Spatial variation in the structure of macrobenthic assemblages on intertidal flats is known to be related to different environmental variables. Most of the studies have observed that along the estuarine gradient, salinity is the most important variable driving the patterns of the macrobenthic assemblages. However, the great majority of studies have been done on single estuarine systems in temperate regions. We investigated the relationship between the macrobenthic assemblages in intertidal habitats and the environmental variables along three tropical estuaries. From lower to upper estuarine regions we sampled benthic macrofauna, salinity and sediments. The structure of the benthic assemblages was primarily related to salinity. There was a decrease in the number of taxa from the upper to the lower estuarine regions, indicating important deviation from Remane's model of estuarine diversity. There were important similarities of taxa abundance along different estuarine salinity gradients which can be properly tested in other tropical and temperate regions. We advocate that in order to adopt general and robust management practices it is essential to identify broad patterns and general rules governing estuarine systems.

Understanding the role played by sunken vessels in Mediterranean marine ecosystems is acquiring increasing importance. The aim of this research was to study the fish communities associated with four shipwrecks, by means of underwater visual censuses performed by a remotely operated vehicle, and to test the differences in composition of fish assemblages between these shipwrecks and the adjacent soft bottoms, considered as control sites. Multivariate analysis on the total fish assemblage showed significant differences between wrecks and controls. Results also showed higher levels of species richness and abundance near all wrecks than at a short distance from them on soft bottoms, thus indicating that these sunken vessels, thanks to their higher habitat complexity, act as artificial reefs, attracting aggregations of fish species and leading to a greater diversification of the local fish assemblage. Nevertheless, shipwrecks, which are an ideal target for recreational fishermen, could contribute to the over-exploitation of some high-value fish species, such as Mycteroperca rubra, Dentex dentex and Diplodus spp., attracted by the artificial hard substrate of the vessel-reefs. The recent European directives suggest an urgent need for a better understanding of the crucial role played by these potential sources of pollutants on marine environments and ecosystems. An ecosystem approach to study and monitor these pollutant sources is, therefore, mandatory for appropriate remediation and/or mitigation of the potential negative effects on a productive and healthy ocean.

In many coastal areas substrate is the limiting resource for benthic organisms. Some sessile species can be used as secondary substrate, reducing competition and increasing coexistence. In southern Chile, annual populations of Macrocystis pyrifera recruit and grow on the shells of Crepipatella fecunda. This study describes ecological interactions between the kelp and the slipper limpet over an annual cycle. The degree of kelp overgrowth was established by collecting sporophytes and through in situ submarine photography over a 10 month period (starting when kelp recruits became visible and ending when sporophytes were no longer present). Changes in the biochemical composition of the limpet tissue were also recorded by chemical analyses, to evaluate the potential effects (positive/neutral/negative) of kelp on C. fecunda nutritional condition. The results indicate that both species coexist, although kelp overgrowth may cause a decrease in carbohydrates in C. fecunda tissues, restricted to the period when the kelp forest reaches its maximum biomass. Individually, the short duration of the maximum overgrowth period and the size reached by C. fecunda females (up to 65 mm shell length) may enable rapid limpet recovery, avoiding competitive exclusion. On a population level, the M. pyrifera annual cycle generates the needed ‘break’ for C. fecunda populations, reducing the effects of kelp overgrowth. Thus, in the view of the neutral effect of kelp overgrowth, together with the positive effect of C. fecunda on M. pyrifera recruitment described somewhere else, this ecological interaction can be categorized as commensalism.

