In September 2014 a group of 130 marine biologists from 26 countries assembled in the 49th European Marine Biology Symposium (EMBS) held in Saint Petersburg, Russia. The EMBS is a series of annual conferences providing presentations and dialogue in a fairly informal atmosphere – the perfect conditions for encouraging interactions on state-of-art issues in marine science in Europe and beyond. The 49th symposium, organized by the Zoological Institute of the Russian Academy of Sciences, included four keynote lectures, 65 oral presentations and 92 poster contributions under the overarching theme ‘A variety of interactions in the marine environment’.

The degree of development and operability of the indicators for the Marine Strategy Framework Directive (MSFD) using Descriptor 1 (D1) Biological Diversity was assessed. To this end, an overview of the relevance and degree of operability of the underlying parameters across 20 European countries was compiled by analysing national directives, legislation, regulations, and publicly available reports. Marked differences were found between countries in the degree of ecological relevance as well as in the degree of implementation and operability of the parameters chosen to indicate biological diversity. The best scoring EU countries were France, Germany, Greece and Spain, while the worst scoring countries were Italy and Slovenia. No country achieved maximum scores for the implementation of MSFD D1. The non-EU countries Norway and Turkey score as highly as the top-scoring EU countries. On the positive side, the chosen parameters for D1 indicators were generally identified as being an ecologically relevant reflection of Biological Diversity. On the negative side however, less than half of the chosen parameters are currently operational. It appears that at a pan-European level, no consistent and harmonized approach currently exists for the description and assessment of marine biological diversity. The implementation of the MSFD Descriptor 1 for Europe as a whole can therefore at best be marked as moderately successful.

The hydroid and hydromedusa fauna of Russian Arctic seas, totalling 161 species, has been revised taxonomically and biogeographically. Diversity is highest in the Barents Sea, where 133 species are known to occur. Species composition of Hydrozoa throughout Russian Eurasia is decidedly uniform, with marked similarity among all regional faunistic lists. An assemblage of Arctic ubiquitists, a majority of them boreal-Arctic species, comprise the main element of hydrozoans in all Arctic seas. This faunistic main element is responsible for the faunal uniformity observed from one sea to the next across thousands of kilometres along the northern Eurasian coast. Exceptions occur in marginal regions including western parts of the Barents Sea and south-eastern parts of the Chukchi Sea, where species distribution area contours (named as ‘synperates’) come close together. Based on a biogeographic analysis of faunistic data and species distributions of Hydrozoa, all temperate and cold waters of the Eurasian seas and the Central Polar Basin were referred to a single Arctatlantic biogeographic realm. Biogeographic subdivisions within this realm have rather low hierarchical rank, the result of low endemism, high faunal similarity across the northern seas, and predominance of a North Atlantic fauna in Russian northern seas as far as the easternmost Chukchi Sea.

The first offshore liquefied natural gas (LNG) terminal in Italy and the first gravity based structure (GBS) in the world for unloading, storing and re-gasifying liquefied natural gas, was authorized and realized. The Institute for Environmental Protection and Research (ISPRA, formerly ICRAM) formulated and implemented a multidisciplinary monitoring plan at verifying possible impacts of the project on marine environment. Data from June 2006 to July 2012 on the soft-bottom macrozoobenthic assemblages around the LNG terminal are presented, with the aim of verifying possible disturbances on these assemblages associated with the LNG terminal, by comparing the structure of the benthic communities before and after installation of the terminal, and during its operation. Well-structured assemblages were observed for the entire period investigated, with all taxa normally represented both quantitatively and qualitatively. A temporary disturbance due to the construction of the LNG terminal was detected in the surrounding sediments, while the presence of the concrete structure did not show significant effects at the investigated distances.

