Reproductive cycles are determined from samples taken at regular intervals over a period of time related to the assumed periodicity of the breeding cycle. Fiscal, ship time and sampling constraints have made this almost impossible at deep-sea vents and seeps, but there is an accumulating mass of data that cast light on these processes. It is becoming apparent that most reproductive processes are phylogenetically conservative, even in extreme vent and seep habitats. Reproductive patterns of species occurring at vents and seeps are not dissimilar to those of species from the same phyla found in non-chemosynthetic environments. The demographic structure of most vent and seep animals is undescribed and the maximum ages and growth rates are not known. We know little about how the gametogenic cycle is initiated, though there is a growing body of data on the size at first reproduction. Gametogenic biology has been described from seasonal samples for only one organism from vent/seep environments. For other species, the pattern of gametogenesis has been described from serendipitous samples that allow determination of reproductive effort, but such samples reveal little about energy partitioning during the gametogenic process. Some notable adaptations have been described in mature gametes, including modified sperm. Spawning has been observed for a number of species both in situ and in vitro. Knowledge of the larvae of vent/seep organisms has been derived from laboratory fertilizations, from field collections over vent and seep areas and, for molluscs, from protoconch or prodissoconch size and shape. Larval dispersal has been perhaps the most intractable aspect of reproduction. Because the length of larval life is known for only a single seep organism and no vent organism, we cannot infer dispersal distance from a knowledge of current velocities. Modelling has been used to assess the maximum larval distance that allows effective migration between vent sectors. An indirect approach has been to estimate gene flow within, and between, vent sites using DNA sequencing and electrophoretic techniques. Although data are still equivocal, there are indications of considerable mixing among populations within and between vent sectors of the same ridge. Our knowledge of reproductive biology in vent and seep organisms remains fragmentary, but with molecular and biochemical techniques, emerging larval culture techniques, and increased sampling effort, the pieces of the jigsaw will eventually form an overall picture.

The position and structure of the North Atlantic Subtropical Front is studied using Lagrangian flow tracks and remote sensing (AVHRR imagery: TOPEX/POSEIDON altimetry: SeaWiFS) in a broad region (∼31° to ∼36°N) of marked gradient of dynamic height (Azores Current) that extends from the Mid-Atlantic Ridge (MAR), near ∼40°W, to the Eastern Boundary (∼10°W). Drogued Argos buoy and ALACE tracks are superposed on infrared satellite images in the Subtropical Front region. Cold (cyclonic) structures, called ‘Storms’, and warm (anticyclonic) structures of 100–300 km in size can be found on the south side of the Subtropical Front outcrop, which has a temperature contrast of about 1°C that can be followed for ∼2500 km near 35°N. Warmer water adjacent to the outcrop is flowing eastward (Azores Current) but some warm water is returned westward about 300 km to the south (southern Counterflow). Estimates of horizontal diffusion in a Storm (D=2.2×102 m2 s−1) and in the Subtropical Front region near 200 m depth (Dx=1.3×104 m2 s−1, Dy=2.6×103 m2 s−1) are made from the Lagrangian tracks. Altimeter and in situ measurements show that Storms track westwards. Storms are separated by about 510 km and move westward at 2.7 km d−1. Remote sensing reveals that some initial structures start evolving as far east as 23°W but are more organized near 29°W and therefore Storms are about 1 year old when they reach the MAR (having travelled a distance of 1000 km). Structure and seasonality in SeaWiFS data in the region is examined.

