The spread of the oil spill from the tanker ‘Prestige’ was analysed in relation to the occurrence of the exceptional 2002/2003 Navidad using airborne and AVHRR satellite measurements. Altimeter-derived geostrophic velocity and Envisat ASAR observations were also used to investigate the structure of this Cantabrian extension of the poleward current around Iberia.

Phytoplankton photosynthetic quantum efficiency (PQE), pigments, absorption characteristics, species composition (converted to phytoplankton carbon, Cph) and other variables were measured at an offshore site in the western English Channel throughout 2001, using an opportunistic weekly sampling schedule. The variation of chlorophyll-a (Chla) and other phytoplankton pigments followed the classical seasonal cycle, driven by incident light, patterns of stratification and nutrient availability. Phytoplankton and pigment concentrations were low in the winter, rising to a peak in the spring ‘bloom’, with episodic blooms throughout the summer, an autumn bloom and a decline to the winter minimum. Surface layer Chla and total pigment (Tpig) concentrations were highly correlated for the whole year, yet it was observed that the fraction of Chla in Tpig (Chla/Tpig) was not constant and had a distinct seasonal pattern, low in winter and higher in spring, summer and autumn blooms. Chlorophyll-a/Tpig was linearly correlated with recent ambient light fluxes and maximum PQE (PQEm) throughout most of the year, though more significantly within seasonal periods. Chlorophyll-a and Tpig were both linearly correlated to Cph and the Chla/Cph ratio was significantly correlated with both Chla/Tpig and PQEm. Also the optical absorption ratios, a674/a443 and a674/a490 were significantly correlated with PQE and Chla/Tpig, indicating probable optical signatures for these two parameters. The seasonal cycle of measurements of photosynthetic quantum efficiency provided a bench-mark against which all the photosynthetically-driven seasonal changes of biological properties can be understood, in terms of incident solar radiation and nutrient availability. We conclude that phytoplankton synthesize Chla preferentially to other pigments or carbon compounds in conditions beneficial to growth. The PQEm, the ratios of Chla/Tpig, Chla/Cph and a674/a443 are greater when plants are growing actively. In periods of nutrient sufficiency, PQEm, Chla/Tpig and a674/a443 are all linear functions of the mean total photon flux for the recent few days. Photosynthetically driven changes in Chla synthesis, cause observed changes of Chla/Tpig and Chla/Cph ratios.

The diversity and structure of meiobenthic nematodes and macrobenthic infauna were studied at four widely spaced subtidal sites around the UK coast in relation to a number of measured environmental variables. The stations were situated on soft sediments at water depths of 53 to 95 m and are intended as long-term monitoring locations as part of the UK National Marine Monitoring Programme. Similar benthic assemblages were encountered in comparable environmental conditions. The distribution of nematode and macrofauna species was mainly governed by the geographical location of the habitat and the granulometric composition of the substrate. There was no evidence of any adverse effect on the measures of benthic assemblage structure arising from trace metal concentrations in the sediment, indicating the relatively unpolluted nature of the offshore locations under investigation. Nematode and macrofauna assemblages exhibited stable patterns over time periods of three years.

The trophic interactions between primary consumers and the organic matter sources in a man-made intertidal ecosystem were investigated. The most representative invertebrates that occupied the different habitat types tend to use similar food sources, namely benthic diatoms and suspended particulate or sedimentary organic matter, although they do so in different proportions. Fucus vesiculosus was abundant on the rocky substrate but this macroalga nor its epiphytes contributed importantly to the diet of the primary consumers inhabiting these assemblages. In contrast, benthic diatoms from the nearby mudflat were directly used as a food source because of their re-suspension in the water and transport by the tide to the artificial rocky shore. The results suggested that the trophic pathways in this intertidal environment were relatively simple.

The long term effects of macroalgal canopy removal on community composition were investigated over a 12 year period. Experimental removal of the dominant Ascophyllum nodosum canopy led to short term changes in community composition, the major features of which were still apparent 12 years later. Ascophyllum was slow to recover despite high recruitment, and experimental plots were dominated by Fucus species. After 12 years a mixed assemblage of Fucus serratus, Fucus vesiculosus and Ascophyllum had developed. Canopy removal resulted in a change in the balance between grazing limpets and the cover of red algal turf in the understorey community. The cover of turfing algae declined significantly allowing the area grazed by limpets to extend. This led to a 3–6 fold increase in the limpet population 12 years after canopy removal.

