Free-living nematodes were investigated in the Mar Piccolo of Taranto (Ionian Sea), a semi-enclosed basin of strategic importance for its complex productive infrastructure but in need of remediation due to the alarming amounts of heavy metals and synthetic organic contaminants in the sediments. Abundance, genera composition, biodiversity and trophic traits of nematodes were related to the gradual transition from marine to more brackish conditions and to the varying levels of contaminants in different sub-areas of the basin. Nematodes were more abundant and diverse at the most marine site while low numbers and diversity characterized the most contaminated station. Going towards the innermost part of the basin, gradually increasing values of abundance and biodiversity were observed although the assemblage was susceptible to the organic enrichment caused by mussel farms. The use of nematodes as ecological indicators mirrored the response of the assemblage to the main patterns acting in the basin (High/Good scores at the most marine site and Poor/Bad scores at the most contaminated station), giving a clear indication of environmental quality to stakeholders/authority that can contribute to address remediation actions in contaminated sediments.

Megabenthic soft bottom communities of trawlable grounds have been studied since the first few decades of the last century, thanks to trawl fishing technologies. Despite providing an extensive amount of presence data, trawling cannot be considered reliable from a quantitative point of view, frequently giving only weak information about sessile species density, large and small-scale distribution and main habitat features. The recent development of visual technologies on remotely operated vehicles (ROVs) can give a more accurate approach for the study of mega-epibenthic communities. The present study reports the application of both ROV imaging and trawling approaches for the study of a large aggregation (i.e. field) of the red sea pen Pennatula rubra in the Ionian Sea. Density, biomass and population structure were studied in the same population of P. rubra. The density assessed by ROV was significantly higher than that estimated with a three-year series of trawling surveys. Trawling gear efficiency in the removal of P. rubra was low overall. Incidental mortality can be very high due to damage to those specimens that encounter the trawl net but are not directly captured. However, sampling of several colonies by trawling was necessary to establish biometric correlations to estimates of size and biomass from ROV imaging. Trawling catch abundance/biomass data could be useful to identify areas of higher concentration of sea pens, while ROV imaging can be used to monitor these fields in a non-destructive manner that would be consistent with protection measures.

Investigation of parasites and diseases affecting molluscs of ecological and economic interest is critical for the management of native stocks and aquaculture. In recent years, much attention has been devoted to investigating the World Organisation for Animal Health listed infectious diseases, so that communities can be prepared to attend public health emergencies and avoid severe income losses. In this context, the health status of Mytilus galloprovincialis Lamarck, 1819 was analysed in two aquaculture sites (Strunjan Bay and Piran Bay, Slovenia), and in four natural mussel beds (Adriatic Croatia International Marinas Pula and Rovinj and St Catherine, Croatia; Marina Koper, Slovenia) along the coast of the northern Adriatic Sea. The mussels were sampled in February and April 2014, and processed for histological examination of several endosymbionts and pathogens that frequently occur in mytilid mussels. Endosymbionts and pathogens were not detected in farmed mussels. Prokaryotic inclusion bodies, the protozoan Nematopsis, Ancistrocoma-like ciliates, haplosporidian-like plasmodia, turbellarian Urastoma cyprinae, and basophilic inclusion bodies were observed in digestive gland cryosections of wild mussels from the coastal region of the northern Adriatic. Fungal spores of Psilocybe sp., Ulocladium sp. and Alternaria sp. were detected between the digestive tubules based on their morphology. Diagnostic PCR did not reveal infection with Marteilia refringens during the studied period, neither in wild nor farmed mussels. We confirmed the site effects on prevalence of infected mussels. Thus, we can conclude that wild areas are more exposed to endobionts and parasites than aquaculture sites.

To study zooplankton–phytoplankton relationships in the diatom-dominated plankton communities of the northern Adriatic we performed feeding experiments with diatoms and zoea I larvae of the brachyuran Xantho poressa. We found that zoea I of X. poressa feed on diatoms of different forms (centric, pennate, colony forming, single celled, with or without setae) and size classes. In a laboratory setup, we presented the zoeas with a mix of diatom species similar to communities observed during blooms regularly found in the northern Adriatic. We report that the grazing activity resulted in a decrease of the relative abundance of the toxic diatom Pseudo-nitzschia calliantha. For the colonial, bloom-forming diatom Skeletonema marinoi our results show a chain length reduction in the presence of zoea I. Of particular interest is the observation that the presence of larvae also resulted in an increased growth rate and abundance of S. marinoi, which resembles bloom induction by grazer presence.

