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Este artículo contiene 7 páginas, 3 figuras, 1 tabla., Mediterranean coralligenous outcrops are a biodiversity hotspot where cryptobenthic and epibenthic fish species conform an important proportion of the inhabiting fish assemblages. We investigated the distribution of epibenthic fish assemblages in coralligenous outcrops, the contiguous detritic bottoms and the margin where coralligenous outcrops meet the detritic bottoms in the Columbretes Islands (NW Mediterranean Sea). Our results showed significant differences in the distribution of epibenthic fish. In terms of species diversity, the margin held the same number of species than the coralligenous. However, two species (Gobius kolombatovici and Thorogobius macrolepis) found their habitat almost exclusively in the margin, which was clearly dominated in terms of abundance by G. kolombatovici. On the other hand, detritic bottoms were characterized by a lower number of species. Altogether, the obtained results show the importance of coralligenous outcrops for Mediterranean epibenthic fishes and especially their margin with adjacent detritic bottoms, which holds a characteristic epibenthic fish assemblage., D. K. Kersting was supported by a Juan de la Cierva-Incorporación contract (Spanish Ministry of Science, Innovation and Universities; IJCI_2017-31457) and by the postdoctoral fellowship programme Beatriu de Pinó funded by the Secretary of Universities and Research (Government of Catalonia) and the Horizon 2020 programme of research and innovation of the European Union under the Marie Sklodowska-Curie grant agreement No 801370.

Seagrasses, a polyphyletic group of about 60 marine angiosperm species, are the foundation of diverse and functionally important marine habitats along sheltered sedimentary coasts. As a novel ecological function with high societal relevance, a role of the seagrass leaf canopy for reducing potentially harmful bacteria has recently been hypothesized in tropical regions, but data for temperate regions are lacking. Here, we tested whether or not the abundance of general bacteria and more specifically, those belonging to the genus Vibrio were reduced within temperate Zostera marina (eelgrass) meadows compared to adjacent sand flats and sampled 5 sites in the south-western Baltic Sea using SCUBA. Compared to non-vegetated area, we found an average reduction of 39% for all Vibrio and 63% for the potentially harmful V. vulnificus/cholerae subtype based on robust plate counting data on Vibrio selective agar. The underlying mechanism of the reduction in bacterial load is currently elusive and clearly merits further study. Our results underline the critical importance of seagrasses in maintaining shallow water ecosystem functioning including water quality and provide further motivation for their protection and restoration.

Clathrina aurea was considered endemic to Brazil before being recorded from the Pacific (Peru) and the Caribbean Sea. We assessed the morphological variability, phylogeographic pattern and population genetic structure of the species across its geographic range to understand how habitat fragmentation/reduction can affect a widely distributed species with supposedly low dispersal capability. Samples from 15 localities in the Caribbean Sea (n = 8), Brazil (n = 5), and Peru (n = 2) were studied. Morphological analyses included characterisation of external morphology, skeleton composition, and spicules morphometry. Phylogenetic trees and haplotype network were constructed using rDNA sequences. Population structure was assessed using microsatellite loci (FST fixation index and Discriminant Analysis of Principal Components). Morphological traits were consistent with C. aurea, although certain differences have been found, possibly due to environmental factors (temperature and pH). Phylogenetic analyses corroborated the conspecificity of the individuals and indicated higher genetic variability in individuals from Brazil and Caribbean, compared to Peru. Phylogeographic analyses indicated that Brazil had the oldest population of C. aurea, suggesting the expansion of this species across the Amazon River to the Caribbean and its connectivity through intermediate populations (e.g., Abrolhos). Population structure analyses also revealed high levels of genetic connectivity between the Caribbean and Northeast Brazil and among Southeast Brazilian localities. All analyses indicated isolation or restricted gene flow between Pacific and Atlantic populations. This, combined with the reduced genetic diversity in Peru and the supposedly limited larval dispersal capability, suggest a possible non-natural dispersion; however, we cannot exclude other hypotheses.

