Swimming propagules (embryos and larvae) are a critical component of the life histories of benthic marine animals. Larvae that feed (planktotrophic) have been assumed to swim faster, disperse farther and have more complex behavioural patterns than non-feeding (lecithotrophic) larvae. However, a number of recent studies challenge these early assumptions, suggesting a need to revisit them more formally. The current review presents a quantitative analysis of swimming speed and body size in planktotrophic and lecithotrophic propagules across five major marine phyla (Porifera, Cnidaria, Annelida, Mollusca and Echinodermata). Results of the comparative study showed that swimming speed differences among ciliated propagules can be driven by taxonomy, adult mobility (motile vs sessile) and/or larval nutritional mode. On a phylogenetic level, distinct patterns emerge across phyla and life stages, whereby planktotrophic propagules swim faster in some of them, and lecithotrophic propagules swim faster in others. Interestingly, adults with sessile and sedentary lifestyles produce propagules that swam faster than the propagules produced by motile adults. Understanding similarities and differences among marine propagules associated with different reproductive strategies and adult lifestyles are significant from ecological, evolutionary and applied perspectives. Patterns of swimming can directly impact the dispersal/recruitment potential with incidence on the design of larval rearing methods and marine protected areas.

The susceptibility of marine bacterial communities to copper pyrithione (CuPT2), zinc pyrithione (ZnPT2) and their degradation product is described and toxicities of these relatively new antifouling biocides compared with those of their harmful organotin (OT) predecessors, tributyltin (TBT) and triphenyltin (TPT). These biocides were added to agar at concentrations of 0, 0.01, 0.1, 1 and 10 mg l−1 and coastal seawater including indigenous bacteria added to each batch of agar solution. The number of bacterial colony forming units (CFU) was measured after 7 days culture. Relative CFU (as a percentage of control) was more than 80% at a concentration of 0.01 mg l−1 of each compound, except for TBT. Relative CFU decreased as a function of dose of each biocide, although concentration-dependent changes in rate of CFU were relatively low during exposure to degradation products of CuPT2 and ZnPT2, pyridine N-oxide (PO) and pyridine-2-sulphonic acid (PSA). Based on comparisons of EC50, TBT was the most bacterio-toxic of the tested compounds (0.2 mg l−1), marginally more so than CuPT2 (0.3 mg l−1). Interestingly, EC50 values of degradation products of CuPT2 and ZnPT2, 2-mercaptopyridine N-oxide (HPT) and 2,2′-dithio-bispyridine N-oxide (PT2) were 0.8 and 0.5 mg l−1, respectively, lower than that of the parent chemical, ZnPT2 (1.4 mg l−1). The EC50 of PT2 was also lower than that of TPT (0.7 mg l−1), implying higher toxicity. Given the overlapping toxicity ranges, these results suggest that marine bacterial communities experience comparably high susceptibility to metal PTs and OTs during their life history.

In this study, polyploidy level was determined by flow cytometry analysis. The effect of polyploidy by colchicine treatment was examined on the growth parameters, malondealdehyde (MDA), as well as activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in response to different levels of salinity in Dunaliella salina. The results of algal growth indicated that 3 M NaCl was the optimal concentration of salt, since the highest enhancement in fresh and dry weight, chlorophyll and carotenoids, soluble sugar, glycerol, protein and starch content was observed in comparison to other concentrations. The amount of these metabolites declined in the concentrations under optimum salinity. The least and highest amounts of MDA were observed at 1 and 4 M NaCl respectively. Polyploidy in optimum concentration of salt, caused further increment of the above growth parameters. In relation to this, in most cases, treatment of 0.1% colchicine was most effective. The beneficial effects of polyploidy in non-optimal conditions were also found in some parameters such as biomass, chlorophyll, carotenoids, proteins and starch. Furthermore, the activity of antioxidant enzymes CAT, SOD and POD showed a positive significant correlation with salt stress and these were maximized at 4 M NaCl. Polyploidy (especially colchicine 0.1%) affected activity of these antioxidant enzymes in some concentrations of salt. Overall, our results suggest that the microalgae has significantly different responses to salt stress based on ploidy levels.

