Ashadze-1 (12° 58′N 44° 51′W, 4080 m) on the Mid-Atlantic Ridge (MAR) is the deepest known active hydrothermal vent field. The first observations on this site were numerous clear and black smokers and surprisingly few known symbiotic species dominant in other vent areas on the MAR. The species most abundant at Ashadze-1 are those usually found at the periphery of hydrothermal communities: sea-anemones Maractis rimicarivora and chaetopterid polychaetes Phyllochaetopterus sp. nov. This study comprised site mapping and faunal sampling and Ashadze-1 was completely mapped by using the remote operated vehicle ‘Victor 6000’ and a new high resolution tool available for deep-sea research. A photo-mapping survey was carried out with a long range optical black and white camera. Digitization of substrata and sea-anemones visible on the images was performed by GIS. Spatial distribution of Ma. rimicarivora was distinguished by high densities of 32 ind.m−2 on the western side of the main smoker area. Submersible sampling operations allowed taxonomic identification within a 200 × 110 m area. Carbon, nitrogen and sulphur isotopic ratios were measured in four dominant species to identify their trophic position. The present paper gives the complete maps and describes the faunal community of the Ashadze-1 vent field. The results obtained led us to consider this site as an ecosystem in its declining stage. Finally we compare the similarities of this community to other hydrothermal communities on the northern MAR.

Despite the importance of early life-history processes in regulating population assemblages of benthic invertebrates at hydrothermal vents, they remain poorly understood, mainly because of the inaccessibility of these habitats. Vestimentiferan tubeworms provide an excellent system to study settlement in these habitats; they inhabit tubes that remain intact for some period even after the occupants die, and thus provide a proxy for rates of settlement and post-settlement mortality. In 2007, we collected rocks supporting populations of Lamellibrachia sp. using a TV-grab, from Mussel Ridge hydrothermal vent field on Monowai Volcanic Complex, at the Tonga–Kermadec arc. Twenty-two discrete patches of similarly sized individuals and of discrete length–frequency distributions were identified and quantified. Mean length of individual tubeworms ranged from <0.5 to 6.38 cm, and abundance per patch ranged from 6.8 to 108 ind cm−2. Post-settlement mortality was ~5%. These results suggest that gregarious settlement of pulses of larvae is likely occurring by Lamellibrachia sp., a process that has not yet been described in deep-sea hydrothermal vent tubeworms. The abundance of adult tubeworms on Monowai was low, and allochthonous larval supply from neighbouring seamounts unlikely. Consequently, gregarious settlement can increase the probability of maintenance and expansion of the existing populations.

The galatheid crab Shinkaia crosnieri, is the sole member of the subfamily Shinkaiinae. It is abundant and forms dense beds around active hydrothermal vents in the Okinawa Trough. Thousands of filamentous bacteria attached to the plumose setae on the ventral surface of this crab were observed using field-emission scanning electron microscopy and transmission electron microscopy. Nucleic acids were extracted from the filamentous bacteria, and the phylotypes of 16S rRNA genes were identified from 81 clones. These phylotypes were divided into three groups: Epsilonproteobacteria (74%); Gammaproteobacteria (20%); and Bacteroidetes (6%). Gamma- and major phylotypes of Epsilonproteobacteria were also detected using fluorescence in situ hybridization analysis. These Epsilon- and Gammaproteobacteria were closely related to cultured and uncultured bacteria from hydrothermal vent fields including episymbionts of vent-associated invertebrates such as Rimicaris exoculata, Alvinella pompejana, the scaly-foot snail, Kiwa hirsuta etc. The carbon isotopic compositions of the muscle of S. crosnieri and in filamentous bacteria were similar. The muscle of S. crosnieri contained monounsaturated C16 and C18 fatty acids, which are known to be characteristic of sulphur-oxidizing bacteria in H2S-rich marine habitats. Through the video images transmitted by a submersible and a remotely operated vehicle, S. crosnieri was observed to comb out its ventral setae using the third maxilliped and appeared to consume the contents. These evidences suggest the epibiotic association between S. crosnieri and the filamentous bacteria attached to the ventral setae of the crab, but the details of role and function are still unclear at the present study.

