Genetic connectivity directly shapes the demographic profile of marine species, and has become one of the most intensely researched areas in marine ecology. More importantly, it has changed the way we design and describe Marine Protected Areas across the world. Population genetics is the preferred tool when measuring connectivity patterns, however, these methods often assume that dispersal patterns are (1) natural and (2) follow traditional metapopulation models. In this short review, we formally introduce the phenomenon of cryptic dispersal, where multiple introductory events can undermine these assumptions, resulting in grossly inaccurate connectivity estimates. We also discuss the evolutionary consequences of cryptic dispersal and advocate for a cross-disciplinary approach that incorporates larval transport models into population genetic studies to provide a level of oceanographic realism that will result in more accurate estimates of dispersal. As globalized trade continues to expand, the rate of anthropogenic movement of marine organisms is also expected to increase and as such, integrated methods will be required to meet the inevitable conservation challenges that will arise from it.

Harmful algal blooms caused by raphidophyte species of the genus Chattonella (i.e. Chattonella antiqua, Chattonella marina and Chattonella ovata) have been documented in temperate coastal regions around the world. To understand the effects of physicochemical factors on bloom development of Chattonella spp., we investigated the variations of vegetative and resting cells (i.e. cysts) of Chattonella spp. and environmental variables in two coastal environments, Uranouchi Inlet (extremely closed) and Nomi Inlet (semi-closed), with contrasting enclosed natures. Although the vegetative cells and cysts of Chattonella spp. were distributed in both coastal regions, the densities were remarkably higher in Uranouchi Inlet than in Nomi Inlet. The mud content in the sediments of Uranouchi Inlet was also higher than that in the sediments of Nomi Inlet, meaning that fine particles such as cysts are likely to accumulate in the former region. Because of the extremely closed nature of Uranouchi Inlet, warm oceanic waters of the Kuroshio Current penetrate the inlet only infrequently. These results suggest that the closed nature of coastal regions is an important factor influencing either water exchange or the resultant accumulation of Chattonella cells in coastal environments.

It has increasingly been recognized that defence of microalgae against predator grazing is a passive response to increase algal population density by excreting chemicals with a change in physical properties. As common biological pollutants in the cultivation of the microalgae, the community-based method was used to identify the ability of two microalgae, Chlorella sp. and Nannochloropsis oceanica, to defend against protozoan grazing. Mature protozoan samples with 14-day age were collected, using microscopy glass slides, in coastal waters of the Yellow Sea, northern China. For both microalgae, a gradient of concentrations was designed as 100 (control), 104, 105, 106 and 107 cell ml−1, respectively. Results showed that both test algal species represented strong defence effects on protozoan grazing, especially at high density levels. Species richness, abundance and taxonomic distinctness of the protozoan assemblages showed a sharp decrease at high concentration level (107 cell ml−1) of both algae. A significant variation in protozoan community structures was found to be driven by the gradient of the algal concentrations. The paired taxonomic distinctness indices of the protozoan communities showed an increasing trend of departure from the expected taxonomic pattern with increase of algal concentrations. Based on the results, we suggest that the community-based bioassay might be used as a feasible tool for identifying defence against protozoan grazing of microalgae.

To evaluate the effects of different anthropogenic activities on zooplankton and the pelagic ecosystem, we conducted seasonal cruises in 2010 to assess spatial heterogeneity among the mesozooplankton communities of Xiangshan Bay, a subtropical semi-enclosed bay in China. The evaluation included five different areas: a kelp farm, an oyster farm, a fish farm, the thermal discharge area of a power plant, and an artificial reef, and we aimed to identify whether anthropogenic activities dominated spatial variation in the mesozooplankton communities. The results demonstrated clear spatial heterogeneity among the mesozooplankton communities of the studied areas, dominantly driven by natural hydrographic properties, except in the area near the thermal discharge outlet of the power station. In the outlet area, thermal shock caused by the discharge influenced the mesozooplankton community by decreasing abundance and biomass throughout the four seasons, even causing a shift in the dominant species near the outlet during summer from Acartia pacifica to eurythermal and warm water taxa. Unique features of the mesozooplankton community in the oyster farm may be due to the combined effects of oyster culture and the natural environment in the branch harbour. However, kelp and fish culture, and the construction of an artificial reef did not exert any obvious influence on the mesozooplankton communities up to 2010, probably because of the small scale of the aquaculture and a time lag in the rehabilitation effects of the artificial reef. Thus, our results suggested that the dominant factors influencing spatial variations of mesozooplankton communities in Xiangshan Bay were still the natural hydrographic properties, but the thermal discharge was an anthropogenic activity that changed the pelagic ecosystem, and should be supervised.