This study was conducted in February, April and June 2009 at three stations in the southern Adriatic. Occurrence of the dinoflagellate Noctiluca scintillans and tunicates Salpa fusiformis and Salpa maxima in high abundances for the oligotrophic open sea, indicates the importance of physical forcing (vertical mixing) and inflow of nutrient-enriched Atlantic water, due to the Bimodal Oscillating System (BiOS) mechanism, into the Adriatic Sea thus creating an environment favourable for their rapid increase. This is the first time a bloom of N. scintillans has been recorded in the open southern Adriatic (OSA). High abundance of Noctiluca and salp populations in the OSA was characterized by low abundance of phytoplankton and other zooplankton, with obvious trophic implications (reduction of food availability to crustacean primary consumers). Moreover, during the S. maxima bloom in June 2009, calanoid copepods and appendicularians were almost completely absent (<1 ind. m−3).

In the Rio de la Plata salinity, temperature, chlorophyll a (chl a), and densities (ind. m−3) of the copepods Acartia tonsa and Paracalanus parvus were measured from January to November in 2003 by following a nested weekly and monthly design. Such sampling yielded two separate datasets: (i) Yearly Dataset (YD) which consists of data of one sampling effort per month for 11 consecutive months, and (ii) Seasonal Weekly Datasets (SWD) which consists of data of one sampling effort per week of any four consecutive weeks within each season. YD was assumed as a medium-term low-resolution (MTLR) dataset, and SWD as a short-term high-resolution (STHR) dataset. The hypothesis was, the SWD would always capture (shorter scales generally captures more noise in data) more detail variability of copepod populations (quantified through the regression relationships between temporal changes of salinity, temperature, chl a and copepod densities) than the YD. Analysis of both YD and SWD found that A. tonsa density was neither affected by seasonal cycles, nor temporal variability of salinity, temperature and chl a. Thus, compared to STHR sampling, MTLR sampling did not yield any further information of the variability of population densities of the perennial copepod A. tonsa. Analysis of SWD found that during summer and autumn the population densities of P. parvus had a significant positive relationship to salinity but their density was limited by higher chl a concentration; analysis of YD could not yield such detailed ecological information. That hints the effectiveness of STHR sampling over MTLR sampling in capturing details of the variability of population densities of a seasonal copepod species. Considering the institutional resource limitations (e.g. lack of long-term funding, manpower and infrastructure) and the present hypothesis under consideration, the authors suggest that a STHR sampling may provide useful complementary information to interpret results of longer-term natural changes occurring in estuaries.

The colonization features of ciliate communities have proved to be a useful tool for indicating water quality status in aquatic ecosystems. To determine an optimal water depth for bioassessment using these ecological bioindicators, the colonization process of periphytic ciliates was studied at four depths of 1, 2, 3.5 and 5 m in Chinese coastal waters. Samples were collected at time intervals of 3, 7, 10, 14, 21 and 28 days using glass slides. The periphytic ciliate communities represented similar colonization dynamics from a depth of 1 to 3.5 m: (1) the temporal variability was well fitted to the MacArthur-Wilson and logistic models; (2) the species composition reached an equilibrium during the exposure time periods of 10–14 days; and (3) the maximum abundances were definitely higher at a depth of 1 m than those at 3.5 m. PERMANOVA test revealed that the colonization pattern at 1 m depth was significantly different from those at the other three depths. Results suggest that the colonization dynamics of periphytic ciliates may be influenced by water depth in coastal waters. These findings provide an important reference for establishing an optimal sampling strategy for bioassessment on large spatial/temporal scales in marine ecosystems.

A massive die-off of benthic suspension feeders (BSF) covered by large amounts of sediments was observed along Prince Islands coasts (north-eastern Sea of Marmara) in August 2015. Alcyonarians, pennatulaceans, bivalves and sponges were severely affected. Many BSF probably died from burial and clogging of their feeding and respiratory apparatus. Of the gorgonian colonies, 66 ± 34% (mean ± SD) were dead, while 15 ± 16% (mean ± SD) displayed recent necrosis on the colony surface. In addition, histopathological and microbial examinations of the affected gorgonians and gold corals (Savalia savaglia) suggest that stress caused by sedimentation made them vulnerable to exploitation by consistently isolated opportunistic microorganisms. We isolated Vibrio splendidus and Vibrio neptunius from diseased gold coral colonies, but the bacterial isolates obtained from gorgonians could only be identified to genus Vibrio level. The presumably artificially introduced fungus Mucor circinelloides was common on both gold coral and gorgonians. This mould and opportunistic bacteria may have colonized BSF by taking advantage of low oxygen levels leading to impaired coral immune responses and thereby exacerbated the BSF mortality. Construction and landfill operations at Yassıada seem to be the greatest contributor to the observed sedimentation, as shown by silicate concentrations in nearby waters. These observations imply that preventive measures are necessary when construction operations take place in the vicinity of sensitive marine habitats.