The phytoplankton community structure and abundance in the south-eastern Black Sea was measured from February to December 2009 using and comparing high performance liquid chromatography pigment and microscopy analyses. The phytoplankton community was characterized by diatoms, dinoflagellates and coccolithophores, as revealed by both techniques. Fucoxanthin, diadinoxanthin, peridinin and 19′-hexanoyloxyfucoxanthin were the main accessory pigments showing significant correlation with diatom-C r2 = 0.56–0.71, P < 0.05), diatom-C (r2 = 0.85–0.91, P < 0.001), dinoflagellate-C (r2 = 0.39–0.88, P < 0.05) and coccolithophore-C (r2 = 0.80–0.71, P < 0.05), respectively. Microscopy counts indicated a total of 89 species, 71% of which were dinoflagellates, 23% were diatoms and 6% other species (mainly coccolithophores). Pigment-CHEMTAX analysis also indicated the presence of pico- and nanoplankton. Phytoplankton carbon (phyto-C) concentrations were highest in the upper water column, whereas chlorophyll-a (Chl-a) showed a deep maximum. Average phyto-C was higher at the coastal station (291 ± 66 µg l−1) than at the offshore station (258 ± 35 µg l−1), not statistically different (P > 0.05). The coastal station also had higher Chl-a concentrations (0.52–3.83 µg l−1) compared to the offshore station (0.63–2.55 µg l−1), not significant (P > 0.05). Our results are consistent with other studies and indicate that the southern Black Sea is shifting towards mesotrophy with the increasing prevalence of dinoflagellates compared to diatoms.

Temporal variations in the taxonomic relatedness of periphytic ciliate microfauna during colonization periods were studied in coastal waters of the Yellow Sea, northern China, from May to June 2010. Samples were collected at two depths of 1 and 3 m, using glass slides as artificial substrates. The colonization dynamics of ciliate microfauna on the slides revealed similar patterns in species composition at both depths. In the immature communities (1–7 days), the taxonomic patterns showed high variability compared to those in the mature ones (10 days and more). However, taxonomic relatedness parameters at the two depths differed during early stages of colonization (e.g. 1–3 days). Taxonomic diversity (Δ) was subject to high variability (coefficients of variation >10%) in both immature and mature communities, whereas taxonomic distinctness (Δ*), average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) showed high stability (coefficients of variation <10%) during the colonization times of 3–21 days. These findings suggest that 3–21-day exposure times are sufficient to detect the taxonomic distinctness of periphytic ciliate microfauna at water depths of 1–3 m for the purposes of ecological research and monitoring of marine ecosystems.

Clownfish and their associated sea anemones are icons of tropical and subtropical coastal ecosystems, but bleaching and collecting for the aquarium trade has reduced their population densities in several Indo-Pacific locations. We surveyed four Entacmaea quadricolor populations and their associated clownfish Amphiprion clarkii in Hong Kong. These assemblages represented a combination of exposed and sheltered, flat bottomed and sloped conditions. Different from tropical areas, where E. quadricolor is usually found in sheltered shallow waters, the four populations in Hong Kong were distributed in 4–10 m depths, being densest on a 40 × 80 m slope of volcanic rocks (34.2–76.6% substrate cover and 48.7–102.1 ind  m−2) at an exposed site. This distribution pattern could be explained by the high turbidities associated with river discharge and sedimentation rates in local waters, which discourage the establishment of E. quadricolor populations in sheltered bays; shallow habitats might not be suitable for E. quadricolor in Hong Kong due to strong wave actions generated by typhoons. Amphiprion clarkii was present at low densities (0.07–0.26 fish m−2) across the sites. Our data provide a baseline for monitoring the changes of these conspicuous members of shallow water communities in Hong Kong.

The shallow water sea anemone Phymanthus crucifer exhibits three distinct morphotypes, characterized by the presence or absence of protuberances on the marginal tentacles, as well as intermediate forms. The taxonomic status of the different morphotypes and the diagnostic value of protuberances on the tentacles have been debated for this species and the family Phymanthidae. We analysed the external and internal anatomy, cnidae and three mitochondrial molecular markers for representatives of each of the three morphotypes. In addition, we address the putative monophyly of the family Phymanthidae based on molecular data. With the exception of the protuberances, our morphological and molecular results show no differences among the three morphotypes; thus, we consider this feature to be intraspecific variability within P. crucifer. Furthermore, molecular data reveal that the family Phymanthidae is not monophyletic. In addition, we discuss several diagnostic morphological features of the family Phymanthidae.