The population biology and habitat of Haliclystus auricula was studied from samples taken every two months in southern Chile between November 2001 and November 2002. A total of 3790 medusae were collected and examined. The abundance of H. auricula varied seasonally. Maximum densities occurred in summer (1405/m2) and minimum densities during the winter, when the population gradually disappeared. Gonads were observed in medusae starting from a size of 2·0 mm. Stauromedusae were found most often on the red filamentous alga Ceramium rubrum (69%), followed by Gymnogongrus furcellatus (12%) and Ulva sp. (10%). There were highly significant differences in mean abundance of medusae on these three algae (P<0·05). The remaining 9% of medusae were found on other seaweeds. The smallest medusae (0·08–0·9 mm umbrella height) were found exclusively on C. rubrum. The highest densities were recorded in the midlittoral zone.

The diet of Haliclystus auricula was studied from the gut contents of Stauromedusae collected every two months in southern Chile between November 2001 and November 2002. A total of 3790 medusae were collected and examined. Stauromedusae prey consisted primarily of harpacticoid copepods (68·4%), followed by gammarid amphipods (15·4%), chironomid fly larvae (9·2%) and podocopid ostracods (5·9%). The remaining 1·1% of the diet was made up of empidid fly larvae, polychaete worms, isopods, juvenile decapod crustaceans and gastropods. Gut content was observed in 31% of the stauromedusae collected and only in medusae with an umbrella height greater than 0·4 mm. Frequency of medusae with prey items in their gut content increased with stauromedusae size. The type of prey most frequently found in the smallest medusae were copepods, whilst larger individuals contained mainly amphipods. A strong tendency for the length of prey consumed to increase with medusae size was found.

Typical marine arthropods (crustaceans and halacarid mites), as well as species of recent terrestrial ancestry (insect larvae and mesostigmatid mites) coexist on mangrove pneumatophores. Both groups are affected by desiccation and are less abundant towards the tips of the pneumatophores. The degree of species associations within and between the two groups was investigated. The number of negative associations is higher for marine–marine, as compared to terrestrial–terrestrial and terrestrial–marine species pairs. When environmental stress (as represented by direct sunlight, and elevation on pneumatophores, both resulting in increased desiccation) is considered, associations tend to shift from negative to positive, and this is more obvious in terrestrial–terrestrial species pairs. These results are attributed to the longer co-evolutionary history of the marine species, resulting in a more precise partitioning of the microhabitats, while the relationships between terrestrial species are less stable, and more susceptible to environmental stress.

The caprellid amphipod Caprella danilevskii was exposed to five levels (0, 10, 100, 1000 and 10 000 ng l−1) of tributyltin (TBT) both in the embryonic stage (5 days) and over its whole life history from hatch to death (50 days) to examine the effects of TBT exposure on survival. In both experiments, survival rate decreased drastically as TBT concentrations increased, with a decrease occurring even at 10 ng l−1 in both short- and long-term exposure experiments. Significant differences were found in the survival rate between the control (no control specimens died) and the three concentration groups except 10 000 ng l−1 (all specimens died), regardless of sex. However, the survival rate in response to exposure to TBT has been found to be similar among all combinations of TBT concentration except 10 000 ng l−1, in both sexes. Furthermore, no significant differences were observed in the survival rate in response to exposure to each concentration of TBTCl between sexes. These findings suggest that the risk of survival in response to exposure to TBT between sexes is similar in the caprellids. No sex-specific differences of mortality by TBT exposure were observed in the species although feminization by TBT exposure was found in the caprellids in a previous study. These results all lead to the conclusion that TBT disturbs the mechanism of sex determination during the embryonic stage of the species.

Trachysalambria curvirostris occurs widely along the south and west coasts of Korea with a range extending from Kanghwado in the north-west, down to Sarangdo in the south-east. With seasonal warming of the waters starting in April, the shrimps begin to migrate from deep waters to the coastal area. Zoea and mysis larvae occurred from June to August. Sex ratio showed seasonal variations, with a mean value of 56·7% for the females. The species produces one cohort a year, with the ovaries ripening from June to July. Insemination appeared to take place from June to August, as more than half of the females sampled in the study over 15–16 mm carapace length were inseminated. Mean gonadosomatic index (GSI) reached a maximum between June and July. The smallest mature female found was 15 mm carapace length (CL). Size at 50% sexual maturity (CL50), determined from both mature females and inseminated females, was 15·37 mm and 16·49 mm CL, respectively. Fecundity was directly proportional to the size of the female, with clutch sizes varying from 16,380 eggs in the smallest female to 114,621 eggs in the largest, and the eggs ranged from 230 μm to 340 μm in diameter. The life span of females appeared to be 14–15 months according to size frequency distributions, while that of the male was 13–14 months. Population growth was estimated by the modified von Bertalanffy growth function incorporating seasonal variation in growth. Based on the growth parameters (K=2·00 y−1 and L∞=24·64 mm CL for females, and K=2·00 y−1 and L∞=19·00 mm CL for males) growth curves showed that females grew faster and reached a larger size at age than males. This result is supported by differences in growth performance indices (ϕ′).