The scavenging fauna of the Patagonian slope (900–1750 m), east of the Falkland Islands was investigated using the Aberdeen University Deep Ocean Submersible (AUDOS), an autonomous baited camera vehicle designed to photograph scavenging fish and invertebrates. The AUDOS was deployed on ten occasions in Falkland waters. Nine experiments were of 10–14 h duration and baited with 800 g of squid and one experiment lasted six days, baited with a 10 kg toothfish (Dissostichus eleginoides). Analysis of photographs revealed considerable patchiness in the composition of the scavenging fauna. Hagfish (Myxine cf. fernholmi) dominated three of the shallower experiments including the 6-d experiment, arriving quickly from down-current, holding station at the bait and consuming the soft tissues first, with consumption rates of up to 200 g h−1. In the other experiments, stone crabs (Lithodidae), the blue-hake (Antimora rostrata) and amphipods were the primary consumers, but the rate of bait consumption was lower. Patagonian toothfish (D. eleginoides) were attracted to the bait at each experiment, but did not attempt to consume the bait. The patchiness in the fauna may be a result of depth, substratum and topography, but in general the rapid response of the scavenging fauna indicates that carrion is rapidly dispersed, with little impact on the local sediment community.

In a preliminary study of the marine benthos of Ría de Ares-Betanzos, 50 stations covering the quadrant delineated by the coordinates 43°26′42″N–43°20′42″N and 08°18′54″W–08°10′12″W were sampled and sediment samples analysed for particle-size composition, sand, silt and clay content, degree of sorting, median diameter and grain-size diversity of sediments. Organic and inorganic content, total carbon and nitrogen, carbonates, organic carbon/total nitrogen ratio and bathymetric data were also collected. On a smaller scale a few stations were sampled for sediment redox potential and pH measurement. The salinity, temperature and oxygen content of the overlying water was also assessed.

Cluster analysis and Principal Component Analysis methods were used to describe seabed heterogeneity and the pattern of sediment distribution within the ría, and to relate the environmental variables to each sediment type. Sediments were predominantly fine to very fine sands, and exhibited a direct depth-related gradient, i.e. with the finer grades, higher organic carbon and silt and clay occurring at the shallower areas of Pontedeume, Ares and Redes inlets and Ría de Betanzos sector where terrigenous input was important. Carbonate, organic carbon and organic matter maxima occurred in the central sector of the ría where most mollusc recruitment takes place: revealing the chiefly bioclastic origin of sediments. Taking into account the geological and hydrographic processes, explanations for the formation of the sedimentary bottoms in Ría de Ares-Betanzos are provided.

Callista chione is the most prominent suspension-feeding bivalve species inhabiting the soft bottoms of the Bay of Banyuls-sur-Mer. Ingestion rates and absorption efficiencies when fed monospecific cultures of either phytoplankton (Pavlova lutheri) or bacteria (one natural strain isolated from the marine environment) were determined using 14C radioactive pulse–chase feeding experiments. Microalgae were ingested at a rate five to six times higher than bacteria (i.e. 2.31×10−3 against 0.40×10−3 mg DW mg SFDW−1 h−1). Such differences were attributed to differences in average particle sizes. Bacteria were also less absorbed than microalgae (i.e. 64.3 vs 83.8%). Together with existing data regarding the ratio of free to attached bacteria in the oceanographic environment, these results suggest that free bacteria probably contribute to meet only a small portion of the energy requirements of adult C. chione populations.

The assemblages of attached and freeliving epibenthic species in the North Sea are described, based on analysis of samples collected with a small beam trawl. Clustering of survey sites based on the presence or absence of attached species indicated that three regions had characteristic assemblages: the northern North Sea, the central North Sea from 55 to 57°N and the southern North Sea. Clustering of sites based on counts of free-living epibenthic species also revealed that the sites formed three major groups but these corresponded to regions in the north-east North Sea, the northern and western central North Sea and the southern and eastern central North Sea. Species which contributed most to the similarity within and dissimilarity between groups were identified. The environmental factors which best accounted for the grouping of sites were depth, winter temperature and the temperature difference between winter and summer for attached species and depth and the temperature difference between winter and summer for free-living species. The species richness of attached and free-living epibenthic species was higher in the central and northern North Sea than in the south. The number of abundant (Hill's N1) and very abundant (Hill's N2) free-living species also increased from south to north.