The study of copepod assemblages indicated the presence of 22 species and 12 families in the southern coast of Sfax, 20 species and 13 families in the northern coast and 14 species and 8 families in the Ghannouch area, with a dominance of Oithonidae (79, 51 and 43% in the southern, northern and Ghannouch coasts, respectively). The relative abundance and the richness diversity of Oithonidae were found to be the most relevant indicators of anthropogenic pollution. Oithona nana, Euterpina acutifrons and Acartia clausi differed significantly in abundance between these three areas under differing degrees of pollution. The study of the structure, composition and density of the copepod fauna showed that the southern coast was a pollution-resistant ecosystem (H′ = 1.49 ± 0.33 bits ind−1; 22 species; density = 51.375 ± 4.340 × 103 ind m−3) followed by Ghannouch area (H′ = 1.74 ± 0.28 bits ind−1; 15 species; density = 11.979 ± 5.651 × 103 ind m−3) and the northern coast, considered as a restored area (H′ = 1.95 ± 0.26 bits ind−1; 21 species; density = 6.516 ± 4.304 × 103 ind m−3). The three ecosystems can thus be classified according to their degree of resistance to the anthropogenic inputs based on the results of the physico-chemical parameters and the species diversity as follows: southern coast > Ghannouch area > northern coast.

The presence of potentially toxic elements (PTE) was determined in different tissues of five selected marine organisms. The As, Cd, Cu, Mn, Mo, Ni, Pb and Zn concentrations were measured in the seagrass Cymodocea nodosa, the green alga Cladophora echinus, the red alga Gelidiella lubrica, the marine topshell Phorcus turbinatus and the littoral crab Carcinus aestuarii, as well as in seawater from Makirina Bay. The levels of As, Cd, Cu, Mn and Zn in the biota were found to exceed those in previously analysed sediments, indicating the bioaccumulation of these PTE. The biota-sediment accumulation factor (BSAF) and concentration factor (CF) varied among different organisms. As regards the five selected species, C. nodosa, C. echinus and G. lubrica proved to be the strongest accumulators of Mn, while P. turbinatus and C. aestuarii showed a high capacity to accumulate As, Cd, Cu and Zn. These species can be considered as good ecological indicators in the assessment of PTE pollution in marine littoral environments.

This study presents patterns of spatial and temporal variation in the meiofaunal community and nematode associations on the volcanic sandy beaches of Trindade Island, a remote oceanic island in the South-east Atlantic Ocean. Samples were collected in August (rainy season) and December 2014 (dry season) on four beaches (Tartarugas, Parcel, Cabritos and Portugueses) at three zones of the intertidal (high, mid and low). A total of 10 meiofaunal groups were found. Copepods (31%) and nematodes (27%) dominated the meiofauna in all beaches and zones, regardless of the season. Nematodes were comprised mainly of non-selective deposit feeders, with a total of 27 genera from 12 families, with Cyatholaimidae, Xyalidae and Oncholaimidae as the most diverse and abundant. Significant differences were found in the meiofaunal community, as well as in nematode associations, among seasons and intertidal zones but not among beaches. The sediment characteristics were the main drivers regulating the structure of meiobenthic fauna in Trindade Island. Our findings are also compared to other studies focusing on the meiofauna and nematodes of oceanic islands with carbonate and volcanic sediments; the major patterns are herein presented.

Invasive algae can have substantial negative impacts in their invaded ranges. One widely cited mechanism that attempts to explain how invasive plants and algae are often able to spread quickly, and even become dominant in their invaded ranges, is the Enemy Release Hypothesis. This study assessed the feeding behaviours of two species of gastropod herbivore from populations exposed to the invasive alga Sargassum muticum for different lengths of time. Feeding trials, consisting of both choice and no-choice, showed that the herbivores from older stands (35–40 years established) of S. muticum were more likely to feed upon it than those taken from younger (10–19 years established) stands. These findings provide evidence in support of the ERH, by showing that herbivores consumed less S. muticum if they were not experienced with it. These findings are in accordance with the results of other feeding-trials with S. muticum, but in contrast to research that utilizes observations of herbivore abundance and diversity to assess top-down pressure. The former tend to validate the ERH, and the latter typically reject it. The potential causes of this disparity are discussed, as are the importance of palatability, herbivore species and time-since-invasion when considering research into the ERH. This study takes an important, yet neglected, approach to the study of invasive ecology.