Munida subrugosa is the most abundant galatheid crab species in the Beagle Channel (55°S 68°W) off Tierra del Fuego, Argentina. Samples of crabs and the epibenthic community were taken on a monthly basis at two different depth strata (<40 m and >70 m), by means of epibenthic trawling from 1998 to 1999. Stomach contents from 1582 crabs were analysed, out of which only 2% had empty stomachs. The quantity of food in the stomach contents was clearly seasonal and similar at both depths. The organic matter varied throughout the year and between both depths, being significantly higher in summer/spring than in autumn/winter. Munida subrugosa shows two different and simultaneous feeding habits: (1) as a predator M. subrugosa feeds on crustaceans, algae, and polychaetes; and (2) as a deposit feeder M. subrugosa consumes particulate organic matter and organisms associated with the superficial layer of the sediment. The composition of the diet of Munida subrugosa was similar for both years, and independent of depth, sex or season. Munida subrugosa selected crustaceans only in autumn and winter, whereas most food items were found according to their availability in the habitat.

The predatory effects of Pachygrapsus marmoratus on populations of the intertidal limpet Patella depressa were analysed on rocky shores located on the central coast of Portugal. Nocturnal observations on crab feeding behaviour were conducted and experimental exclusion cages were set in the substratum to assess density effects on limpets. The results indicated that although crabs feed on adult limpets the predatory level was minimal. Crabs used consistent tactics to detach limpets from the substratum but the majority of the attacks were unsuccessful, possibly due to morphological and behavioural adaptations of limpets. An alternative recruitment hypothesis is advanced to explain non-significant differences between experimental treatments and a possible predatory role on shaping levels of recruitment on lower levels of the shore is considered.

The populations of three sympatric hermit crabs, Pagurus excavatus, Anapagurus alboranensis and Anapagurus petiti were studied in a shallow (15–25 m) sandy area in the north-western Mediterranean. Seasonal abundance, seasonal size frequency, sex ratio and reproductive periods were examined. Pagurus excavatus was the largest and most abundant species in the zone. Pagarus excavatus and Anapagarus alboranensis are sexually dimorphic in relation to size, with males reaching larger sizes than females. However, the males and females of Anapagurus petiti reach similar large sizes. Anapagurus petiti has a sex ratio that is female biased, whereas A. alboranensis and P. excavatus are 1:1. Anapagurus petiti showed a higher reproductive activity during warmer seasons, while in A. alboranensis the proportion of ovigerous females was high throughout the year, with a minimum in autumn. The activity and clutch size of P. excavatus decreased during summer.

Multiple locus allozyme heterozygosity has been shown to be weakly, but significantly correlated with certain fitness parameters in bivalves. Immune function of individual Mytilus edulis from the Menai Strait, Wales, UK was assessed monthly over one year (1997–1998) by measuring total blood cell (haemocyte) counts, differential haemocyte counts (% basophils and eosinophils), phagocytic capability (by zymozan uptake) and intracellular superoxide generation. Sampled mussels were also scored at 9 allozyme loci. Mussels were then grouped into multiple locus heterozygosity (MLH) classes and plotted separately against the different measures of immunocompetence. No significant association was present between MLH and total haemocyte count, phagocytic capability or intracellular superoxide generation. However, there was a significant association between MLH and the character (basophilic or eosinophilic) of circulating haemocytes (r2=0·057, P=0·002). Highly heterozygous individuals tended to have significantly more eosinophilic haemocytes circulating in the blood than highly homozygous individuals. Eosinophilic haemocytes are known to have a high capacity for phagocytosis of invading organisms and these results may therefore be interpreted as increased health (=fitness) in more highly heterozygous individuals.