The study focuses on the question, how a seamount in the oligotrophic eastern Mediterranean affects the zooplankton community, as compared to the open water. Zooplankton samples were taken with 333 µm nets at two sites, the Rhodes Basin and the Anaximenes Mountain, in December 2006. The samples were sieved into size fractions, and the composition, biomass, abundance and stable isotope signatures were analysed. In general, biomass and abundance of zooplankton were low, reflecting the oligotrophic character of the eastern Mediterranean, but zooplankton standing stocks were higher at the Rhodes Basin than at the Anaximenes Mountain. Stable isotope signatures showed, at a generally low level, enrichment in zooplankton taxa along the food chain within the different pelagic zones and from the surface to the deep-sea, but no significant differences between Rhodes Basin and the seamount were evident in the food web structure. The zooplankton community in the Anaximenes Mountain region in the northern Levantine Basin seems not to be influenced by a local seamount effect, despite the difference in standing stocks between the seamount and the Rhodes Basin. This seems to be driven by larger-scale upwelling and downwelling structures of cyclones and anticyclones, dominating the circulation in the area.

The north-eastern Aegean Sea (NEA) is a marine system of high hydrological complexity, principally induced by the inflow and subsequent advection of the low salinity (<30) Black Sea water (BSW). This water mass occupies the upper layer (~0–20 m) of the NEA and plays a key role in the determination of circulation patterns and the generation of various frontal and eddy structures. Here we are concerned with the examination of mesozooplankton assemblages in the NEA during the thermal stratification period (July 2004) in two discrete sampling layers: (a) Layer 1 (from the base of halocline to the surface: ~0–20 m) which is directly influenced by BSW; and (b) the deeper ~20–50 m layer (Layer 2). Our main objective was to assess the response of mesozooplankton to the BSW and the associated hydrological structures. In July 2004, the BSW was mainly restricted in the eastern part of the NEA where it was entrapped in a ~50-km wide anticyclonic gyre (Samothraki gyre). A marked spatial differentiation in mesozooplankton assemblage structure, significantly related to this hydrodynamic partitioning, was detected in Layer 1. Sampling sites under the direct influence of low salinity–high temperature gyre waters were characterized by a considerably higher mesozooplankton stock than the remaining area, mainly due to the outstanding numerical dominance of the cladoceran species Penilia avirostris. Copepods displayed notably low densities within the gyre and low species diversity, the calanoid Temora stylifera was the only abundant species. The mesozooplankton community outside the gyre zone shifted towards lower levels of total abundance, with a lesser contribution of cladocerans and an increase in the importance of small-sized copepods (e.g. Acartia clausi, Paracalanus parvus, copepodites of Oithona spp. and Clausocalanus spp.). In the subsurface layer (Layer 2), the mesozooplankton community also exhibited spatial heterogeneity which could be hardly explained by variability in environmental parameters. The periphery of the anticyclone below the halocline was distinguished from the remaining neritic area, presenting markedly high mesozooplankton productivity and distinct group composition. An inverse pattern in the mesozooplankton stock vertical distribution was observed at the periphery of the gyre (Layer 2> Layer 1) comparative to the remaining sites (Layer 1 > Layer 2), which was mainly due to unusually high concentrations of surface-living zooplankters below the halocline. The latter could be explained in terms of expected water flow patterns in an anticyclonic eddy.

This work focuses on the species associations of the Baronie Seamount (north-eastern Sardinia, Italy), according to variations in depth and time of day. The aim was to highlight the potential vertical movements of the species and to compare these results to existing data from a submarine canyon. Twenty-two samples were taken at different depths and times along two trawl lines over the seamount. A total of 94 species were caught; among these, 48 bony fish, 9 cartilaginous fish, 13 molluscs and 24 crustaceans were selected for analysis. Cluster analysis showed 3 groups in which both depth and time of day play an important role in grouping. Nine species showed some daily and nocturnal movement, probably linked to trophic requirements. The daily movements according to size and sex of the shrimps Aristaeomorpha foliacea and Aristeus antennatus were also studied. For these two populations, the analysis showed an uneven distribution and the diel cycle appears to involve only the females. These species seem to adapt their life cycle to the geomorphology of the sea bottom. The diurnal movements from the base of the seamount to the edge of the continental shelf increase the range of the species distribution. In fact, the seamount, due to its geomorphological conformation, offers these species the opportunity to very quickly span a considerable range of depths. These movements are known to occur in the continental shelf and slope, but in the seamount they are broadened and can be studied more easily.