For the first time the meiofauna of the rocky walls of a submarine cave was studied. The cave, known as il Ciolo (Strait of Otranto, south-east Italy) is a closed tunnel about 125 m long, with a maximum depth of 6 m below sea level. The meiofauna was collected from artificial panels and natural rocky walls. This double approach enabled: (1) the description of the community's initial organization (on artificial substrata), and (2), especially for Harpacticoida, its mature composition (on rocky walls), which also helped to establish spatial differences. The collected samples yielded 70 taxa in total. Harpacticoida represented the most important group of organisms in terms of both abundance and identified taxa. The meiofauna assemblage appeared not to be affected by community age, with the exception of the very early stage. The meiofauna of the cave showed assemblage differences from the entrance to the innermost positions, but not as evident as in the case of the macrobenthos. The similarity of community composition at different ages (6, 12 and 24 months) and at different positions along the cave could be the consequence of the specimens’ vagility.

The structure of the microbial food web was studied in six estuary areas along the eastern Adriatic coast during March, July and October 2012. Limitation by phosphorus, not nitrogen, was a common feature for all studied estuaries. Heterotrophic bacteria and autotrophic picoplankton (APP) (particularly picoeukaryotes and Synechococcus) can reach notable abundances and biomasses, suggesting potential importance of the picoplankton community in P-limited estuarine environments. The main features of the microbial community structure in these environments included: (1) higher heterotrophic biomass in comparison to autotrophic biomass within the picoplankton community; (2) general domination of picoeukaryotes within the APP community, and increase of absolute and relative biomass of prokaryotic autotrophs (Prochlorococcus and Synechococcus) in the total APP in P-limited conditions; (3) domination of Synechococcus over Prochlorococcus biomass in all studied conditions, and common spatial distribution of these two groups of cyanobacteria, which was mostly determined by concentration of phosphorus; (4) relatively high contribution (about 50%) of LNA bacteria in the total bacterial abundance; and (5) relatively high contribution (about 33%) of heterotrophic pico-flagellates in the total flagellate abundance.

Due to postglacial isostatic uplift many stratified lakes, at different stages of isolation, are located along the shores of the White Sea. In five lakes, located near the White Sea Biological Station of Moscow State University, salinity, temperature, pH, concentration of dissolved oxygen, redox potential, and illuminance were measured. Distribution of microorganisms and spectral properties of water layers were also studied. All the lakes had a narrow bright coloured layer in the redox zone caused by mass development of phototropic microorganisms. Light absorption and fluorescence spectra indicated algae containing chlorophyll a predominate in the red water layers while the colouration of green and brown layers is caused by green sulphur bacteria with bacteriochlorophylls d and e. Sunlight is completely absorbed in the redox zone because of the high density of algae and/or bacteria, resulting in aphotic conditions below. Coloured layers act as a specific biotope for special communities of microorganisms. Eukaryotes identified by the 18S rRNA gene included different species of mixotrophic algae and ciliates resistant to anoxia. The water layer colour and spectral characteristics (i.e. light absorption and fluorescence) of water in the redox zone can be considered indicators of the stage of lake isolation from the sea, with the red colour caused by cryptophyte alga Rhodomonas sp. bloom found in earlier stages and brown and green colours caused by green sulphur bacteria in later stages.

This is the first comprehensive research study on the parasites of Mytilus galloprovincialis collected from the Sinop coasts of the Black Sea and their relationships with several environmental and biotic factors. A total of 1740 mussels were collected monthly at three sampling localities representing different ecosystems in the period between August 2012 and July 2013 and examined for parasites. Identified parasites were Nematopsis legeri, Peniculistoma mytili, Urastoma cyprinae, Parvatrema duboisi and Polydora ciliata. Infection prevalence (%), mean intensity and mean abundance values of each parasite species were calculated according to season, sampling localities and length classes of mussel. Nematopsis legeri was the most prevalent species (32.5%), followed by Pe. mytili (6.70%), U. cyprinae (6.30%), Pa. duboisi (4.50%) and Po. ciliata (2.20%). Nematopsis legeri and Parvatrema duboisi had their highest infection prevalence and intensity values in sampling locality III where secondary hosts present to complete their life cycle and larger sized mussels had higher parasite loads. Statistically significant differences were determined in the prevalence of infection and intensity values among seasons, length classes of mussel and sampling localities of each parasite species. The present study provided valuable information on mussel parasites and their relationships with host length, seasons and ecology.