Canopy-forming fucoid algae have an important role as ecosystem engineers on rocky intertidal shores, where they increase the abundance of species otherwise limited by exposure during low tide. The facilitative relationship between Ascophyllum nodosum and associated organisms was explored using a frond breakage experiment (100%, 50%, 25%, 0% intact-frond treatments) in southern England, to assess the consequences of disturbance. Understorey substratum temperature was on average 3°C higher in 0% and 25% intact-frond treatments than in plots with 50% and 100% intact fronds. Light (as PAR during low tide) doubled in 0% intact-frond treatments in comparison to other treatments (which had similar light levels). Mobile invertebrate species richness declined by on average 1 species per m2 in the treatments with only 25% and 0% intact fronds, and the abundance of Littorina obtusata declined by 2.4–4.2 individuals per m2 in the treatments with 25 and 0% intact fronds. Sessile taxa, including Osmundea pinnatifida and encrusting coralline algae, declined by half on average in the 0% intact-frond treatment. These results suggest that the ability of Ascophyllum to mediate environmental conditions to the understorey is the mechanism responsible for species distributed in the understorey (autogenic ecosystem engineering). The results of this study imply that a pulse disturbance resulting in a 50% breakage of Ascophyllum fronds significantly increases temperature and decreases the abundance of mobile invertebrates usually associated with Ascophyllum. Sessile taxa associated with Ascophyllum can, however, withstand disturbances down to 25% intact Ascophyllum fronds.

Beach ecosystems extend from dune to offshore areas along most coasts, and provide essential services that are not provided by any other ecosystem. Indeed, sandy systems contain unique biodiversity and supply nursery and foraging areas for numerous commercially important marine species, such as flatfish. However, these systems are threatened by increasing anthropogenic pressure. Green tides (GT, i.e. accumulations of green opportunistic macroalgae) are a major human-induced threat to marine ecosystems, from inshore to nearshore. This eutrophication process greatly affects both benthic invertebrate communities and flatfish communities, within sheltered and non- or microtidal systems. However, the responses of dynamic open macrotidal sandy systems to eutrophication in the form of macroalgal mats are not yet fully understood. In particular, understanding the effects of GT on two connected biological compartments (infauna and flatfish) within two connected habitats (intertidal and subtidal) is crucial. Here, we set out to assess the influence of several environmental variables, including Ulva biomass, on the variability in infauna and flatfish communities in both the intertidal and the subtidal at four sites impacted or not by GT. In total, 110 biodiversity samples were analysed with classic and novel analytical approaches. Our results demonstrate that the presence of GT specifically impacts intertidal macroinvertebrate communities. However, small effects of GT on subtidal infauna communities, as well as on species-specific flatfish at both intertidal and subtidal, were still detectable. Our findings underline the vulnerability of highly dynamic ecosystems exposed to anthropogenic stress, in particular intertidal sandy shores.

The present study describes the morphological changes of the mouthparts and foregut of the freshwater prawn M. acanthurus that occur during the development of the larvae and first juvenile. The results indicate that the zoeae I have mouthparts with reduced setae and a structureless foregut that indicates obligatory lecithotrophic behaviour. There is an increase in the number of setae in these structures between the zoea II and the juvenile stage, indicating the adaptation of the organism for feeding. More complex structural alterations were observed in the first juvenile, which acquires benthonic habits, which ensure the capture and ingestion of a diversity of feeding resources found in the substrate.