For intertidal marine species, salinity and temperature are important environmental factors with conditions ranging from oceanic salinity and temperature at high tide to almost freshwater conditions due to rain accompanied by aerial temperature exposure at low tide. The interactive effects of these stressors across development to the juvenile is not known. We investigated the impacts of salinity (29–41 ppt) and temperature (20°–24 ℃) on holobenthic intertidal development to the five-armed juvenile asterinid seastar Parvulastra exigua. There was an interaction between the stressors with highest mortality in the high salinity and temperature (38 ppt, 41 ppt, 24 ℃) treatments. Developmental stage progression was enhanced by increased temperature. On day 1, there was an interaction between salinity and temperature on developmental stage progression, where high salinity (41 ppt) retarded development at the control temperature (20 ℃). The juveniles reared at 24 ℃ were smaller than those at cooler temperatures, suggesting application of the temperature size rule. The low (29 ppt) and high (38 ppt, 41 ppt) salinity treatments produced the smallest and largest juveniles, respectively. In the 35 ppt and 38 ppt salinity conditions at 20 ℃, most juveniles had the normal five-armed profile. Body plan development was perturbed with deviations from pentamery at 29 ppt, 32 ppt and 41 ppt and at 22 ℃ and 24 ℃ in formation of no armed juveniles and ones with abnormal arm number (4, 6, 7 arms). Normal development at 35–38 ppt and 20–22 ℃ reflects breeding period conditions. Prolonged exposure to low and high salinity and increased temperature is deleterious to development in P. exigua and alters body morphology with implications for function and survival.

Ocean warming is affecting marine ectothermic herbivores as well as the macroalgal species they consume and this has the potential to alter their trophic interaction. However, it is currently still unknown how these two important components of benthic food webs will react to a warming environment. Consumption rates of grazers change with increasing temperatures, but it is unclear whether this is also true for feeding preferences. In this study, multiple-choice feeding assays with the tropical abalone Haliotis squamata from Western Indonesia were conducted in August 2018. After brief acclimation of either the grazer or the macroalgae to moderately elevated water temperatures (maximum 2 °C above the long-term average) in the laboratory, three species of living macroalgae were simultaneously offered to the abalone in feeding assays. Consumption rates of H. squamata were lower under elevated water temperatures, while its feeding preference switched: At 27 °C (2 °C below long-term average), abalone preferred non-acclimated Gracilaria salicornia, but switched to non-acclimated Amphiroa spp. at 31 °C. Interestingly, no such switch in preference occurred when the macroalgae, but not the grazers were acclimated. This indicates that the grazer will presumably be the driver of this potential change in interactions between H. squamata and its macroalgal food. Ocean warming may result in changes in the structure of benthic communities, mediated by changes in the feeding behaviour of herbivorous invertebrates.

Climate change is transforming coral reef structures, with important yet largely unknown consequences for reef food webs. Crustaceans, molluscs, polychaetes, and other small motile invertebrates living as epifauna on coral habitats represent an essential trophic link between primary producers and a diverse and abundant invertivorous fish fauna. Here, we investigate variation in assemblages of motile epifaunal invertebrates on live coral and dead coral heavily overgrown by turf algae. Sampling was conducted 2–3 years following mass bleaching within the study region at four locations broadly spanning the distribution of corals on the eastern seaboard of Australia—along the northern and central Great Barrier Reef, and, adjacent to the central east coast, the Solitary Islands and offshore Elizabeth and Middleton Reefs (> 2000 km total distance). Epifaunal assemblages differed significantly between live and dead ‘turf-covered’ coral habitats, with overall density, biomass, and productivity of epifauna more than an order of magnitude greater on dead than on live coral. The size structure and composition of assemblages also differed: turf-covered dead coral supported greater abundances of small animals than live coral, notably harpacticoid copepods, while live coral assemblages had proportionally greater abundances of larger decapods. A ten-fold increase in secondary productivity of motile invertebrates is predicted as live corals are replaced by turf-covered dead coral, however, this productivity will predominantly be available as small harpacticoid copepod prey (size range: 0.125–0.25 mm). Associated flow-on effects through reef food webs are likely, as changes to epifauna will directly affect invertivore communities, which in turn potentially influence larger carnivores and other functional groups.

