Winter cooling and persistent mixing for more than a quarter of year (November to early March) along the North Eastern Arabian Sea (NEAS) results in nutrient enrichment of the euphotic column thereby triggering biological production. Hydrographic characteristics of NEAS during Late Winter Monsoon (LWM) and Early Spring Inter Monsoon (ESIM) and the influence on biological production are overviewed here. Winter convective mixing signatures were evident during LWM with low SST (24°C), high SSS (36.4), deep mixed layers (>100 m) and increased surface nitrate (~1 µM). Open ocean waters observed high chlorophyll a (1–2 mg m−3) and microphytoplankton abundance (1.2–1.5 × 104 cells l−1). Diatoms and green Noctiluca scintillans were the major microphytoplankton identified. ESIM observed gradual stabilization of water column with curtailment of winter signatures and strengthening of Noctiluca scintillans blooms. Mesozooplankton biomass was higher during LWM and decreased towards ESIM with intensification of Noctiluca blooms. However during ESIM, abundance of gelatinous zooplankton occurred in the bloom region. Inter-annual variations were observed in the biological responses along with the hydrographic changes. Thus the convective process during winter monsoon and stabilization of the water column during ESIM plays a significant role in the production pattern of NEAS.

Although Aplysia depilans is a widely known European species and the type species of the genus, the distinctions that separate it from other related congeners are not entirely clear. Aimed at improving this scenario, a detailed morphological description is performed herein, showing some unprecedented and useful features. Based on our anatomical examination, this study has found the opaline gland to be dark in colour, as well as a metapodium with an indistinctly delimited pedal sucker, a crop divided into two equal chambers of similar volume by a circular muscle, gizzard plates arranged in groups, and a peculiar penial sheath structure. All of these characters appear to be significantly different from the other species, based on a review of the anatomical literature and several examined samples of ongoing studies. Our central objective is to provide new data on the anatomy of the type species of Aplysiidae; and, based on topological evidence, to propose a new terminology and possible homologies to some important characters, such as parapodia lobation, cephalic tentacles, crop, penial sheath, gizzard plates and visceral ganglion in anaspideans, for future phylogenetic analysis. The subgenus Subaplysia Medina, Collins & Walsh, 2005 is regarded as a junior synonym of subgenus Aplysia Linnaeus, 1767.

Population parameters and behaviour of the herbivorous fish Sarpa salpa, present differences between protected and non-protected seagrass meadows of the north-western Mediterranean Sea. Larger individuals are more abundant inside protected areas, where their grazing pressure on seagrass is disproportionately greater than that of smaller fish feeding on algae and seagrass in unprotected areas. The feeding rate (bites per minute per individual) of smaller fish in unprotected areas is relatively high; however, the denser populations of larger fish in protected areas consume more forage because individual mouth gape is greater and larger fish remove more forage per bite. All these differences suggest a higher impact on seagrass meadows inside protected areas.

Aquarium systems allow technically sophisticated experiments that promise new opportunities to answer urgent questions about reef coral biology, for instance assessing the responses to decreasing environmental pH and/or increased temperatures. Over recent years, long-term culture and (predominantly asexual) propagation of corals has become possible in such systems. At present however, only limited data are available that clarify whether or not responses of the coral holobiont are dominated by the acclimatization to life in captivity or continue to reflect, for example, taxonomic differences seen in nature. We studied the diversity of the symbiotic algae in corals and sea anemones after long-term aquaculture by analysis of their small subunit (SSU) ribosomal DNA gene. A field sample of Acropora clathrata from the Arabian Gulf which was used as a control contained clade C zooxanthellae. The aquarium corals also harboured clade C symbionts, but sequencing of the SSU DNA suggested that the analysed animals host different subclades. A prevalence of clade C is also found among corals from the Indo-Pacific region, the origin of most of the aquarium samples. An individual of the temperate sea anemone Anemonia sulcata (viridis) contained clade A symbionts, similar to those found in nature, even after nearly 10 years of co-culture with sea anemones (Entacmaea quadricolor) and corals hosting clade C symbionts. The results indicate that the specific host–symbiont association occurring in nature appears to persist over >2 years timescales in captivity, with no mixing of symbionts between hosts maintained in the same aquarium or apparent selection of stress-tolerant symbiont strains such as clade D.