This study intends to reliably estimate the general status of the benthic and the epiphytic foraminifera community related to each studied seagrass ecosystem (Posidonia oceanica, Cymodocea nodosa and Halophila stipulacea) distributed in different shallow sites in the coastal archipelago of Kerkennah (Gulf of Gabes, Tunisia) during winter. We were able to first sort and subsequently identify some characteristics conditioning their behaviour. Twenty-four species of foraminifera were encountered. Among them, three epiphytic species identified on these seagrass leaves had a much lower abundance than those in the sediment. We were interested in highlighting the foraminiferal community related to Halophila stipulacea, since this seagrass species is newly introduced into the Mediterranean sea. Thanks to the statistical study, we were able to identify the favourable habitat for epiphytic and benthic foraminifera among the three seagrass ecosystems. A correlation between the identified foraminifera species and some environmental parameters was addressed using a variety of software.

The invasive sabellid Branchiomma bairdi (McIntosh, 1885) was collected in the Estany des Peix lagoon (Formentera Island, Balearic Sea, Western Mediterranean). This species is native to Bermuda (Western Atlantic Ocean), being widely distributed through the Caribbean Sea. However, it has been described as invasive worldwide, being also present in the Indo-Pacific region, the Eastern Atlantic Ocean and the Mediterranean Sea. We here provide the first record of the species for the Balearic Sea, together with a comparison to other morphologically similar alien species, Branchiomma boholense (Grube, 1878), which is supposed to have also been introduced in the Mediterranean basin. We also include comprehensive taxonomic descriptions of both taxa based on the type material, a dichotomous key for the Mediterranean species of Branchiomma and hypothesize the most likely way of introduction of B. bairdi in the Balearic region.

Polychaetes of 31 species from 17 families (Amphinomidae, Chrysopetalidae, Eunicidae, Glyceridae, Hesionidae, Iphionidae, Lumbrineridae, Maldanidae, Nereididae, Oenonidae, Phyllodocidae, Polynoidae, Sabellidae, Serpulidae, Syllidae, Terebellidae, Trichobranchidae) were studied from five locations around Abu Musa Island, the Persian Gulf. Perinereis iranica sp. nov. is described as a new species for the Persian Gulf. Perinereis iranica sp. nov. is most similar to members of the Perinereis cultrifera species complex, which are also found in the Persian Gulf, but can be most easily distinguished from them by the number, shape and arrangement of paragnaths in Areas V and VI. Perinereis camiguana is compared to members of the genus Pseudonereis, and found to resemble them closely, but until type specimens can be re-examined, we recommend treating this species as Nereidinae incertae sedis. Fifteen species, belonging to 13 genera: Eunice ‘sp_Abu Musa’, Marphysa ‘sp_Abu Musa’, Glycera cf. tesselata, Hesione splendida, Lumbrineris ‘sp_Abu Musa’, Notoproctus ‘sp_Abu Musa’, Nereis sp. cf. N. pelagica, Eteone ‘sp_Abu Musa’, Harmothoe liaoi, Potamilla ‘sp_Abu Musa’, Branchiosyllis cf. exilis, Trypanosyllis ‘sp. 1_Abu Musa’, Trypanosyllis ‘sp. 2_Abu Musa’, Terebella ‘sp_Abu Musa’, Terebellides cf. stroemi are reported for the first time from the Persian Gulf; nine species remain to be named formally. Three genera: Notoproctus, Eteone, Terebella are recorded for the first time from the Persian Gulf.

Pleuroncodes monodon, an important fishery resource and key species in the Humboldt Current Large Marine ecosystem, has a prolonged reproductive period from winter until end of summer, and during this time females incubating their embryos are exposed to seasonal variation in food availability and in temperature. Additionally, in order to ensure successful reproduction and survival of embryos, changes occur in the main internal reserves and/or sources of energy of P. monodon. The aim of this study was to determine the extent of seasonal variation (winter vs summer) in the lipid content and fatty acid composition of ovigerous females and their embryos. The results show that a higher percentage of saturated and polyunsaturated fatty acids are found in females in winter. Similarly, the composition of fatty acids in embryos found here indicates that winter embryos have more saturated fatty acids and essential fatty acids (C18:2n6cis, C18:3n6 and C22:6n3) than do summer embryos. According to PCA analysis of fatty acid profile, samples from summer may be distinguished into two isolated groups with conspicuous variations in fatty acids profile of embryo and hepatopancreas. While in winter, the opposite pattern occurs in the fatty acid profile of embryo and hepatopancreas. These variations may be related to relevant physiological processes (reproduction and growth) and of their ontogeny (development and survival of offspring). Seasonal variation in the lipid content and composition of fatty acids of P. monodon could directly impact this species’ reproduction and survival and subsequently could have consequences on the food web and fishery exploitation.