Community structure, species composition, and changes over time after disturbances are frequently studied using common descriptors. We used rank abundance distribution plots (RADs), Rényi entropy plots, common theoretical community models, ordination analysis of similarities (ANOSIM and Clusters), and abundance spectra analyses to study the effects of a gradual natural population decline and an anthropogenic punctuated disturbance on the structure of octocoral communities in Panama, considered a hot spot area for octocoral diversity in the Tropical Eastern Pacific. Over a 17-month period, no significant change was found in community structure after a natural yearly population decline of 25.2%. After a disturbance, however, different recovery trajectories were observed in various coral communities. Possible physical and biological explanations for the observed differences include initial local species diversity and abundance, species life history patterns, colony morphology, and the geographical location of the community. Differences in community structure between study sites were best described using a combination of community descriptors, RADs, and abundance spectra. Rényi plots were useful in identifying changes in community structure, whereas the extent of the changes was best evaluated using ANOSIM and cluster analysis.

A new species, Poecilochaetus anterospinus sp. nov., is described from the east and south shores of Oahu, Hawaii. Poecilochaetus anterospinus sp. nov. is unique in the genus by the presence of noto- and neuropodial spines from chaetiger 11 to posterior segments. Neuropodial spines on anterior chaetigers are absent in all other Poecilochaetus species while notopodial spines are limited to segments preceding the pygidium. Poecilochaetus cf. koshikiensis, originally described from Japan, is newly recorded from Hawaii and apparently widely distributed in the western Pacific and South-east Asian Seas. Poecilochaetus sp. is distinguished from the other two species by the distribution of the ampullaceous cirri (7–12) and its chaetal characters.

Patagonema iubatum gen. nov. sp. nov. is described from a sandy beach at Playa Pozo, Golfo Nuevo, Argentina. It resembles Oncholaimidae (Nematoda: Enoplida) and it is characterized by a buccal cavity comprising a combination of three teeth and three mandibular ridges with small teeth. The new genus is also characterized by the presence of papillose pre-cloacal supplements, cephalated spicula and a gubernaculum with dorsal apophysis and lateral piece, and a new demanian system configuration. Patagonema iubatum sp. nov. has 9–11 papillae-like pre-cloacal supplements, short and cephalated spicula and a gubernaculum with dorsal apophysis and pointed lateral piece. Its position inside Oncholaimidae is discussed.

The Mediterranean Sea is currently under siege by a conspicuous alien pressure, and, within some families (e.g. the Ostreidae), the number of native species seems to be remarkably outnumbered by that of the alien ones. We wanted to test the reliability of the molecular data currently available on the small alien oysters recently invading the Mediterranean Sea. Samples from Greece and Turkey, encompassing the known species-specific morphological variation, were sequenced for the markers with the widest taxonomic coverage in the group of small oysters (i.e. the 16S rDNA and the COI). The sequences obtained have been compared with those available in GenBank, and a possible identification at the species level has been finally tested in a DNA-barcoding fashion. The present results clearly demonstrated that our samples belong to a single, morphologically highly variable species. Their 16S sequences were closely related to a sequence registered under the name Dendostrea folium, with a genetic distance which does not warrant conspecificity. Additionally, a remarkable number of sequences retrieved from the GenBank (of both genes) did not form a monophyletic group according to the published classification of the vouchers, suggesting—at least in part—an origin from specimens not properly identified. Both genes seem promising for use as DNA-barcode, although the COI will probably prove more effective. Therefore, we urge the availability of a baseline of oyster pedigreed DNA barcode sequences in the public databases, to allow the use of such genetic data to reliably monitor bio-invasions in the Mediterranean Sea.