To estimate the importance of the vertical daily migrations in the structure of the community of the epifauna associated with the leaf stratum of Posidonia oceanica, we compared to the vagil epifauna abundance in respect to the period of the day and the height of the sediment. The study was developed in the P. oceanica meadow of El Campello (Alicante, south-east Spain), during May of 1996, to a depth of 12 m, repeating the samplings in four sites to obtain a correct spatial interpretation. Three main behaviours were detected. Decapods, amphipods, isopods, mysids, ostracods and polychaetes showed a nocturnal increase in the leaf stratum of P. oceanica. By contrast, copepods showed a nocturnal decrease in the leaves and gastropods did not show any temporal change. Chaetognaths and acari did not show statistical differences because of the considerable spatial heterogeneity. These vertical migrations have an extreme importance in the configuration of the structure of the epifauna associated to P. oceanica, in addition to the diverse response of the different taxa.

During 1996–1997 a systematic sampling programme was carried out in brackish coastal lakes and lagoons and in the delta of the River Po. In six of the nine collecting locations, 12 species of Gastrotricha were identified. One species, Chaetonotus ichthydioides, is new to science; another three species, the chaetonotidans Heterolepidoderma foliatum and the macrodasyidans Dendrodasys ponticus and Turbanella cf. pontica, and one macrodasyidan genus, Paradasys (P. subterraneus), were found in Italy for the first time. The unusual morphology of some of the species identified shows that Gastrotricha colonized brackish waters from both marine and freshwater habitats.

The putative impact of subsistence foragers along the Transkei coast of South Africa was determined by comparing the community-level attributes of infratidal macrofaunal assemblages in three ‘no-take’ reserves with those at adjacent exploited localities. The objective of this study was to ascertain whether the differences in the assemblages found at exploited and non-exploited localities were consistent along this coast. Two-way ANOVAs indicated that the presence/absence of exploitation had no effect on univariate community measures. Macrofaunal biomass was the only measure which showed significant differences amongst locations and interaction effects. Abundance/biomass comparison curves revealed that all the exploited sites except one showed the configuration typical of moderately disturbed sites and that all the non-exploited sites except one showed the trend typical of undisturbed sites. Two-way crossed ANOSIM tests indicated that treatment and location both had significant effects on these assemblages and that there were also significant differences between each pair of locations. The latter probably reflects regional differences in species composition due to the fact that this coast lies at the junction of two zoogeographic marine provinces. The multidimensional scaling (MDS) ordinations derived from abundance and biomass estimates revealed two major clusters of sites, one representing sites in the southern region and the other sites within the central and northern regions. The non-exploited sites within each region were situated above and to the right of the corresponding exploited sites. Similarity percentage analyses (SIMPER) indicated that the major species contributing to the average dissimilarity between the exploited and non-exploited localities varied regionally. There was, however, a fair amount of consistency in terms of the functional groups highlighted by these analyses. Some of the species adversely affected by exploitation are dependent on primary substrata either for their food supplies or for attachment. Likewise many of the species which appeared to benefit from exploitation were phytal-associated forms.

Polar benthic communities are subject to a range of disturbance levels from a variety of sources, principal amongst which is ice. This occurs in four main forms: the ice-foot, ice scour, anchor ice and fast ice, each of which influences benthos in a very different temporal and spatial manner. The four described forms of ice disturbance are all seasonal, but combined, influence communities throughout the year. The magnitude of ice mediated disturbance is often catastrophic and as a result both dominates benthic community structure and makes recolonization and development rates critical. This disturbance extremity results in high temporal and spatial heterogeneity, very low intertidal zone diversity and in places low mid–sublittoral diversity. It may also, however, be important in generating and maintaining the typically high sublittoral zone diversity observed at many polar localities. Intermediate frequencies or magnitudes of disturbance have been controversially discussed as important in maintaining diversity by prevention of space monopolization by overgrowth dominants in such environments as the deep sea. The shelf areas examined to date certainly suggest intermediate disturbance is important in maintaining polar sublittoral zone diversity. The combination of slow colonization and development with high frequencies of disturbance means most polar nearshore environments that have been described are permanently in a state of change or recovery.