New Zealand rattail fish are of great interest both to biologists who study their phylogenetics and in fisheries. In contrast, their morphological evolution is little studied and poorly understood. Geometric morphometric methods based on scale shape were applied in this study to determine differences among species and genera. Scale shapes were described using seven landmarks, the coordinates of which were subjected to a generalized Procrustes analysis, followed by a principal components analysis. A cross-validated discriminant analysis was applied to assess and compare the size-shape (centroid size plus shape variables) efficacy in the species and the discrimination of the genera. Two main phenetic groups were identified: cluster no. 1 with eight species and cluster no. 2 with six species. Coelorhinchus aspercephalus and Mesovagus antipodum were more separated from the other species in the first cluster. The cross-validated canonical discriminant analysis correctly classified 74% at the genus level, with most misclassifications occurring between Coelorhinchus and Coryphaenoides, whereas the best classified genera were Mesovagus and Trachyrincus. The discrimination of correctly classified species ranged from 41.2 to 100%. The highest correct classification rates were recorded for Coryphaenoides armatus, Coelorhinchus innotabilis, Trachyrincus longirostris and Mesovagus antipodum.

Mytilaster minimus is widely distributed along the rocky intertidal of much of the Mediterranean's coastline and the Adriatic Sea. Populations are, however, threatened by the Lessepsian invader Brachidontes pharaonis that occupies the same habitat and is more tolerant of environmental extremes. This is the first study of the anatomy of M. minimus in relation to its evolution and adaptations towards an intertidal life on the karsted limestone shores that characterize much of the Mediterranean. In most anatomical respects M. minimus is a typical mytilid but is small (<16 mm shell length) and, post-juvenile, greatly deformed concomitant with its niche of colonizing pits in the karsted rocks. It is thus generally squatter, that is, dorso-ventrally flattened, laterally expanded and antero-posteriorly foreshortened in comparison with M. galloprovincialis. A pair of statocysts has been identified in the visceral mass. Most interest, however, resides in the fact the posterior byssal retractor muscles, like the shell, are foreshortened to comprise one paired block and the posterior pedal retractor muscles are situated beneath these not anterior to them as in other mytilids. These adaptations equip M. minimus for a compressed, squat, life in the intertidal karst. In addition to competition from the introduced B. pharaonis in the Mediterranean, M. minimus is facing competitive exclusion from the native Mytilus galloprovincialis that, as a result of intensive and increasing mariculture, is coming to dominate Croatian shorelines. This study is, therefore, prescient in laying the foundations for future research on what is becoming a threatened native Mediterranean species.

The slipper limpet Crepidula fornicata ranks among the main invasive species on French coasts and is known to cause ecological impacts on food web structure and nutrient cycling. This study investigated the effect of C. fornicata on different components of benthic megafauna diversity (species composition, α-, β- and γ-diversity). In Arcachon Bay (France), C. fornicata was present in 58% of the 221 sampling stations. Crepidula fornicata was particularly abundant in four of the main benthic megafauna assemblages, suggesting a non-random distribution of its population. The mean number of megafauna species per station (α-diversity) was 11 with C. fornicata vs six without. Conversely, community similarity among stations (β-diversity) was higher when C. fornicata biomass increased. Opposing α- and β-diversity trends in the presence of C. fornicata explained the similarity of the global number of species (γ-diversity) between both situations (with and without C. fornicata). These results highlighted how this exotic engineer species acted on different types of diversity: the presence of C. fornicata increased the number of species per sample (α-diversity) but homogenized the benthic community (decreasing β-diversity) in comparison with stations where C. fornicata was absent. Crepidula fornicata stock in Arcachon Bay was also monitored and compared with 1999. The spread of C. fornicata between 1999 and 2011 has been limited with a 318 t stock which was not statistically different than the previous estimate performed in 1999. However, the mean length of C. fornicata collected in 2011 was significantly smaller, mainly due to a higher proportion of small individuals.