In this study the digenean parasites in the mud snail Hydrobia ulvae at two sites were compared for a period of one year. The sites were the north shore of Belfast Lough (Northern Ireland) and the Bend of Tarty on the Ythan Estuary (north-east Scotland). Samples of snails were collected monthly from which 13 species of digenean larvae were recorded at Belfast Lough. Two of these species were absent at the Bend of Tarty. Overall digenean prevalence was very similar at each site indicating that the respective bird communities were composed of ecologically equivalent species. Differences in the prevalence of individual digenean species are discussed in relation to the abundance of definitive and/or secondary intermediate hosts at each of the sites. Both sites displayed similar seasonal patterns of parasite prevalence with sharp increases to around 25% in the summer months. Snail shell heights were greater at Belfast Lough than at the Bend of Tarty and a positive correlation between snail shell height and infection by trematode parasites was recorded at both sites. Increased parasite prevalence in larger snails was attributed to factors such as age-related susceptibility and/or parasitic castration of the snails.

A benthic survey was carried out from November 1998 to December 1999 in the tidal flats of Bahía Samborombón (Río de la Plata estuary, Argentina), in order to study the population structure, growth and secondary production of Laeonereis culveri. The samples were collected monthly in two intertidal areas with different environmental characteristics (San Clemente Creek and Punta Rasa). Growth was analysed using computer-based methods of length–frequency data (ELEFAN), and the secondary production was estimated by Crisp's and Hynes & Coleman's methods. Laeonereis culveri were recruited throughout the year, with two main peaks during spring and autumn. The autumn cohort showed growth rate (K) of 2 in San Clemente Creek and 1.8 in Punta Rasa. The seasonal oscillation of growth pointed out that worms grow very slowly during winter months. The life span of this cohort ranged from 15 to 17 months. The spring cohort showed higher growth rates in both sampled areas (K=3.3 in Punta Rasa and 3.1 in San Clemente Creek), whereas the growth oscillation showed similar values to those of the autumn cohort. The lowest growth rate was found in January and the life span was 9.5 months. The annual mean biomass in San Clemente Creek was 5.44 g m−2, with a mean production of 40.8 and 43.8 g m−2 y−1, according to the method used, and a production/biomass (P/B) ratio of 7.5 and 8 y−1 respectively. In Punta Rasa, the annual mean biomass (2.69 g m−2) and mean secondary production (19.44 and 23.61 g m−2 y−1, according to the method used) were lower than in San Clemente Creek, nevertheless the P/B ratio (7.2 and 8.7 y−1) was similar. The high secondary production and P/B ratio observed suggest that L. culveri transfer an important biomass to higher trophic levels, pointing out the very important role that this polychaete plays in the energy flux of this coastal estuarine ecosystem.

1. The development of Scolecolepis fuliginosa (Claparède) is described from the egg to the young worm for the first time.

2. Comparison of reared larvæ with larvse from the plankton did not reveal any important difference.

3. The eggs are pelagic, and are similar to those of Nerine.

4. A description is given of the histological structure of a ciliated pit which arises in early larval existence and disappears at metamorphosis. The structure of the glandular region of the pygidium is also described.

5. It is apparent that from the attainment of the fourth setiger onwards, the centre of differentiation is located in the third setiger, so that segmental structures arise first in this segment and then appear in the first and second setigers as well as in the succeeding ones.

6. The larva of Scolecolepis has three pairs of eyes, the third pair disappearing in the young worm long after metamorphosis is otherwise complete.

Third-stage larval and adult infrapopulations of the whaleworm Anisakis simplex sensu lato (s.l.) (Nematoda: Anisakidae) from their respective fish, cephalopod and cetacean hosts caught or stranded in the Galician coast (north-west Spain), were analysed for heavy metals by atomic absorption spectrometry. Results suggest that the whaleworm may accumulate lead and copper to levels far in excess of their host tissues.