The population parameters of mantis shrimp (Squilla mantis Linnaeus, 1758) were studied regarding age composition, sex ratio, growth, survival and mortality rates, and the exploitation rate in the Aegean coasts of Turkey in 2013. We collected 936 specimens by shrimp gillnets along the coasts of Izmir Province from April to October 2013. The mean condition factor was K = 1.02 for both sexes, while the sex ratio was 58.7% for female and 41.3% male. Mean lengths, mean weight and length–weight relationship were calculated as TL = 12.57 ± 0.07 cm, CL = 3.02 ± 0.02 cm, W = 22.14 ± 0.37 g, W = 0.0098 × L3.02. Age determination was based on indirect ageing through length–frequency data using the Bhattacharya method. The age of the population varied from 0+ to 3+. Von Bertalanffy growth parameters were estimated as TL∞ = 19.69 cm, CL∞ = 4.74, W∞ = 79.41 g, k = 0.50 year−1 and t0 = −0.37 year. Mortality and exploitation rates derived as Z = 1.90, M = 1.16, F = 0.74 and E = 0.39, respectively.

The present study investigated the population dynamics of Exhippolysmata oplophoroides in an area influenced by upwelling, focusing on reproductive period, sex ratio, growth rate, longevity, mortality, relative growth and size of sex change. We also tested the hypothesis that the appendices internae increased in size with sex change from the male to the simultaneous hermaphrodite phase as possible replacements for the male appendices masculinae, which are reduced or lost at sex change. Population structure was assessed by the distribution of size frequency in three demographic groups: male phase, hermaphrodite phase with, and without embryos. For relative growth analysis, the length of the following structures was measured: carapace, second pleuron, first pereopod, second pereopod, appendices internae of the second to fifth pleopods, and appendix masculina. Smaller size classes were composed only by male-phase individuals. The sex ratio was significantly biased towards the simultaneous hermaphrodite phase. Reproduction was continuous in the population throughout the year. Slower growth rates but higher maximum body sizes than those estimated at other locations in south-eastern Brazil were observed in the population studied. Cooler temperatures and higher nutrient levels associated with upwelling may have produced this pattern of reproduction and growth, similar to that found in more southerly austral latitudes. We also found that sex change influences the relative growth of body structures such as the second pereopods, appendices internae, and appendix masculina, and hypotheses on the adaptive value of such allometric growth are proposed.

Nymphonella tapetis (Pycnogonida, Ascorhynchidae) is an endoparasitic sea spider affecting bivalves. Recently, sea spiders have been found on a massive scale in the commercially important Manila clams (Veneridae, Ruditapes philippinarum) in Japan (Tokyo Bay). Simultaneously, mass mortality has occurred in this area. Local fishers assumed that this mass mortality was caused by the parasitic sea spider, despite the effect of the parasite and parasite intensity on the host being unknown. To evaluate the susceptibility of the Manila clam to sea spider infestation and the impact on mortality levels, we established six treatments at different infection intensities (density of newly hatched larvae of sea spiders) over a 6-month long laboratory experiment. We monitored mortality and three susceptibility indices (clearance rate, sand-burrowing speed and adductor muscle strength) under sufficient food conditions. Parasitization by sea spider affected clearance rate and sand-burrowing speed. The pattern of parasitic intensity effects on survival of Manila clam hosts was shown to be dependent on the levels of parasite numbers, i.e. clams with lower parasitic levels (total of <200 hatching larvae of sea spider given to a host) have a higher survival rate, and high mortality of host clams was shown in excessively higher parasitic densities (400–4000 individuals). Such pattern of parasitic effects on host survival might be one of the causes of mass mortality of Manila clams occurring in the field.

