibanarius sclopetarius and C. vittatus occupied shells with lower availability in the studied area such as Chicoreus senegalensis, Stramonita haemastoma, Leucozonia nassa and Cymatium parthenopeum. The three species selected different gastropod shells with only Clibanarius antillensis using almost exclusively its preferred shell species in nature. The relationship between shield length and the weight of the used shell was not dependent on crab species or shell species, indicating that the size (not species) of the shells defines what size (not species) of crabs will occupy them.

The fecundity of Liocarcinus depurator (Decapoda: Brachyura) in the Ría de Arousa (Galicia, north-west Spain) and the reasons why it fluctuates were analysed, comparing the results with data available from other geographical areas. The incubation of L. depurator eggs in the Ría de Arousa generally takes place between January and September, although ovigerous females can be found all year round. The number of eggs per brood in L. depurator varied considerably in the Ría de Arousa and ranged from 5265 (carapace width (CW=31·3 mm, stage III) to 203,724 (CW=44·6 mm, stage I). The allometric equations adjusted to fit each egg development stage indicated that there was a strong positive correlation between female body size and the number of eggs the animal is able to bear. Female body size, measured as the carapace width, was the main factor causing variability in the fecundity of L. depurator. The second most important cause of variability in the development stages of the eggs was the number of eggs per brood, which may be due to the gradual loss of eggs that occurred during the incubation of these eggs in the female abdomen. Temporal changes constituted another significant factor in the variability of the fecundity of L. depurator. The allometric equations (log F=log a+b×log CW) fitted to each month and development stage I presented changes in the slope which point to the existence of a temporal evolution in the number of eggs. In the Ría de Arousa and for all the development stages, L. depurator was found to have a significant negative correlation between the number of eggs per clutch and egg volume. Egg volume also correlated negatively with the size of the female in stages I of the egg development. The degree of correlation between the volume and number of eggs was greater than the correlation between volume and size. The main cause of the variability in the egg volume of L. depurator in the Ría de Arousa may be attributed to the development stage (ANCOVA, P<0·001).

Laboratory assessment of barnacle cyprid settlement showed that it was increased by a multiple of ∼6 and by a multiple of ∼3 by the pedal mucus produced by Patella vulgata and by Littorina littorea, respectively. Field experiments showed that pedal mucus produced by P. vulgata could increase cyprid settlement by a multiple of ∼4, but that there was no effect of the pedal mucus produced by L. littorea. Evaluation of the effect of pedal mucus coated with nitro-cellulose and various pedal extracts, on cyprid settlement, ascertained that there appeared to be no chemotactic or chemotaxic effect of pedal mucus on cyprid settlement. In contrast, the use of a physical analogue to pedal mucus, silicon grease, increased cyprid settlement by a multiple of ∼18.  Pedal mucus produced by P. vulgata and by L. littorea increased the time spent by cyprids in surface suitability testing by a multiple of ∼10 and ∼3, respectively. Only the pedal mucus produced by P. vulgata had any effect on the exploratory behaviour of cyprids increasing the time spent on this behaviour by a multiple of ∼3. Pedal mucus affects the settlement of cyprids through adhesive enmeshment, resulting in positive feedback to the mechanoreceptors housed in the antennules of cyprids, in what is effectively a settlement cascade. Pedal mucus produced by P. vulgata and L. littorea can affect the settlement of the majority of settling marine organisms through physical entrapment. Pedal mucus produced by L. littorea will have little, if any, effect on the settlement of organisms in the field whereas the pedal mucus produced by P. vulgata may be of major importance in determining the adult distribution patterns.

Surface characteristics including wettability, thickness and adhesive potential of the pedal mucus produced by Patella vulgata and Littorina littorea were measured, to determine their effects on the settlement of marine organisms. The pedal mucus produced by P. vulgata was less wettable than that produced by L. littorea. For organisms that prefer to settle on hydrophobic substrata the pedal mucus produced by P. vulgata would be their preferred settlement site. The pedal mucus produced by stationary P. vulgata was thicker (mean thickness±SE=0·37±0·004 mm) than the pedal mucus produced by mobile P. vulgata and/or that produced by L. littorea, neither of which differed in their thickness (mean thickness±SE =0·10±0·01 mm).  The pedal mucus produced by P. vulgata had a greater adhesive potential (mean force of adhesion for the size range of mimics examined=3715–5380 Nm2) than the pedal mucus produced by L. littorea (mean force of adhesion for the size range of mimics examined=2846–3361 Nm2). Comparison of the adhesive potential of the pedal mucuses with a pedal mucus analogue, silicon grease, suggests that the pedal mucuses function as a Stefan (1874) adhesive when adhering organisms.