The variability of larval morphology in the caridean shrimp Nauticaris magellanica cultivated in the laboratory was analysed, and its applicability for the identification of larval stages collected from the plankton evaluated. Both morphometric and meristic variability of selected appendages was analysed comparing larvae from the rearing experiment with those obtained from the plankton. Larval development in the laboratory consisted of at least nine zoeal and five decapodid stages, followed by the first juvenile stage. Larvae collected from the plankton, comprising individuals from zoea II to, presumably, zoea VIII, were generally more developed and had a larger size than the corresponding stages reared in the laboratory. Cultured larvae showed a high exophenotypical variability starting with zoea IV, which impeded an immediate determination of larval stages obtained from the plankton.

While on shore-collecting expeditions in this district it was frequently observed that Echinus miliaris has the habit of associating together in pairs, and sometimes in groups of more than two. The association of these pairs and groups is sometimes so intimate that it is not possible to interpose even the blade of a penknife between the interlocking spines of the urchins. In all cases observed except one, such pairs were placed side by side, but in one particular case the apical region of one individual was almost certainly placed adjacent to the apical portion of the other. In all the collecting expeditions—made at various times of the year between April and August—on which groups were collected, the total number of urchins of all sizes obtained amounts to about 710. Among this number were obtained 84 groups, which amount in all to 189 specimens. In the earlier part of the investigation a group was taken as such if the members were merely fairly close together, but afterwards only those specimens were recorded which were actually touching one another in the manner described above. Out of the total of 84 groups only 27 were actually recorded definitely as touching one another, although some of the other groups may have been touching. Of these 27 closely associated forms all the individuals were ripe except 3 small specimens belonging to two pairs which were recorded as having an immature gonad. The remainder consisted of 19 pairs, 2 pairs, 1 pair, and 3 groups respectively.

Squid of the genus Alloteuthis from the Aegean Sea and eastern Mediterranean were identified as A. media. It is not possible to distinguish A. media from A. subulata by relative fin length. Both ‘species’ are probably intraspecific forms. Egg size varied from 1·5 to 2·3 mm. Oocyte maturation in the ovary occurs in batches. The potential fecundity is some 1000–4000 eggs, most of these being released during continuous spawning accompanied by female growth.

Methods used to identify individual organisms consistently over time have been invaluable tools in ecological studies, enabling reliable assessments of time-dependent parameters such as growth and mortality, and an accurate determination of their variance. These methods have proved to be particularly amenable to gastropods owing to the presence of an external shell on which marks or tags can be applied with little or no adverse effects on the animal. Marking and tagging techniques have enabled the study of several ecological parameters in adult marine gastropods, including growth (Frank, 1965; Hughes, 1972; Palmer, 1983; Gosselin & Bourget, 1989), mortality (Frank, 1965; Hughes, 1972), movements (Frank, 1965; Chapman, 1986), and foraging behaviour (Menge, 1974; Hughes et al., 1992). Small organisms, however, can pose considerable problems for individual marking (Southwood, 1978). As a result, marking and tagging methods have seldom been applied to newly hatched or recently settled juvenile marine gastropods. Several methods have been developed for simultaneously labelling large numbers of invertebrate larvae (Levin, 1990), and some of these methods may be applicable to juvenile gastropods. The usefulness of these methods, however, is limited because all animals receive the same label and, consequently, individual animals cannot be recognized. To my knowledge, no method of individually marking very small juvenile marine gastropods has been documented. In fact, it is sometimes perceived that small juveniles cannot be individually marked due to their small size and sensitivity (Frank, 1965; Palmer, 1990). The object of this paper is to present a simple method of marking early juvenile gastropods, which consists of applying colour codes to the shells of individuals as small as 0·9 mm in length.

Intertidal estuarine barnacles suffer cyclic changes in salinity and temperature, the latter being most marked and often quite abrupt at the time of tidal immersion and emersion.