Many size-selective predators switch their diet during ontogeny. At the White Sea, the adult moonsnails Amauropsis islandica feed mostly on Macoma balthica clams. The diet of juveniles was largely unknown. We conducted a field survey and a caging experiment to find out if juvenile moonsnails can prey on Hydrobia ulvae, and whether they prefer this snail to their usual prey. Live molluscs and their intact or perforated shells were collected from 34 sediment cores. We exposed the single-prey cages with 50 Macoma (MP) or 50 Hydrobia (HP) together with five Amauropsis juveniles, as well as the cages where both prey species were in a 25:25 proportion (HMP). While live Hydrobia was more abundant in the natural assemblages, Amauropsis preferred Macoma, as indicated by proportions of perforated shells. The caging experiment produced similar results. Per capita Macoma consumption rate was significantly higher than Hydrobia consumption rate (6.4 ± 0.5 mg day−1 ind.−1vs. 1.4±0.2 mg day−1 ind.−1 in MP and HP respectively). Prey consumption rates in the single-prey treatments were higher than in mixed-prey cages regardless of prey species. Different mechanisms explain this variation: for Hydrobia it is a consequence of the dietary shift, while for Macoma it reflects the ‘floor’ effect in HMP cages, where virtually all Macoma had been drilled by the end of exposure term. While Macoma is the preferable prey of young Amauropsis, Hydrobia can supplement the diet of juveniles when Macoma is scarce in certain locations.

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

Density distribution of the common infaunal bivalves, Macoma balthica and Cerastoderma edule, was studied along the Murman Coast of the Barents Sea during 2002–2010. In both species, abundance was generally higher in West Murman in contrast to East Murman. Highest density of Macoma balthica reaching 1535 ind. m−2 was observed in the Kola Inlet. Cerastoderma edule was less abundant; its density rarely exceeded 10 ind. m−2 in all but one site, where 282 ind. m−2 was registered. Reconstruction of abundance distribution across the European geographic range of Macoma balthica revealed that it does not match an ‘abundant-centre’ pattern, having features of ramped north. On the other hand, distribution of Cerastoderma edule abundance across the range generally follows an ‘abundant-centre’ pattern but southern edge populations show relatively higher abundances as compared with those at the north edge (the Barents Sea).

This study examines the effect of water temperature on the formation of shell sculpture in young molluscs of the genus Hiatella. The larvae of H. arctica and H. gallicana were maintained under laboratory conditions at different temperature regimes. The animals were reared from late veligers to juveniles with a shell length of 700 μm. The results of the experiment showed that the shell sculpture, which is a diagnostic species character, was developed to various degrees at different temperatures. The larvae of each species grew to juveniles with variously pronounced shell sculptures ranging from a complete absence of sculpturing to its maximum development. The individuals with smooth shells like those of H. gallicana were the most abundant among the molluscs reared at +5°С. At +12°С, all molluscs formed ridges and two rows of long spines in the posterior portion of the shell, which is typical for H. arctica. At +8°С, the molluscs developed various intermediate forms of shell sculpture. It was, therefore, demonstrated that the development and prominence of shell sculpture is determined by environmental temperature. These results are discussed with regards to the validity of using shell sculpture as a taxonomic character for species in the genus Hiatella.