Edwardsiidae is one of the most speciose families within order Actiniaria with ~75 valid species of burrowing sea anemones. Five edwardsiids have been recorded in South Atlantic waters with only two species known for Brazil: Nematostella vectensis and Edwardsia migottoi. Such low diversity is probably the result of a historical small number of specialists in the region combined with difficulties in collecting and identifying these small burrowing animals. Although edwardsiids have been reported from Brazil since at least the 1960s, these reports did not include proper descriptions or specific identification, making comparison to other valid species impossible. Here we describe a new genus, Isoscolanthus gen. nov., and two new species: Isoscolanthus iemanjae sp. nov., Isoscolanthus janainae sp. nov. and we also describe Scolanthus crypticus sp. nov., the first species of the genus for Brazil. Isoscolanthus gen. nov. is easily distinguished from other edwardsiid genera by a combination of external (i.e. presence of periderm and nemathybomes in proximal end and 12 tentacles), microanatomical (i.e. four microcnemes) and cnidom features (i.e. pterotrichs in nemathybomes). In addition to the description of the new genus and species, we expand the range distribution of Nematostella vectensis and Edwardsia migottoi in the South-western Atlantic. The number of edwardsiids known from Brazil is raised from two to five species, substantially increasing the diversity of soft-bottom sea anemones for South Atlantic waters.

The present study describes the variation in the benthic macrofauna related to the presence of Sabellaria wilsoni (Polychaeta: Sabellariidae) reefs on a sandy beach of the Brazilian Amazon Coast. The study also investigated whether the erosion of parts of the reef by intense wave action results in differences in the fauna. Samples were collected from a patch of reef and the adjacent sandy sediment for the analysis of the zoobenthos and substrates (granulometry and organic matter content) on Algodoal-Maiandeua Island (northern Brazil coast). The reef had more heterogeneous sediments and a higher organic matter content, and its fauna was distinct from that of the beach, with a higher density, species richness and diversity. The reef fauna included taxa typical of both consolidated and unconsolidated substrates. The portion of the reef more exposed to wave action had a lower density of reef-building worms, and these worms were smaller in size than those of the more protected portion, although the associated fauna of the exposed portion was denser and richer in species. These results confirmed that S. wilsoni is an important ecosystem engineer on the Amazon coast, and that the diversity and unique features of the fauna associated with these reefs emphasize their importance as a substrate for the local benthic communities, in particular in areas where consolidated bottoms are naturally scarce.

The horse mussel Modiolus barbatus is a marine benthic bivalve, distributed mainly in the Mediterranean basin, that constitutes a fishery product of high economic importance and a promising candidate for aquaculture. The current study provides the first insights regarding the genetic profile of M. barbatus populations from the eastern Mediterranean, by analysis of a partial segment of the mitochondrial COI gene in individuals collected from five sampling localities within the Aegean Sea. To the best of our knowledge, the derived haplotypes represent the first DNA barcodes of M. barbatus from the entire Mediterranean region. Maximum likelihood phylogenetic analysis revealed that M. barbatus from the North Sea and M. barbatus from the eastern Mediterranean may not belong to the same species and as a consequence, there might be three species of the genus Modiolus in Europe. On the other hand, eastern Mediterranean M. barbatus haplotypes were found to be more closely related to the Asian-Pacific Modiolus species. All geographic populations analysed displayed high levels of genetic diversity, in terms of haplotype and nucleotide diversity and a considerable number of unique alleles. Divergence among populations was found at generally low levels, corresponding with the majority of pairwise Fst values not being significant. These findings suggest no population structure and high levels of gene flow, a common feature observed in marine bivalves with long pelagic larval phases.