In the context of the limited information on the ecology of port communities, the present work aims at assessing the small-scale spatial variability of zoobenthos inhabiting hard and soft substrata, in a Mediterranean port with high levels of commercial shipment. Samples were collected in summer from three stations and four depth levels, using core and quadrate samplers. A total of 34,578 individuals were collected, identified to 118 animal species. Soft substratum communities were impoverished and their structure varied spatially according to sediment composition. At a functional level deposit feeders dominated; their abundance decreased at the silty sites. Biotic indices were found inadequate for the assessment of ecological quality, due to the very low abundance of the fauna. Fouling communities varied spatially in vertical scales; diversity indices and the abundance of Bivalvia varied also in horizontal scales. Suspension and deposit feeders dominated showing a decreasing trend with depth. Two animal-dominated communities, serpulid blocks in the lower midlittoral zone and mussel beds in the sublittoral, substituted an algal-dominated community, which has been previously recorded from the same port quays. This substitution may be due to the intensive mussel farming in the nearby area contributing to the rapid expansion of mussels and of their serpulid biofoulers. Despite the existence of biogenic substrata, which enhance habitat complexity, the diversity of the associated fauna decreased and most species were tolerant to organic pollution. Recursive biomonitoring seems necessary to assess the ecological status of communities and to develop integrated management plans for temperate ports.

Taxonomic diversity and temporal patterns in abundance of periphytic ciliate communities across taxonomic levels were studied to monitor water quality in Korean coastal waters during April 2007. Specifically we compared two methods based on an artificial substrate (glass slide): the polyurethane foam enveloped slide (PFES) and the conventional slide (CS) systems. The results demonstrated that: (1) the colonization patterns of the ciliate communities at all taxonomic levels showed a lower variability in the PFES system than those of the CS system; (2) The taxonomic diversity (Δ) and taxonomic distinctness (Δ*) were significantly higher in the PFES system than those in the CS system; and (3) all four taxonomic diversity/distinctness indices represented lower variability in the PFES system than those of the CS samples. These findings suggest that the PFES system is more effective than the CS system for measuring the colonization patterns and taxonomic distinctness parameters that are increasingly used as potential indicators of water quality. This conclusion supports our previous suggestion that the PFES system is a better tool than the CS system for monitoring water quality in the marine ecosystem, using periphytic ciliates.

To reveal the annual patterns of planktonic ciliate communities, planktonic ciliate species composition, abundance and biomass, and responses to environmental conditions, were investigated during an annual cycle in Jiaozhou Bay, Qingdao, northern China. A total of 64 species belonging to five orders (Oligotrichida, Haptorida, Cyrtophorida, Hypotrichida and Tintinnida) were identified, 9 of which were dominant. Ciliate communities presented a clear seasonal pattern in terms of both abundance and biomass. A single peak of ciliate abundance and biomass occurred in late August, mainly due to the oligotrichids, tintinnids and haptorids. The 9 dominant species showed a distinct temporal distribution with seasonal successions of ciliate communities. Multivariate analyses revealed that ciliate abundance was significantly correlated with water temperature, dissolved oxygen and nutrients, especially nitrate nitrogen and soluble reactive phosphate (P < 0.05). These findings provided basic data on annual cycle of planktonic ciliate communities in a semi-enclosed bay of Yellow Sea, northern China.