The veined rapa whelk is one of the most important invasive species in the Black Sea ecosystem since the 1940s. Following its introduction to the Black Sea, it destroyed most of the bivalve populations, mainly the Mediterranean mussel and oysters. However, the veined rapa whelk has commercial importance for the Black Sea fisheries as an alternative product. In this study, we aimed to determine some population parameters of the veined rapa whelk based on indirect ageing through length–frequency data by using the Bhattacharya method. We collected 1704 specimens by dredging along the coasts of Samsun Province in the Central Black Sea in 2011 from June to November. The age of the population varied from 0 to 6. Von Bertalanffy growth parameters were estimated as L∞ = 112.35 mm, k = 0.310, t0 = −0.486 and W∞ = 243.94 g. Mean length and weight, length–weight relationship, mortality and exploitation rates were derived as L = 56.80 ± 0.36 mm, W = 45.67 ± 0.89 g, W = 0.0006 L2.719, Z = 0.96, M = 0.57, F = 0.39 and E = 0.40, respectively.

T-bar anchor tags and Petersen discs were used during a preliminary mark–recapture experiment in the wild on 268 Octopus vulgaris. Discs, despite causing some injuries, were characterized by a quicker healing (within 5 days) and a higher retention rate than T-bar tags (about 97% versus 22%, respectively), therefore they were considered the best technique for tagging the animals in the subsequent growth studies. From 2010 to 2013, a total of 1604 O. vulgaris (74.4% with a total weight <300 g) were tagged with discs and released in an area of the central western Sardinian Sea (western Mediterranean Sea). Ninety-one specimens were recaptured after 4–63 days of freedom, 59 of which (31 males and 28 females) showed positive growth increments after a minimum time of 8 days at liberty. In general, a high individual variability (0.96–9.09 g day−1) and higher mean daily growth rates in females (3.07–3.65 g day−1) than in males (2.08–2.98 g day−1) were recorded, but this difference was not statistically significant. Using tag–recapture data, the first exponential growth curves for both sexes of Octopus vulgaris of small–medium size from the Mediterranean Sea were obtained, and compared with those available in the literature for the species.

The increasing market demand for Glyptocidaris crenularis shapes its great potential for aquaculture. Temperature is an important factor affecting gonad production and quality of sea urchins. Therefore, it is essential and valuable to carry out an evaluation of the temperature effects on gonad production and quality in G. crenularis before potential aquaculture. Here, we investigated the long-term effects of temperature on gonad production, colour and flavour in G. crenularis. There was no significant difference of test diameter, height and body weight between the sea urchins in high (16–23°C) and low (12–16°C) temperatures (P > 0.05). Glyptocidaris crenularis showed significantly higher gonad production and index in high temperature and in low temperature (P < 0.05). L*, a*, b* readings were slightly higher in the low temperature groups, although no significant difference was found (P > 0.05). Subjective colour and flavour ratings found that G. crenularis in the low temperature group showed significantly better colour (P = 0.003) and flavour (P < 0.001) than those in the high temperature group. The present study provides valuable and insightful information into the establishing G. crenularis aquaculture.

The sea urchin Diadema africanum is considered a key herbivore in sublittoral ecosystems of the Canary Islands. Spatial and temporal variability in population structure was carried out at Gran Canaria. We performed a morphometric and population density analysis during 2005, 2006 and 2007 at four sites in zones of Gran Canaria. The study considered a vertical gradient (5, 10 and 20 m depth) during both seasons, the cold season (February and March) and the warm season (October and November). The sea urchin D. africanum in Gran Canaria exhibited an overall density of 7.59 ± 2.92 urchin m−2. A two-way ANOVA evidenced spatial differences in mean abundance of the species, while seasonality was not relevant. The vertical analysis of the abundance of D. africanum showed differences, the smaller sizes appeared at greater depths. The Aristotle's lantern width decreased in a vertical gradient, being remarkable between 10 and 20 m. Findings of uniformity in size over time, a stable range of high densities and the lack of a relationship between the size of the sea urchins and the season reveals that the density–size strategy displayed by D. africanum which explains in turns the high stability of the urchin barrens, which, once developed, remain as areas of permanent desertification in subtidal depths throughout the Canary Archipelago.