Various herbivorous invertebrates in seagrass beds are considered to be generalists in food use and their diets may temporally fluctuate according to the availability of food sources. We assessed whether food sources of herbivorous gastropods vary in a subtropical seagrass bed in Nagura Bay, Ishigaki Island, where coexisting seaweeds grow densely in spring but minimally in summer. Abundant gastropods and their possible food sources were collected in spring and summer of 2013 and 2015, and their stable carbon and nitrogen isotope ratios were measured. Between the two seasons, each possible food source had similar isotopic values, but all the herbivorous gastropod species in summer were more enriched in 13C than the gastropod samples in spring. The mixing models in SIAR (Stable Isotope Analysis in R) showed that the total contribution rates of seaweeds, i.e. rhodophytes, phaeophytes and chlorophytes, for all herbivorous gastropod species decreased from spring to summer; in contrast, the contribution rate of seagrasses increased. Linear Mixed Models showed that the seasonal variation in δ13C of the herbivorous gastropods was larger than that of the possible food sources, adding further evidence to the seasonal change in food sources of the herbivorous gastropods. This seasonal change in food use appears to correspond to the change in seaweed biomass, suggesting that herbivorous gastropods flexibly change their diets depending on food availability.

Thyone and Havelockia are worldwide-distributed genera represented in the Western Atlantic by eight and three species, respectively. In this paper, we describe two new shallow-water species from the Brazilian coast: Thyone waltinhoi sp. nov. and Havelockia oraneae sp. nov. These genera are very similar morphologically but the presence of subdivisions in their calcareous rings separates them into different families, Thyone in Phyllophoridae and Havelockia in Sclerodactylidae. To observe the presence of subdivisions, we submerged the calcareous rings in an iodine solution prior to morphological analyses. Thyone waltinhoi sp. nov. differs from its Western Atlantic congeners in its dermal ossicles and Havelockia oraneae sp. nov. differs from its South-western Atlantic congeners in the composition of its introvert ossicles. In addition to species descriptions, illustrations and morphological diagnoses of both genera are provided, along with a synoptic table of their Western Atlantic species, and a discussion of the taxonomic significance of the dermal ossicles and the calcareous ring.

The effects of trampling are usually confounded by the diffuse impacts of the urbanization of sandy beaches. We performed a controlled experiment on a beach with low visitation rates to test the hypothesis that ghost crabs avoid building their burrows on impacted plots as a result of the compacted sediment, and they migrate to non-trampled areas. The sampling design encompassed 11 survey quadrats (6 × 6 m) above the strandline, including five trampled plots (100, 300, 900, 1500 and 3000 steps) and six non-trampled plots. The plots were sampled before and after 24, 48 and 72 h of experimental trampling. We found that the ghost crabs avoided building their burrows in only the 1500× and 3000× trampled plots after 24 h, but the avoidance was not related to sediment compactness. Additionally, the emersion time and escape distance from humans were significantly delayed in the most trampled plots, suggesting a lower surface activity and an avoidance of irregular (i.e. high micro-relief) sediment surfaces by ghost crabs, which might reduce their ability to perceive potential predators.

After the recent detection, by both morphology and DNA barcodes, of the larval stages of an unknown species of pea crab (Pinnotheres sp.) in European waters, adults of this crab are herein reported and described as a new species. The current known geographic distribution of the species comprises the Gulf of Cádiz in the eastern Atlantic and the adjacent Mediterranean waters of the south of the Iberian Peninsula (Alboran Sea), where this crab is well-established inside the anomiid bivalve Anomia ephippium. In the Gulf of Cádiz, the species displayed a relatively high prevalence: on average, 55.6–77.7%, in A. ephippium samples. The dominant demographic categories of the new species were soft females (61.8–77.0%) with fewer males (17.7–21.10%). Most of the host bivalves carried only one crab; in bivalves harbouring two crabs, heterosexual pairs were collected more frequently than expected by chance, which suggests that they could be mated pairs. A strong correlation between host size and soft female size was found (r = 0.73, P < 0.01) indicating that space availability within hosts seems to be relevant in determining the size of the sedentary phase of the new crab species.