The dominant intertidal algal species from Tarifa Island, Strait of Gibraltar, together with the associated peracarid crustacean community, were studied over a two-year period (December 2005–December 2007). Gelidium corneum and Gymnogongrus patens were dominant at the lower levels, close to the subtidal. Valonia utricularis, Osmundea pinnatifida, a turf of Caulacanthus ustulatus and Gelidium spp., Corallina elongata and Jania rubens were distributed in intermediate levels, while Ulva rigida, Chaetomorpha aerea and Fucus spiralis were collected from upper levels. The main intertidal seaweeds of Tarifa Island showed a perennial behaviour, but maximum values of biomass were registered during late spring and beginning of summer for most of species while the highest seawater temperatures were measured in late summer and beginning of autumn. Corallina elongata and Jania rubens, the dominant species which shared a niche at platforms of intermediate levels, showed an opposite behaviour, probably to avoid competence: C. elongata showed higher biomass in April–June and lower values in August–October–December, while biomass of J. rubens was higher in December–February and lower in April–August. Associated crustaceans, including mainly amphipods (gammarids and caprellids) were also present throughout the whole year with similar seasonality to seaweeds. However, crustacean density in the intertidal was not only influenced by distribution of algae as substrate, but also by external factors, such as hydrodynamism, oxygen, weather conditions, competition or predation. The present study constitutes the first baseline study dealing with seasonal fluctuations of algae and associated crustaceans in a protected area of the Strait of Gibraltar, an important biogeographical zone between Europe and Africa and the Mediterranean and Atlantic.

The invasive species Caulerpa racemosa var. cylindracea represents a serious threat to the diversity of benthic assemblages in the Mediterranean Sea. In the present study, a removal experiment was carried out to test whether, after 18 months of C. racemosa var. cylindracea exclusion, the macrophyte assemblage resembled a non-invaded assemblage. The results show that in the assemblage invaded by C. racemosa var. cylindracea the number of species, macrophyte cover, Shannon diversity and Pielou's evenness were lower than in the non-invaded assemblage. Erect perennial species were particularly affected and other introduced species were significantly reduced or completely excluded. After 18 months of removal/exclusion of C. racemosa var. cylindracea, only partial recovery of the macrophyte assemblage could be observed. Species numbers, total cover and erect perennial species cover were still significantly lower than in the non-invaded plots. However Shannon diversity and Pielou's evenness had reached comparable levels. In contrast to native macrophytes, the total cover of other introduced species reached a level comparable to the non-invaded plots. In summary, the present study revealed that after 18 months of C. racemosa var. cylindracea exclusion: (i) only partial recovery of the macrophyte assemblage occurred; and (ii) the development of other invasive species was favoured by the absence of C. racemosa var. cylindracea (Sisyphus effect).

The spatial distribution of the subtidal crustacean assemblages of the Guadiana River estuary was studied previous to the building of the Alqueva Dam (the biggest dam in Europe). The differences between an estuarine and marine environment seem to be the main reason responsible for the composition and distribution of the crustaceans along the study zone. The Guadiana estuary has shown high number of species in comparison with other nearby estuaries and this richness seems justified by the scarce influence of pollutants (most of them have shown low or moderate values) and their hydrodynamic and granulometric characteristics (76 species were found, 39 in the estuarine area). A gradient of enrichment and structuring of the assemblages was shown from the upstream to the marine zones and a spatial segregation of species was found along this estuarine environmental gradient, e.g. the amphipod Corophium multisetosum and the isopod Cyathura carinata in the upper estuary; the amphipod Bathyporeia cf. pilosa and the isopods Lekanesphera levii and Saduriella losadoi in the middle estuary; the amphipod Melita hergensis in the mouth; and a high number of species in the marine area. Since the Alqueva Dam will reduce the river discharges and may cause changes in the abiotic characteristics such as granulometry of sediments or salinity, this study establishes a baseline against which a monitoring programme or follow-up studies could measure any significant effects of the dam or related impacts.