Alterations of membrane lipid composition (cholesterol, phospholipids and their fatty acids) in response to various temperature changes were studied in blue mussels Mytilus edulis L. from the White Sea. Lipid composition changes after acute temperature stress, especially a temperature drop, included a significant reduction of the membrane phospholipid content directly (1 h) after return to the initial temperature, which was presumably a consequence of a non-specific stress reaction in the mussels. A longer recovery period (24 h) as well as long-term temperature acclimation (14 days) induced changes in gill fatty acid composition (for instance, a rise in phospholipid unsaturated fatty acids under low temperature impact), indicating ‘homeoviscous adaptation’ to maintain the membranes in response to temperature fluctuations. Moreover, the gill cholesterol level in mussels varied especially at long-term temperature exposure.

Today, three-spined stickleback Gasterosteus aculeatus are the most abundant fish in the White Sea and are close to their historical maximum. Based on observations from 2011–2013, this study reports quantitative and qualitative characteristics of juvenile stickleback diet during periods of active feeding in coastal Zostera seagrass beds. The following planktonic taxa dominated stomach contents: copepods Temora longicornis and Microsetella norvegica, ciliophora Helicostomella subulata. Benthic organisms such as Oligochaetae and Orthocladiinae also played an important role, whereas the literature suggests they were once rare in marine stickleback diets. Consumption patterns depended on fish size, with the most pronounced diet shift taking place as juveniles reached a length of 15 mm, in late August. In larger juveniles the highest correlation between the abundance of food organisms in stomachs and in the sea was observed for Orthocladiinae, suggesting that they are the preferred food. Overall, changes in diet followed changes in the abundance of available food organisms, but food selectivity analysis of planktonic organisms showed that M. norvegica were actively selected by juveniles.

We analysed 267 zooplankton samples collected in the South Brazilian Bight (SBB; 23–27°S) to determine whether hydroids, typically benthic, are common components of the pelagic SBB. Two species, Clytia arborescens, recorded for the first time in the Atlantic Ocean, and Clytia sp. were identified. While these planktonic hydroids were frequent or relatively so in shallow shelf waters (~23% of the samples <50 m isobaths, and 5% of the samples >100 m), abundances were low (up to 61 hydranths m−3) suggesting a low trophic impact. Such colonies are probably fragments of benthic colonies detached by storms and/or tides. Given the good condition of the coenosarc, existence of gastric content, and presence of reproductive structures, development of these species appears to be normal in the pelagic environment. Existence in the plankton may increase their capacity for dispersion.

The 230 km long coast of Alagoas State, in north-eastern Brazil, has diverse reef ecosystems, made from corals and of sandstone, that harbour a wide range of marine invertebrate fauna. Little is known about turbellarians of the order Polycladida in most parts of the Brazilian coast, with no record from Alagoas up to date. To fill this gap expeditions were conducted on the reefs from the central coast of Alagoas, where 11 Polycladida species were found: Pericelis cata, Enchiridium evelinae, Pseudoceros bicolor and a possible new colour variation of this species, Pseudoceros rawlinsonae, Pseudobiceros pardalis, Thysanozoon brocchii, Thysanozoon alagoensis sp. nov., Armatoplana leptalea, Adenoplana evelinae, Latocestus brasiliensis, Phaenocelis medvedica. The species are described in detail through photos of live specimens and histological sections. The present work adds six species to the north-eastern Brazilian coast, one of them a new species, and all 11 species are for the first time reported from Alagoas State. Also, it is the first time that Phaenocelis medvedica, Adenoplana evelinae, Latocestus brasiliensis and Armatoplana leptalea are illustrated by full colour photos of live specimens and histological sections.

Nebalia mediterranea sp. nov. (Crustacea, Leptostraca) is described from the Aegean coast of Turkey and Northern Cyprus. The new species is closely related to other sympatric species in the eastern Mediterranean, N. strausi and N. kocatasi, according to general body appearance. The new species differs, however, from other Nebalia species in having a rostrum about 2.5 times as long as wide, the antennular scale is clearly more than twice as long as wide, the fourth article of the antennule has only one short thick distal spine, the third article of the antenna has three similar spine-like setae on external lateral face, the first article of the second maxilla endopod is 1.2 times as long as the second article, the exopod of the second maxilla is longer than the first article of the endopod, pleonites 5–7 have distally rounded to slightly truncated denticles along posterior dorsal borders, the protopod of pleopod 4 has 4 serrations along posterior border, and the terminal seta of the uropods is about 1.8 the length of rami.