Coastal ecosystems are particularly vulnerable to alien invasions. Regular, standardized, targeted monitoring of coastal areas helps to detect the arrival of non-native species early, identify sites most vulnerable to invasion, and assess potential for further spread. This study quantified the spread and changes in distribution of non-native oyster, Crassostrea gigas, populations around the coast of Ireland. In total 37 sites were surveyed, in areas which either currently or previously harboured cultivated C. gigas, for the presence and abundance of ‘wild’ C. gigas. Wild populations were identified at 20 sites and at four additional sites C. gigas was observed as recently discarded from aquaculture activity. Five of the invaded sites were identified as being highly suitable for a population expansion based on their current population status. Importantly, we also identified individuals of C. gigas and native European oysters, Ostrea edulis, co-occurring within the same shore at five sites. This is the first record to our knowledge of such co-occurrence within Europe. This evidence of co-existing oyster species raises concerns regarding the potential impact of C. gigas on recovering O. edulis populations. In Ireland, however, C. gigas does not typically spread extensively from introduction points, and although self-containing populations exist, they are currently sustained at a much lower density than those observed in other regions such as the Wadden Sea or French Atlantic coasts. We suggest, therefore, that to protect native oyster populations, C. gigas should be eradicated where co-occurring with O. edulis and recommend continuous monitoring of invaded sites.

The sea cucumber Apostichopus japonicus is a deposit-feeder and vital for marine benthic ecosystems. Hypoxia can influence the behaviour and even lead to massive mortality in A. japonicus in the wild. It is important to understand the molecular responses of A. japonicus when exposed to acute changes in dissolved oxygen (DO) concentration. In this study, RNA-seq provided a general overview of the gene expression profiles of the respiratory tree of A. japonicus exposed to DO of 8 mg l−1 (DO8), 4 mg l−1 (DO4) and 2 mg l−1 (DO2) conditions. Differentially expressed genes (DEGs) screening with the NOISeq method identified 51, 59 and 61 DEGs according to the criteria of fold change ≥2 and divergence probability ≥0.8 in the comparisons of DO2 vs DO4, DO2 vs DO8 and DO4 vs DO8, respectively. Gene ontology analysis showed that ‘cellular process’ and ‘binding’ had the most enriched DEGs in the categories of ‘biological process’ and ‘molecular function’, respectively (catalytic activity also had the most enriched DEGs in the category of ‘molecular function’ based on the comparison of DO2 vs DO8), while ‘cell’ and ‘cell part’ had the most enriched DEGs in the category of ‘cellular component’. The DEGs were mapped to 79, 81 and 104 pathways in the KEGG database, and 8, 29 and 16 pathways were significantly enriched, respectively. The DO-specific DEGs identified in this study of the respiratory tree are important targets for further research into the biochemical mechanisms involved in the response of the sea cucumber to changes in the DO concentration.

The aim of the present work is to report and describe three new species of the tropical brittle-star genus Ophiolepis. The new species are described herein as Ophiolepis aemulata sp. nov., Ophiolepis buitronae sp. nov. and Ophiolepis crebra sp. nov. As these species were previously misidentified, morphological traits and similarities between them and other species are extensively discussed. Ophiolepis buitronae sp. nov. is widespread in tropical and warm waters of the western Atlantic from intertidal to 36 m. It has consistently been misidentified as Ophiolepis impressa as these two species share a similar distribution and are found together. Ophiolepis aemulata sp. nov. is found in western Australia, as are its congeners Ophiolepis superba and Ophiolepis unicolor, while Ophiolepis crebra sp. nov. is found in Australia and Indonesia. There are 25 extant species, including the three new species, which are currently referred to the genus Ophiolepis.

Coral communities of the Persian Gulf (PG) withstand maximum and annual ranges of water temperatures that surpass those found on the majority of reefs elsewhere. As such, these communities may inform on how coral reefs might adapt to the warmer waters of the future. Depending on the algal symbiont (genus Symbiodinium) harboured, advantages in stress tolerance may be conferred to the coral holobiont. Characterizing the algal component is therefore critical in determining the coral holobiont's tolerance phenotype. Coral associations off the Arabian coastline of the PG have been characterized as biogeographically unique, containing a rare group of taxonomically ancestral and thermotolerant algal symbionts, the Symbiodinium thermophilum group. In contrast, waters off the Iranian coast remain poorly characterized with a notable lack of S. thermophilum group symbionts identified in coral associations to date. Here, we characterize the algal component of two reef building corals (Porites harrisoni and Cyphastrea microphthalma) predominant at three sites spanning almost the entire length of the PG's Iranian coast. Genotyping using the chloroplastic 23S and nuclear ITS2 genes, we demonstrate the presence of S. thermophilum group symbionts. We discuss the probable physical drivers of these associations and highlight the need for further research in these relatively understudied waters.