Cadmium, chromium, copper, nickel, lead and zinc concentrations in the bivalve mollusc Macoma balthica and the polychaete annelids Hediste diversicolor and Arenicola marina were measured, during winter and summer, at sites throughout the Severn Estuary and Bristol Channel. The mean concentration of each metal in A. marina was greater in the lower Severn Estuary than in the far less contaminated outer Bristol Channel and the concentration of a given metal, e.g. Cr, in a species occasionally peaked at a site, reflecting local metal contamination. The concentrations of each metal in each of these biomonitor species almost invariably differed significantly among sites and often seasons and there were sometimes interactions between site and season. This indicates that the various factors that determine the concentration of a metal in a species operate in a complex manner and that their individual effects can vary among sites and/or seasons. The rank order of each metal concentration in each species at a site within the estuary frequently did not match the sequence for the concentration of that metal measured in the sediment at that site at the same time. This lack of correspondence is likely to be due, at least in part, to one or both of the following: (1) variations in the bioavailability of certain metals among sites due to differences in such features as the metal-binding properties of the sediments; (2) the effects of the constant transport and redistribution of the sediments and thus also of their associated trace metals by the very strong tidal action that characterizes the Severn Estuary. This would mean that single time measurements do not accurately reflect the overall trace metal environment to which the biomonitor organism had been exposed in the weeks/months prior to sampling. Marked differences in the concentrations of certain metals, e.g. Cu and Zn, in co-occurring biomarker species could frequently be related to differences between the ability of these species to regulate certain metals. Non-metric multi-dimensional scaling ordination and associated tests emphasize that the relationships between the concentrations of the various metals differed markedly among species and between sites and seasons in individual species and elucidated which metals contributed most to those differences. If the proposed scheme for harnessing tidal power in the Severn Estuary proceeds, the data in this paper provide a baseline for assessing the impact of such major changes on the bioavailability of trace metals in this estuary. This information will also be invaluable for predicting the changes likely to occur in other estuaries that become subjected to major structural changes.

The toxicity of produced formation water (PFW) originating from four natural gas production platforms located in the Adriatic Sea (Italy), and of seawater samples collected near these installations is assessed by means of bioassays with Brachionus plicatilis, with the brine shrimp Artemia franciscana and with Paracentrotus lividus. The toxicological response of these specimens was evaluated in order to identify the most sensitive one, in the consumer compartment, and to design a bioassay battery specific for samples collected in the surroundings of a gas platform. Larval mortality of rotifers, larval immobilization of crustaceans, fertilization success/failure (sperm cell test) and larval (pluteus) development success/failure (embryo toxicity test) of sea urchins were taken as ecotoxicological endpoints. The PFW sampled on two platforms resulted toxic, while no toxicity was recorded in seawater samples collected in the vicinity of the platforms, even in coincidence with the PFW discharge operations. The species and bioassays employed have shown different responses to PFW: P. lividus turned out to be more sensitive than A. franciscana and B. plicatilis. In particular, the embryo toxicity test showed a higher toxicity than the sperm cell test.

The symbiotic association between the acoel flatworm Symsagittifera roscoffensis and the prasinophyte microalgae Tetraselmis convolutae was studied regarding its photophysiology and photobehaviour. The photoacclimation status and the photophysiological responses to high light of the algal endosymbiont were studied non-destructively on individual S. roscoffensis using pulse amplitude modulated fluorometry. Specimens collected in an intertidal sandy shore were characterized regarding the maximum quantum yield of photosystem II (PSII), Fv/Fm, and the light response of photosynthetic activity, by constructing rapid light-response curves of the relative electron transport rate of PSII, rETR. The studied population could be considered as high light-acclimated when compared with other intertidal photosynthetic organisms (e.g. macroalgae), with the light-saturation parameter Ek averaging 250 μmol m−2 s−1. Light stress experiments showed S. roscoffensis to be able to withstand the exposure to high light without displaying signs of photoinhibition, suggesting the operation of efficient physiological photoprotective processes. The photobehaviour of S. roscoffensis was studied by characterizing the distribution of the flatworms under a light gradient, using a custom-made photoaccumulation chamber. The results showed a photoaccumulation pattern evidencing a clear avoidance of extreme low or high light levels, and with maximum photoaccumulation values being found for a range of irradiances (150–400 μmol m−2 s−1) that generally coincided with the optima for photosynthetic activity. This matching between the optimum light levels for photosynthetic activity and photoaccumulation suggested that S. roscoffensis may use vertical migration as a form of behavioural photoprotection. This behavioural response may be used to rapidly and flexibly control light exposure, avoiding photodamage to the endosymbiont photosynthetic apparatus by direct exposure to sunlight.