The estuary of the River Crouch, south-east England, as sampled annually by beam trawl between 1987 and 1989, and again in 1992. The aim of an initial transect survey was to describe and quantify the subtidal epifauna at a time of high ambient tributyltin (TBT) concentrations, arising from the use of tin-based anti-fouling paints on the hulls of moored pleasure craft. Subsequent surveys at representative stations sought to examine the progress of any changes with time in animal populations in relation to a decline in concentrations of TBT in the environment, following a ban on the use of tin-based paints for smaller vessels in July 1987.

Species body size spectra have been constructed for macrofauna assemblages from four sites with contrasting sediment granulometry and heterogeneity in and around Plymouth Sound. The number of species and species turnover (β diversity) were higher on coarse sediment. While the fauna were distinct between sites, the median geometric size-class was conservative (class 14; 0.153–0.305 mg dry blotted weight). Only one site had significantly lower heterogeneity within the species size spectrum, yet this was the most heterogeneous sediment. As such, we were unable to reject the null hypothesis that species body size distribution patterns are conservative despite differences in sediment granulometry and heterogeneity.

Located at 22°N on the northern shore of the South China Sea, Hong Kong experiences a seasonal, monsoonal climate and its resident scleractinian corals, comprising some 50 species, live here at the limit of their ranges. Summers are hot and wet, winters cold and dry and this study was initiated to determine the effects of bioerosion and periodic episodes of strong wave action on coral death and beaching. Coral rubble washed up on Telecom Bay Beach in the Cape d'Aguilar Marine Reserve was collected every month from January 1996 until December 1997, inclusive. Quantities were greatest after typhoons and storms, with the average monthly weight of recently-living corals accounting for approximately 0.007%, by weight, of the total live coral in the bay. Seventeen species of Mollusca were recorded from within the skeletons of this rubble and included a new record for Hong Kong, Anchomasa yoshimurai (Pholadidae). Species of Lithophaga dominated, with highest mean abundances recorded from within Goniastrea aspera, the most abundant living coral in the bay and from within the heaviest fragments. The overall incidence of borers was, however, low although it appears that dead coral borers, notably the basally boring Lithophaga lima, act to weaken coral attachment resulting in dislodgement and beaching during and after storms. At this relatively unperturbated site, therefore, the significance of borers in weakening coral attachment with subsequent detachment and beaching during and after storms, respectively, is low, a situation also seen elsewhere.

Divisional morphogenesis of the marine hypotrichous ciliate, Tachysoma ovata was investigated based on protargol impregnated specimens. Its morphogenesis reveals the following peculiarities: (1) there is a definite period during which the anterior part of the newly formed adoral zone of membranelles (AZM) in the opisthe connects with the parental AZM which remains unchanged during the morphogenesis. (2) The anlagen of left and right marginal rows do not develop simultaneously. (3) The replication processes of macronuclear segments are not recognizable during cell division. It is likely that the replication takes place during the interphase. (4) The origin of the fronto-ventral-transverse (FVT) cirral anlagen in the opisthe is characteristic: in other Tachysoma spp. these primordia are generated either from differentiated parental ciliatures (or are orientated by pre-existent organelles), or by division of the proter's FVT-cirral primordia. (5) The primordium of the undulating membranes in the proter always keeps the form of two streaks (so-called ‘semi-anlagen’). There is no conspicuous dedifferentiation or reorganization of the undulating membranes. A morphogenetic comparison with other species of this genus was carried out.

Fieldwork on the estuary of the River Crouch in Essex between 1987 (when the use of TBT antifouling on boats less than 25 m in length was banned) and 1992 revealed marked increases in the species diversity of sublittoral benthic communities in the areas which had originally been most contaminated with TBT. These increases were mirrored by a decrease in the TBT contamination of the sediments. The bivalve molluscs and amphipod crustaceans showed the most marked increases in abundance and diversity.

The pattern of occurrence of medusae off the north-east coast of England are described for the period 1990–1996. The predatory role of the medusae, Aglantha digitale, was examined by comparison of estimated predation rates with those of other planktonic predators. Aglanthe digitale was found to have the potential to considerably reduce copepod abundances, particularly in winter. Other important predators were the amphipod Themisto compressa and the chaetognath Sagitta elegans. There was a great deal of seasonal and interannual variability in predatory impact, with predators such as Pleurobrachia pileus and Meganyctiphanes norvegica occasionally exerting a high predatory impact. Previous studies have identified an important community structuring role for predation in winter in this area, this study shows that planktonic predators can influence copepod abundances throughout the year.