The sabellariid worms are important ecosystem engineers in coastal zones, due to their ability to construct sand reefs, modify environments and structure biological communities. This article describes the reproductive biology of Sabellaria wilsoni on a beach of the Amazon coast. Each month between May 2008 and April 2009, specimens were collected for morphometric and histological analyses for sexing and determination of gonadal maturity. In females, the number and diameter of the oocytes at different stages of vitellogenesis were also recorded. The results showed that the species is dioecious, with sexual reproduction, females larger than males, and a female-biased sex ratio (overall, 1.6♀: 1♂). Four distinct stages of gonadal maturation were identified in the males and females – (i) initial development, (ii) maturing, (iii) mature and (iv) spawning. Sexual maturity is attained rapidly, and reproduction is continuous, with two breeding peaks, one in the dry season, related to the increased intensity of hydrodynamic conditions and reef erosion; and the other in the rainy season, when the availability of space and nutrients increases. The reproductive strategy of the species reinforces the classification of the sabellariids as r-strategists, adapted to colonize habitats with unstable environmental conditions.

A collection of more than 1500 specimens of Syllidae (Annelida, Polychaeta) from sub-Arctic and Boreal regions along the coast of Norway has been studied. We report 32 species, two of them new to science, belonging to the genera Sphaerosyllis Claparède, 1863 and Syllis Savigny in Lamarck, 1818, and 16 new to Norway. Sphaerosyllis tarquei sp. nov. is characterized by having long blades on its compound chaetae and the presence of glands inside the dorsal cirri. Syllis kas sp. nov. was reported, figured and described by Uschakov (1955) as Syllis oerstedi (Malmgren, 1867); however, revision of the types of Chaetosyllis oerstedi reveals that they are sexual stolons of Syllis cornuta Rathke, 1843; this species is characterized by the shape of the spiniger-like chaetae, which are relatively short, distally blunt, with a thin distal spine, and unidentate falcigers some of which have similar spines. We also include descriptions and figures of Parexogone longicirris (Webster & Benedict, 1887) and Syllides longocirrata Ørsted, 1845. Finally we include a key of all reported species in the area.

Genetic diversity and population distribution are influenced by environmental factors, yet information is scarce on the interrelations that define dispersal of populations. Transitional water ecosystems are hosting habitats with temporally and spatially variable conditions, which make them very useful in understanding the mechanisms affecting population establishment. For the study, seasonal samples were collected from four lagoons in the lagoonal complex of Amvrakikos Gulf (W Greece). The mitochondrial DNA (COI gene) was analysed from polychaetes of Nephtys hombergii, as it is considered an important component of these assemblages and shows great dispersal ability. The results of the genetic analysis showed intraspecific variability in all the lagoons, with genetic structuring tending to follow a seasonal pattern rather than a spatial one. The results of BIOENV analysis indicated correlation of the observed pattern with the water pH levels, the redox potential and the concentration of phosphate in the sediment. The complexity of the network suggested the enhancement of the local population with more recently established haplotypes. The findings of the study support the necessity of designing management strategies by taking into account genetic diversity and population demography approaches in addition to those based on species and habitats.

Christmas tree worms (Spirobranchus spp.) are prominent sessile organisms inhabiting hermatypic corals in tropical and sub-tropical reefs. Until recently, most of the larger Spirobranchus species were considered to be in obligatory associations with live hermatypic corals. However, recent studies indicate that some Spirobranchus species can build tubes on artificial substrate as well and that others may show preferences for using specific species of corals and hydrozoans as substrates. In the present study, we conducted a survey of Spirobranchus spp. substrate preference in the Gulf of Eilat. We found seven morphotaxa of Spirobranchus, of which two may be a single new species. We show that Spirobranchus taxa differ not only in their morphology, but also in their substrate use. Our results demonstrate that the ecological niche of Spirobranchus is species-specific, and a putative innate preference exists for some substrates.