The brush-clawed shore crab Hemigrapsus takanoi is a native species from the Western Pacific and an invader of the European Atlantic coast from northern Spain to southern Denmark. Despite the increasing concern about its rapid expansion, little is known about the early stages in its life history. In the present study, the larval morphology of H. takanoi is described and illustrated from specimens obtained in the laboratory from its type locality, Tokyo Bay, Japan. Its larval development follows the pattern of Varunidae, that involves five zoeae and one megalopa. The morphological characters of the larvae of H. takanoi are compared with those of the other known Hemigrapsus species of the North Pacific. In addition, to facilitate an early detection of the invasive species of Varunidae inhabiting European Atlantic waters, a summary of the key characters to identify their larval stages is included.

Hermit crabs use different senses to search for and find shells. In most cases, chemical cues have been proven to act as a very efficient way of finding new shells. However, in intertidal environments, the water transports chemical signals in different directions and velocities may make it harder to track the source of the cue, so visual stimuli may be a more precise source of information. The hermit crab Calcinus californiensis shows a preference for the biconical shells of Stramonita biserialis, although the crabs may also use the less preferred shell of Nerita scabricosta. We were interested in exploring if C. californiensis identify the preferred shell species through vision in the absence of chemical stimuli. We presented both shell species to hermit crabs in two different sets of experiments. In one experiment, we presented to the hermit crabs real shells of N. scabricosta and S. biserialis, and in another, we presented only the silhouettes of the same shells. The hermit crabs discriminated between the real shells and the silhouettes of N. scabricosta and S. biserialis. Females attended with higher frequency to real shells and silhouettes of S. biserialis; while males attended more to shells and silhouettes of N. scabricosta. Although, larger males biased their attendance toward shells of S. biserialis. Our results show that visual perception may be more important than we have thought in intertidal animals.

Where two species occupy the same habitat and similar niches, competition is likely to drive small-scale spatial niche separation or resource partitioning that may not be immediately apparent. A stable isotope approach was used to investigate potential trophic niche separation between co-existing rocky shore crabs in the North-West (NW) Arabian Gulf. Leptodius exaratus and Pilumnopeus convexus which occupy similar shore height on the same rocky intertidal habitats. We also investigated conspecific differences between males vs females and adults vs juveniles. δ15N results indicated that adults of both species occupy a high trophic level in the rocky shore community, suggesting similar functional roles and potential for competition for food resources, while significant differences in δ13C values indicated differences in dietary sources between the two species, and also changes in diet between juveniles and adults in both species. MixSIAR analysis of δ15N and δ13C data confirmed field observations that both species are generalist omnivores, with potential for direct competition including adult predation on juveniles, including conspecifics. Differentiation in isotopic niches (SIBER analysis) was mainly driven by the significant differences in δ13C values, suggesting that co-existence of the two crab species is at least in part mediated by trophic niche separation or dietary resource partitioning, with some (unquantified) potential for spatial resource partitioning at the microhabitat level.

The phyllosoma larva of spiny and slipper lobsters (Palinuridae and Scyllaridae respectively) can disperse during several months before metamorphosing into a decapodid stage, which is the key phase for a successful settlement. The largest Scyllarus decapodid known to date was recently collected near the Canary Islands and identified by DNA analysis as Scyllarus subarctus. This species had never been previously reported from the area, and the decapodid stage is described here for the first time. The examination of further museum specimens has now significantly expanded the current distribution of S. subarctus, including much of the NW African coast, St Helena and Canary Islands. These results highlight the importance of combining molecular analysis of recently collected specimens with historical collections.

Recent studies have shown that anguillid eel populations in habitats spanning the marine–freshwater ecotone can display extreme plasticity in the range of catadromy expressed by individual fish. The apparent use of marine and freshwater habitats by the European eel Anguilla anguilla was examined by analysing the strontium (Sr) and calcium (Ca) concentrations in otoliths of eels collected from a tidal Atlantic lake system in Ireland. Variations of the Sr:Ca ratio in the otoliths indicated that a variety of environmental salinities had been experienced in the habitats that were occupied during the growth phase of these individuals in the tidal Atlantic lake system. The otolith microchemistry of these eels indicated that most of the eels had entered each salinity environment (freshwater (FW); brackish water (BW); marine-dominated water (MW) and full seawater (SW)) from fresh water to full seawater just after recruitment and had stayed in each environment until maturation without movement to other salinity environments. Only 2 of 93 (2%) eels had shifted their habitat once in their lives. This result suggests that each individual might have an environmental habitat preference, although each individual could move along a short (<2 km) salinity gradient.