Manta ray (Manta birostris) is the largest ray species, but little information is available regarding its biology, distribution and migratory pattern. During an aerial survey conducted in French Guiana waters (South America) in 2006, the observation of several dozen individuals all swimming in the same direction prompted us to develop a research programme on this species as part of an environmental impact assessment for oil drilling. Overall, 117 aerial surveys were performed over 3 years in order to complete a database for this species. In 54 of these flights, a total of 138 individuals were observed. A phenological analysis of this species in French Guiana waters shows a peak presence between July and December, which correlates with sea surface temperature and net primary production in the ocean. The primary production in French Guiana waters is particularly active during this period and could explain the annual pattern for this filter-feeding animal.

We examined the distribution, hatch-date, growth, and mortality of larval Benthosema pterotum, a dominant pseudoceanic myctophid in the shelf region of the East China Sea, during early autumn when the main spawning has been predicted. This species is a key species in the food web of this area. Larvae were abundant in the area south of Cheju Island (60–80 m depth), corresponding with the adult habitat. Occurrence of the larvae was restricted to the onshore side of the shelf-break salinity front, indicating that this front acted as a barrier restricting the offshore dispersion of the larvae. In the area where the larvae occurred, a cyclonic eddy is formed, which is considered to limit the dispersal of the larvae, enabling them to recruit into the area of adult habitat. Modes of hatch-date appeared from late August to early September and from mid to late September, suggesting that large-scale spawning events occurred at least twice during the spawning season. Since the modes coincided with the new moon period, B. pterotum is suggested to spawn periodically once a month around the new moon, resulting in efficient mating and fertilization. Mean absolute growth rate (0.26 mm d−1) and weight-specific growth rate (18.8% of dry body weight d−1) were higher than previously reported values of other subtropical–tropical myctophids, which would be related to the high food availability in the study area. Daily instantaneous mortality coefficient during the first two weeks after hatching was estimated to be 0.28 d−1 (equivalent to 24.7% mortality d−1).

The feeding biology of bahia sprat (Rhinosardinia bahiensis) was studied in two habitats of a tropical semi-arid estuary, on the north-eastern Brazilian coast. Samplings were collected on a monthly basis (January 2010–February 2011), and fish were caught during the day using an 8 m beach seine. Habitat use was size-dependent, with tidal mudflat occupied by higher size-classes than tidal creeks, which were occupied by smaller conspecifics. The diet analysis of different size-classes revealed that all sizes of fish consumed similar taxa (Calanoida, Cyclopoida and Decapoda larvae), and that the relative proportion of taxa consumed reflected fish size. Dietary differences between the two nursery areas mainly reflected prey availability. Although high diet overlap was only found between some size-classes in tidal mudflat, these results seem to demonstrate a strategy for efficient use of space potential; intraspecific competition was probably minimized by a differential habitat use patterns.

Otolith microstructure analysis was used to determine daily age, growth rate and hatching periods of young of the year (YOY) common two-banded seabream, Diplodus vulgaris, collected at two sites by using beach seine from Çanakkale shallow waters between January and December 2007. Total length of the YOY D. vulgaris was between 12 and 86 mm and the daily ages ranged between 42 and 313 days. Somatic growth rate estimated by fitting a linear regression to the age–length data set was calculated as 0.273 mm day−1. According to the length–age regression analysis, maximum daily growth rates were found 0.277 mm day−1 in the lowest sea temperature period and minimum values of 0.274 mm day−1 were observed in the declining sea temperature period. Analysis of covariance indicated that there were no significant differences in the linear growth equations for the two cohorts (F = 0.4008, P = 0.527). Hatching period of the YOY was estimated to occur between October and March with relatively higher frequency in January. This study has shown that YOY D. vulgaris is a winter spawner in the Çanakkale shallow waters.