Sex ratio and size–gender distribution of Coralliophila meyendorffii and Babelomurex cariniferus collected in the field was studied. While sex ratio did not depart from the expected Fisher 1:1 ratio for dioecious species, the size–frequency distributions showed clearly a sexual size dimorphism with males significantly smaller than females. Laboratory monitoring of penis reduction in both species, combined with an anatomical and histological study of the reproductive system of individuals reducing penis revealed the existence of transitional sexual stages, proving the existence of protandry. Penis monitoring also demonstrated a high plasticity in size at sex change, suggesting a socially controlled sex change. In C. meyendorffii, where penis monitoring followed an experimental design based on the assumption that protandry existed and that presence of females influenced sex change, results strongly supported a social control of sex change. Evidences for protandry in other coralliophilids are summarized and protandry as a widespread sexual strategy in Coralliophilidae is postulated.

Population differences were measured in the tolerance of Littorina saxatilis from sites around the Isle of Man, to acute exposure to zinc, lead, copper and cadmium. Animals from a site influenced by disused mine run-off in Laxey estuary (high zinc) were compared with animals from less contaminated estuaries (Peel-high lead, but lower zinc), and the relatively uncontaminated Castletown and Ramsey estuaries, plus the open coast near Derbyhaven. Median lethal times (LT50) were estimated for each test concentration (5, 10, 20 mg l−1 Zn; 5, 10 mg l−1 Pb; 0·5, 1·0, 2·0 mg l−1 Cu and Cd) except for those that did not produce sufficient mortalities. Individuals from Laxey estuary showed significantly higher tolerances to zinc (10 mg l−1) and lead (5 mg l−1) than animals from the unpolluted sites. No co-tolerance to copper or cadmium was apparent. Population tolerance to zinc was correlated with reduced accumulation rates. Lead tolerance may result from the ability of the tolerant individuals to sequester the metal and detoxify it in their tissues; the littorinids from Laxey had significantly higher rates of lead accumulation.

The age of the sea urchin Hemicentrotus pulcherrimus in Oshoro Bay at the northern distributional limit of the species was ascertained by counting black bands in charred genital plates after etching. Consequently, the seasonal growth of two year-classes was monitored and the seasonal changes were related to the reproductive cycle and water temperature. A black band at the edge of the genital plates was found in more than 50% of the sea urchins from September to November. No statistical difference of the test diameter and body weight forming the bands between the estimated and actual values showed that the band is formed annually and can be used as a chronometer. The sea urchin grew rapidly for one and a half months, from late August to late September or early October when water temperature reached a maximum of >20°C, then began to fall while the gonads increased in size prior to maturation. Growth ceased during October to November with initiation of gonadal maturation and the peak of black band formation in genital plates. Spawning occurred from March to May, later than in southern Japan. The annual cycle of growth and reproduction of H. pulcherrimus may be flexibly adapted to surbarctic waters.

Vertical posture has been studied only in the scutellid sand dollar Dendraster excentricus although it has been reported in another Dendraster species and two species of laganid sand-dollars. The vertical posture has been associated with the posterior eccentric position of the apical system and petals of the test. We have discovered the scutellid sand dollar Encope michelini, which shows no eccentricity of the apical system and petals, also has the vertical posture in the population studied. Absence of eccentricity of the apical system and petals in living and fossil sand-dollars does not indicate absence of the vertical posture.

The reproductive cycle of a local population the aspidochirote Holothuria tubulosa in Kaštela Bay (Adriatic Sea) was analysed from July 1994 to August 1995 by histological examination and observations of macroscopic features of the gonads. Five gonadal stages were described: recovery stage, growing stage, mature stage, spawning stage, and post-spawning stage. The distinguishing features used to describe gonad stages in both sexes included the main features of reproductive cells and gonad wall. The reproductive cycle showed a clear annual pattern and was synchronous in both sexes. Spawning occurred during the warm season, from July to September, when the surface water temperature ranged from about 22°C to 26°C. From October to January individuals were in resting phase and had no gonads. In both sexes, variations in maturity indices were related to the seasonal changes in temperature.

During January 2003 the bathymetric distribution of the cephalopod fauna of the South Georgia and Shag Rocks slope (100–900 m) was investigated using a commercial bottom trawl. Forty-four trawl stations caught 193 cephalopod specimens including six species of octopod and seven of squid. The benthic octopods Pareledone turqueti and Adelieledone polymorpha were abundant in shallow water at South Georgia, being replaced by Thaumeledone gunteri in greater depths. However, neither A. polymorpha nor T. gunteri were caught on the adjacent Shag Rocks area. Two specimens of the deep-sea genus Graneledone were caught on the South Georgia slope. The most abundant squid species caught were Moroteuthis knipovitchi, Psychroteuthis glacialis and Slosarczykovia circumantarctica, which are primarily pelagic and may have been taken when their vertical migrations impinged on the slope.