In order to estimate the degree of implantation of excavating sponges in the oyster populations from the littoral zone at Blanes (north-western Mediterranean Sea), a representative sample of oysters (Ostrea edulis) was collected from depths between 0.5 and 4 m in 1986. All oysters were infested by the excavating sponges Cliona viridis and Cliona celata. Infestation affected always and exclusively the lower valve always reaching the inner side. The degree of infestation proved to be independent of oyster size and weight. Colonization by contact was considered the main means of dispersion of these sponges within the oyster population. Cliona viridis and C. celata emerged as the single excavating species able to effectively compete with other non-excavating or excavating organisms when trying to colonize the particular calcareous substrate provided by oyster shells in the north-western Mediterranean Sea.

A small collection of horny sponges from the north-eastern coast of Papua New Guinea is recorded. It consists of 19 specimens belonging to ten species, of which three are new: Thorectaxia papuensis, Chelonaplysilla delicata, Anomoianthella lamella. Thorectaxia is proposed as a new genus in the family Thorectidae.

A morphological, cytological and genetic comparison of putative conspecific populations of Spirastrella sp. cf. mollis (Porifera: Demospongiae) from both sides of the Isthmus of Panama revealed a very high level of genetic differentiation together with morphological and cytological differences. The main differences were the distribution of the spirasters within the choanosome, the size and shape of spirasters 1, and the size and shape of inclusions within type I cells. Consequently these two populations clearly belong to different biological species. The Atlantic one, S. hartmani sp. nov. corresponds to what previous authors have called S. cunctatrix in the Caribbean. The finding of this new species raises to three the number of Spirastrella spp. known from the Caribbean Sea. The Pacific species is named here S. sabogae sp. nov. The levels of gene divergence found between S. hartmani and S. sabogae (Nei's genetic distance D=2.30) were as high as those found between different genera in other groups of invertebrates. Similarly exceptionally high values of gene divergence have been found between other congeneric sponge species and may be indicative either of a higher rate of molecular evolution or a very slow rate of morphological evolution in the Porifera compared to other metazoans.

Meio- and macrofauna density and biomass were estimated at the OMEX-transect across the continental slope of the Goban Spur at water depths ranging from 208 to 4460 m in the north-east Atlantic. A linear increase in the ratio between meio- and macrofauna densities with increasing water depth was found. At the continental shelf meiofauna densities were ∼50 times higher than macrofauna densities, whereas in the abyss meiofauna densities were more than 1000 times higher. This change in ratio was due to a significant decrease in macrofauna densities with increasing water depth, whereas the meiofauna densities stayed more or less at the same level. The ratio in biomass between meio- and macrofauna showed a dip at ∼1000 m. At this depth macrofauna biomass was ∼55 times higher than meiofauna biomass, whereas at ∼4500 m macrofauna biomass was only about three times higher. Macrofauna biomass was high at ∼1000 m, due to the high mean individual weight of the macrofauna, whereas meiofauna biomass and mean individual weight were low at this depth.

Meiofauna consisted of ∼90% nematodes. Within the macrofaunal fraction (>0.5 mm) a linear increase in the ratio between nematodes and macrofauna sensu stricto with depth was found. At the deepest station ∼20% of the macrofaunal fraction were nematodes, at the shallowest station only ∼2%. Thus, large nematodes became relatively more important with increasing water depth. Within the macrofauna a decrease in the abundance of filter- and surface deposit-feeders relative to the subsurface deposit-feeders with increasing water depth was observed, which may be related to a change in food input. As no decrease in mean individual weight with increasing water depth within either group could be observed, the change in meio:macrofauna ratios along the OMEX-transect merely reflects a change in taxonomic (functional) composition, rather than a change in size.