This is the first study to examine the seasonal biochemical composition of tissues from male and female Cucumaria frondosa. Gonad and body wall tissues were analysed for their protein, lipid, and glycogen content. Lipids were the single most abundant component in gonad tissues, followed by proteins and glycogen, for both males and females. However, only protein and glycogen in the gonad tissues differed between feeding and non-feeding periods as well as between pre- and post-spawning periods. Proteins and lipids were both more abundant than glycogen in the body wall tissues. In this case, only protein and glycogen were found to differ between spawning states. All differences observed in the gonad tissues were attributed to the annual reproductive cycle, which produces a need for nutrient storage to allow the production of gametes throughout the year. The body wall was thought to be responsible for the build up of reserves during the feeding period in order to support maintenance and reproduction during non-feeding months.

Data from bottom trawl surveys conducted each summer, winter and spring on the Cretan shelf from 1988 to 1991, were used to study the age, growth, maturity and bathymetric distribution of red pandora (Pagellus erythrinus). The good agreement of back-calculated and observed lengths-at-age with length frequencies and the marginal increment analysis, supported the annual nature of scale marks. A comparison of available growth data from the Mediterranean and the Atlantic revealed higher lengths-at-age for red pandora in the north-western Mediterranean and the Atlantic than in the central and eastern Mediterranean. The auximetric analysis, i.e. the double logarithmic plot of the parameter K of the von Bertalanffy growth function vs asymptotic length (L∞), showed a strong negative relationship for the central and eastern Mediterranean data set, implying a common ‘growth space’ for the populations in these areas. Lengths-at-maturity were lower on the Cretan shelf than in the Atlantic. These differences were attributed to the synergistic combination of trophic and thermal conditions.  Depth, temperature and salinity data were combined with biological data on abundance, fish size, age and maturity. In general, mean size increased with bottom depth because smaller individuals tended to be found in shallower and warmer waters. Individuals having reached first maturity were mainly distributed in the periphery of the algal/angiosperm meadows (60–80 m). All detailed studies of the bathymetric distribution and movements of shelf-dwelling demersal species (Mullus barbatus, Mullus surmuletus, Lepidotrigla cavillone and Pagellus erythrinus) in the Mediterranean show that these species are characterized by a spring–summer spawning season, a high concentration of spawning adults at mid-shelf depths, and nursery grounds located in the vegetated shallows. This multispecies pattern might have an adaptive function with both ecological and management implications.

The full developmental embryonic sequence of Gobius cruentatus is described for the first time. Embryonic development lasted 13 days (14·0–15·0°C). The newly hatched larvae (3·3 mm total length) presented pigmented eyes, the yolk is fully absorbed, and the mouth and anus were opened allowing the onset of exogenous feeding almost after hatching.

Arsenic compounds in aqueous extracts of muscle, liver, kidney, and lung tissue taken from a sperm whale Physeter catodon (Mammalia: Cetacea) beached on a small island near Phuket in the Andaman Sea were determined by high performance liquid chromatography using an inductively coupled plasma mass spectrometer as the arsenic specific detector. The total arsenic concentrations in the tissues (dry mass) were low, ranging from 0·3 μg g−1 for liver and lung, to 1·0 μg g−1 for muscle and 3·0 μg g−1 for kidney. Most of the arsenic (>60%) was extracted from the tissue into water, and the bulk (>80%) of this arsenic was present as arsenobetaine. Dimethylarsinate was present at low levels in all four tissues whereas arsenocholine was detected in kidney, liver and lung, but not in the muscle tissue. Another arsenic containing betaine, trimethylarsoniopropionate, was also present in all four tissues. This is only the second report of trimethylarsoniopropionate as a naturally-occurring arsenic compound.

The effect of water flow rate on the regeneration rate of the temperate sponge Cliona celata was investigated at two sites experiencing fast and slight current flow respectively at Lough Hyne, Co. Cork, Ireland. Faster regeneration rates were found in sponges living in high current areas which may be due to an increased amount of potential food material per unit time and the possibility of entrained water flow.

A new species of the genus Rosacea (Siphonophora: Calycophorae: Prayidae) is described from the Gulf of Oman, where its eudoxid stage was found in abundance. It is distinguished from other Rosacea species by the course of the lateral radial canals on the nectosac of the nectophore, and the shape of the eudoxid bract and the arrangement of its bracteal canals.