Two new species of free-living marine nematodes, Litinium dispariseta sp. nov. and Wieseria minor sp. nov. are described from an abyssal plain with a water depth of 4117–5035 m near the Southern Kyushu-Palau Ridge in the tropical Western Pacific Ocean. Litinium dispariseta sp. nov. is characterized by having distinct inner labial setae two times longer than the outer labial setae, wrench-like amphideal foveas, a single preanal midventral supplementary seta and a short cylindrical tail with bluntly rounded tip. It differs from congeners by its distinctly long inner labial setae relative to the outer labial setae (two times longer vs shorter or equal in length) and peculiar wrench-like amphideal foveas (vs horseshoe shaped or ovoid with round to oval anterior aperture). Wieseria minor sp. nov. has a clavate tail, a character found only in the four congeners W. glandulosa (Kreis, 1929), W. longiseta (Allgén, 1947), W. clavata Gerlach, 1956 and W. inaequalis Gerlach, 1956. However, Wieseria minor sp. nov. differs from these congeners by its much smaller body size (1045 µm vs 2120–3125 µm) and oblong amphideal foveas with double contour (vs a single oblong or ovoid loop). An emended diagnosis for Wieseria and pictorial keys for Litinium and Wieseria are provided.

The increasing human impact at shallow depths may be affecting the Mediterranean endemic coral Astroides calycularis irreversibly. Therefore, management tools need to be developed for use in its conservation. The main aim of this study was to test a reliable attachment methodology for restoring sites where the species has been affected by human activities. We chose an attachment technique using a marine quick-action epoxy resin, completing three treatments (control, transplanted and translocated colonies) in two sites with different hydrodynamic conditions. Control colonies were undisturbed colonies that were not manipulated; translocation colonies were dislodged and reattached in the same place; and transplantation colonies were dislodged and attached in a different area. Translocated colonies showed a higher survival than transplanted ones, and survival was also higher in environments with more hydrodynamism. Regarding growth, Analysis of Variance (ANOVA) did not show significant differences among treatments, but significant differences between areas with different hydrodynamic conditions were noted. This study confirms that it is possible to transplant or translocate colonies of this coral with the technique proposed here, which could be used in future management plans for areas impacted by humans.

In the present study a comparison of the otolith morphology of two species of parrotfish, family Scaridae, collected from the Red Sea coast of Egypt, is conducted to identify the most appropriate taxonomic characters that separate these species. Ontogenetic changes in the otoliths of the two scarid fishes become evident. In the otoliths of Chlorurus sordidus, the following characters are comparable in small-sized adult fishes: otolith width, otolith depth, mesial surface shape, lateral surface shape, shape of sulcus acusticus, column, rostrum and size of rostrum. The otoliths of young adults (GI) C. sordidus differ from the adult ones in 14 out of the 22 characteristics studied. In the otoliths of Hipposcarus harid, the following characters are comparable in small and large fish: otolith width, otolith depth, mesial and lateral surface shapes, shape of sulcus acusticus, rostrum and size of rostrum.

Cleaning interactions between the wrasse Symphodus melanocercus and brown meagre Sciaena umbra are documented from observations whilst free diving on a shallow rocky reef in the central Mediterranean Sea. Cleaning events occurred at cleaning stations mainly during the morning and gradually decreased in the evening. The body parts mostly cleaned were the opercular region and the fins, possibly as gnathiid isopods preferentially attach to these areas.

Several characteristics of Totoaba macdonaldi Perciformes: Sciaenidae, including migratory movements along temperature gradients make it vulnerable to oxidative stress. Oxidative stress can also be associated with reproduction. The objectives of the present study were to examine oxidative stress indicators in liver of totoaba throughout the seasons (spring, autumn and winter), and the associated fluctuations in superficial sea temperature (SST, °C), as well as to evaluate possible variations between sexes and reproductive maturity stages. A total of 173 liver samples from totoaba captured in the Gulf of California, Mexico, were obtained from April 2010 to February 2013. Superoxide radical production (O2•−), lipid peroxidation (TBARS) levels, and activity of antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) were quantified spectrophotometrically. Generalized linear models (GLM) were used to determine which factors contribute to explain O2•− production and TBARS levels. The significant predictive variables were the seasons, which were significant in all applied models, as well as SOD and CAT activities. In general, enzyme activity was higher in immature totoaba; this was not seasonally modified. Low temperatures in winter were associated with high O2•− production and TBARS levels, particularly in totoaba that are not yet reproductively mature. Seasonal changes in sea surface temperature did not affect the oxidative stress indicators in mature totoaba (both males and females); this suggests that mature totoaba are less sensitive to temperature changes from an oxidative stress perspective.