Examining how variability in population abundance and distribution is allotted among different spatial scales can inform of processes that are likely to generate that variability. Results of studies dealing with scale issues in marine benthic communities suggest that variability is concentrated at small spatial scales (from tens of centimetres to few metres) and that spatial patterns of variation are consistent across ecosystems characterized by contrasting physical and biotic conditions, but this has not been formally tested. Here we quantified the variability in the distribution of intertidal rocky shore communities at a range of spatial scales, from tens of centimetres to thousands of kilometres, both in the NE Atlantic and the Mediterranean, and tested whether the observed patterns differed between the two basins. We focused on canopy-forming macroalgae and associated understorey assemblages in the low intertidal, and on the distribution of Patella limpets at mid intertidal levels. Our results highlight that patterns of spatial variation, at each scale investigated, were consistent between the Atlantic and the Mediterranean, suggesting that similar ecological processes operate in these regions. In contrast with former studies, variability in canopy cover, species richness and limpet abundance was equally distributed among spatial scales, possibly reflecting the fingerprint of multiple processes. Variability in community structure of low intertidal assemblages, instead, peaked at the largest scale, suggesting that oceanographic processes and climatic gradients may be important. We conclude that formal comparisons of variability across scales nested in contrasting systems are needed, before any generalization on patterns and processes can be made.

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 shell strengths of seven species of barnacle were investigated by carrying out a series of compression and tension experiments. All species were tested under compression as solitary individuals. In addition the shell strength of crowded Semibalanus balanoides was determined. Results of the compression experiments show Balanus balanus and B. perforatus to be the strongest species with Verruca stroemia the weakest. All species were much weaker in tension than compression, particularly those with a calcified base, B. balanus being the weakest of the five species tested in this way.

The possibility of adaptive design of the barnacle shell to withstand wave action and predation techniques is discussed in the light of the results from the compression and tension experiments. Finally the importance of carrying out a wide range of tests of the shells when trying to determine their strength is discussed.

The mud shrimps of Iran are not well known. Material for the present study was collected from 21 out of 51 intertidal localities from the Persian Gulf and Gulf of Oman, Iran. In total, 11 species were found along the Iranian coast. These were belonging to three families, including Upogebiidae (Upogebia carinicauda, U. darwinii and U. pseudochelata), Callianassidae (Neocallichirus jousseaumei, N. calmani, Callichirus masoomi, Corallianassa coutierei, Michaelcallianassa indica, Paratrypaea bouvieri and Gourretia coolibah) and Callianideidae (Callianidea typa). Geographical distributions of the species were considered and the results show that each species is totally dependent on a special type of habitat. Comparing different types of habitat, sandy and muddy substrates of the intertidal and shallow subtidal zone are found as the dominant habitat type for all species, but some species have a preference for boulder dominated coasts or occupy already existing holes and crevices in the boulder and bedrocks. In addition, the world distribution of each species was considered, and according to their present recorded localities, these are grouped into two distributional categories including the Indo-West Pacific region and one in a broader area of the Indo-Pacific.

1. Much of what was formerly considered to be phosphorus in organic combination, in sea-water, is in reality arsenic.

2. Certain analyses giving high values for phosphate in sea-water and a June minimum very far from complete exhaustion of phosphate are vitiated by the inclusion of arsenate, as arsenomolybdate, in the phosphomolybdate precipitate.

3. Arsenic in sea-water exists mainly in the form of arsenite. The arsenate present, if any, has hitherto been included in the results obtained for phosphate.

4. Since arsenic is found in algæ and has been recorded as increasing in quantity with increase of depth it seems that the arsenic present in sea-water must undergo seasonal changes.

A numerical model is used to derive the diurnal tides on the N.W. European Shelf. The quadratic friction term was linearized using both tidal and wind driven currents. The semidiurnal tidal currents essentially provide the friction for the diurnal tides except in a few relatively small regions (semidiurnal current amphidromes) and the Skagerrak where the wind driven currents dominate. Accurate M2 tidal currents are required for the diurnal bottom stress tensor and the M2 tidal current amplitudes are considered accurate to about 95%. Some discrepancies between model energy M2 dissipation rates and some observed estimates reported for the English Channel and Celtic Sea regions were noted.

Balaniger balticus gen. et sp.nov. (Prymnesiophyceae) is described on the basis of electron microscopy of shadow-cast whole mounts, prepared from water samples collected in October 1975 at localities in the western Baltic. The saddle-shaped cell has two smooth flagella and a short haptonema. The cell surface is covered with oval organic scales supporting calcified pyramid-like structures. Confirmation of the calcification of the periplast has been achieved by applying an X-ray analytical electron probe to one of the specimens observed.