Recent observations of unusual mass stranding and mortality of two Indian Ocean crustacean species, the swimming crab Charybdis smithii and the mantis shrimp Natosquilla investigatoris, are documented and analysed. Strandings of C. smithii were observed for the first time in the equatorial Indian Ocean, the main area of its pelagic distribution. Strandings of mantis shrimps are reported from throughout the western Indian Ocean; occurrences of mass stranding in the Maldives Archipelago mark an extension of the known range of N. investigatoris into the central Indian Ocean. Mortality of crabs probably represents a ‘catastrophic event’. In contrast, mantis shrimp strandings, which were always associated with a sudden increase of its biomass (‘blooms’), are apparently post-reproduction mortalities indicating potential semelparity for this species.

The current study investigated basic biological features for two co-occurring shore crabs Pachygrapsus marmoratus and P. transversus in the eastern Mediterranean Sea. Differences in population structure, reproductive periods and settlement patterns were studied along the coast of Lebanon. Sizes of sampled individuals ranged from 4 to 37 mm carapace width (CW) for P. marmoratus and from 3.5 to 24 mm CW for P. transversus. Males were larger than females in both species, each of them exhibiting different size frequency distributions. Both male and female proportions were similar for P. marmoratus while males dominated the population of P. transversus. Fecundity and egg sizes were higher in P. marmoratus and fecundity was directly related to body size for the two crabs. Size structures differed between studied locations showing size restrictions for specific size-classes. Females from both species remained ovigerous for about 5 months, with P. transversus (May–August) started 1 month after P. marmoratus. Larger sized females displayed higher fecundities. The recruitment of juveniles lasted 5 months for both P. marmoratus (December–May) and P. transversus (November–April). Our results showed that niche partitioning occurred between the two species, where P. marmoratus starts incubating earlier than P. transversus while young of the year of the latter settle earlier on the reefs, taking advantage of convenient seawater temperatures and thus minimizing competition. This study shed some light on the populations of grapsid crabs living in the eastern Mediterranean and provided baseline information on the biology and ecology of the two congeneric shore crabs and their interactions.

The network of roots and rhizomes of seagrasses plays an important role in coastal ecosystems by anchoring the substrate firmly, controlling the biogeochemistry of the sediments and providing habitat for many infaunal organisms. The purpose of this study was to compare five seagrass communities in southern Thailand in terms of species composition, belowground biomass, redox potential and the abundance of the dominant bivalve Pillucina vietnamica. The communities of Halophila ovalis, Cymodocea rotundata, Thalassia hemprichii, H. ovalis with C. rotundata and C. rotundata with T. hemprichii were studied. Belowground biomass, redox potential, bivalve abundance and bivalve size differed among communities and depths (P < 0.05). The redox potential in vegetated areas was lower than in bare sand, showing that seagrass roots trapped more organic matter than did bare sand. The lowest redox potential was in a monospecific patch of the branching root species, C. rotundata. The abundance of P. vietnamica in vegetated areas was lower than in bare sand (P < 0.05). Pillucina vietnamica was relatively large in size in the monospecific stands of C. rotundata and T. hemprichii, where relatively high root biomass and belowground biomass, respectively, were found. Our results suggest that seagrass promotes anoxic conditions belowground by trapping sediment but could obstruct the burrowing activity of lucinids, as dense populations of lucinids occurred mainly in bare sand. However, seagrass also provided shelter for lucinids, as larger bivalves were found in seagrass areas. The interactions among belowground seagrass parts, the biogeochemistry of sediments and the lucinids are highly complex and merit further study.