Variation in life history characteristics is believed to play an important role in dispersal and thus shaping the population and genetic structure of marine invertebrates. The genetic structure of Ibla cumingi, a small intertidal stalked barnacle that broods lecithotrophic larvae, was evaluated using 145 random amplified polymorphic DNA markers on 100 individuals from five locations across Hong Kong waters. Shallow genetic structure was observed along open-coast shores, and there was no indication of isolation by geographical distance. A significant genetic divergence, however, was observed between samples inside and outside Tolo Harbour, a semi-enclosed, sheltered and estuarine bay located in the north-eastern quadrant of Hong Kong, indicating the presence of a genetic sub-structuring pattern. In addition, relatively lower genetic diversities were described for samples inside Tolo Harbour than those from open-coast shores. This could be associated with an increase in inbreeding events attributed to local settlement caused by larval retention. This study provides an insight into how the interaction of life history and local, enclosed, hydrographic conditions could result in a substantial genetic structuring of I. cumingi over a meso-scale geographical distance.

The study presents dry mass and body measurements of the larval stages of five common barnacle species occurring in mesozooplankton catches of Southampton Water and the central Solent area of the south coast of the UK. Quantitative samples were collected with conventional 120-μm mesh plankton nets. Species-specific regression equations relating carapace width and total length with dry mass were obtained for stage II to stage VI nauplii and cyprids of Austrominius modestus, Amphibalanus improvisus, Balanus crenatus, Semibalanus balanoides and Verruca stroemia. Width–dry mass and length–dry mass regressions obtained in the present study accounted for more than 98% of the variability for naupliar stages, and length–dry mass for 80% of the variability for cyprids. The dry mass of barnacle larvae predicted from carapace width equations determined here differed by only –6% from the measured dry masses of an independent data set, suggesting these first-reported equations of barnacle larvae are useful additions to zooplankton production studies.

The endangered patellid limpet Cymbula nigra is present in the extreme western Mediterranean, yet the species has rarely been the subject of study in this region. The aim of the present research is to describe the ecology, distribution and population structure of the species in an area of the Mediterranean coast of North Africa (Ceuta). Results indicate that the species prevails in waters that have an important Atlantic influence. Furthermore, different shell morphologies are distinguished, and in consequence, a statistical analysis is carried out based on morphometric data. Based on maximum shell length, height/length coefficients and shell morphology, a total of three significantly different morphologies are described. Furthermore, considering physical parameters such as height over seawater level and average substratum inclination, juveniles resulted to be clearly segregated from the two other groups. Additionally, no differences were found regarding the topography of the substrate used by juvenile and adult individuals, although the colonized surfaces are significantly smoother than those where Patella ferruginea is present.

Although mucus plays many different roles among marine invertebrates, relatively little is known about the link between biochemical structure and function. In the present study we focused on some physical and chemical properties of the polychaete Sabella spallanzanii's mucus such as viscosity, osmolarity, electrical conductivity, elemental composition, the protein and carbohydrate content, the total lipids and fatty acid composition, and polychlorinated biphenyls (PCBs) contamination. Moreover, an antimicrobial activity of the mucus was investigated. The water content of S. spallanzanii mucus was 96.2±0.3%. By dry weight 26±1.2% was protein, 8±0.21% was carbohydrate and only 0.1% lipid, much of the remainder of the dry weight was inorganic (about 65.2%). The estimated PCBs content was <0.005 μg g−1. The mucus of S. spallanzanii exerted a natural lysozyme-like activity and produced in vitro the growth inhibition of Vibrio anguillarum, Vibrio harveyi, Pseudomonas aeruginosa and Candida albicans. The findings from this study contribute to improve the limited knowledge available on the mucus composition in invertebrates and have implications for future investigations related to employment of S. spallanzanii mucus as a source of compounds of pharmaceutical and marine technological interest.

To evaluate the effect of antioxidant defence in coelomic fluid of sea cucumber, Apostichopus japonicus in aestivation was studied in the field from July to November 2006 in Qingdao. During the sampling period, activities of superoxide dismutase and catalase increased significantly in August and November. Activities of glutathione reductase and glutathione decreased significantly in August and increased significantly in November and activities of Se-glutathione peroxidase increased significantly in August. There were no significant differences in total glutathione peroxidase. In relation to the water temperature in the field, it is known that the oxygen consumption rate dropped and antioxidant defence was enhanced in August. The structure and function of respiratory trees of A. japonicus were completely vivified as normal in November, and it is suggested that antioxidant defence was enhanced because of the sharp change of oxygen consumption. Data indicate that both enzymatic and metabolite antioxidant defences in sea cucumber are adaptable systems that are modulated during pre-aestivating stage and arousing stage.