Characterization of species diversity of zooplankton is key to understanding, assessing, and predicting the function and future of pelagic ecosystems throughout the global ocean. The marine zooplankton assemblage, including only metazoans, is highly diverse and taxonomically complex, with an estimated ~28,000 species of 41 major taxonomic groups. This review provides a comprehensive summary of DNA sequences for the barcode region of mitochondrial cytochrome oxidase I (COI) for identified specimens. The foundation of this summary is the MetaZooGene Barcode Atlas and Database (MZGdb), a new open-access data and metadata portal that is linked to NCBI GenBank and BOLD data repositories. The MZGdb provides enhanced quality control and tools for assembling COI reference sequence databases that are specific to selected taxonomic groups and/or ocean regions, with associated metadata (e.g., collection georeferencing, verification of species identification, molecular protocols), and tools for statistical analysis, mapping, and visualization. To date, over 150,000 COI sequences for ~ 5600 described species of marine metazoan plankton (including holo- and meroplankton) are available via the MZGdb portal. This review uses the MZGdb as a resource for summaries of COI barcode data and metadata for important taxonomic groups of marine zooplankton and selected regions, including the North Atlantic, Arctic, North Pacific, and Southern Oceans. The MZGdb is designed to provide a foundation for analysis of species diversity of marine zooplankton based on DNA barcoding and metabarcoding for assessment of marine ecosystems and rapid detection of the impacts of climate change.

The responses of ectothermic organisms to changes in temperature can be modified by acclimatization or adaptation to local thermal conditions. Thus, the effect of global warming and the deleterious effects of extreme heating events (e.g., heatwaves) on the metabolism and fitness of ectotherms can be population specific and reduced at warmer sites. We tested the hypothesis that when environmental temperature is greater, grazer populations in the Galapagos are less thermally sensitive (potentially due to acclimatization or adaptation). We quantified the acute thermal sensitivity of four populations of the pencil sea urchin, Eucidaris galapagensis, by measuring individual oxygen consumption across a range of temperatures. Thermal performance curves were estimated for each population and compared to local thermal conditions 2 months prior to collection. Results indicate that E. galapagensis populations were adapted and/or acclimatized to short-term local temperature as populations at warmer sites had substantially higher thermal tolerances. The acute thermal optimum (Topt) for the warmest and coolest site populations differed by 3 °C and the Topt was positively correlated with maximum temperature recorded at each site. Additionally, temperature-normalized respiration rate and activation energy (E) were negatively related to the maximum temperature. Understanding the temperature-dependent performance of the pencil urchin (the most significant mesograzer in this system), including its population specificity, provides insight into how herbivores and the functions they perform might be affected by further ocean heating.

International audience; Seabirds are one of the most threatened of all bird groups, with a marked community-wide decline across the last decades. Yet, some seabird species are more resilient than others, and it is essential to study under which conditions even these highly resilient organisms are affected by global changes. Using global location sensors (GLS), demographic and stable isotope analyses, we performed a long-term study of the migration biology and inter-annual survival of northern gannets (Morus bassanus) breeding on Rouzic Island in Brittany, France. Across 2006-2015, our analyses showed that the birds spent the inter-breeding period off Western Europe, in the Mediterranean or off West Africa. There were no inter-annual trends in the use of these different areas, but isotopic analyses suggested food competition between gannets and industrial-scale fisheries. Crucially, we found a precipitous decline in the return rates of birds equipped with GLS, from 90% in 2006-2007 to less than 10% after 2015. This decline was consistent with a marked decrease in inter-annual survival probabilities for ringed adult gannets, from >90% in 2014-2015 to

Copepods are an important link in marine food webs, transferring crucial nutrients such as essential fatty acids (EFA) from primary producers to higher consumers. Yet data on lipid dynamics in marine ecosystems associated with small lipid-poor copepods are scarce. In this study, we used the coastal calanoid copepod Eurytemora herdmani, which is an opportunistic generalist feeder, to assess EFA-specific gross growth efficiency (GGEEFA), defined as the fraction of ingested EFA retained in copepod tissue. We conducted two eight-day feeding experiments with 13C-labeled phytoplankton to quantify incorporation and GGEEFA of eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) in stage CV E. herdmani copepodites consuming either the EPA-replete diatom Thalassiosira weissflogii or the DHA-replete mixotrophic dinoflagellate Heterocapsa triquetra. EFA incorporation was quantified using gas chromatography. We recorded rapid shifts (within 48 h) in copepod tissue fatty acid (FA) composition following diet change, but not directly mirroring dietary algal FA. We also found high GGEEFA, with maxima of 46% and 61% for EPA and DHA, respectively, in copepods ingesting T. weissflogii and 39% and 87%, respectively, in copepods ingesting H. triquetra. GGEDHA remained higher than GGEEPA throughout the experiments regardless of dietary algae. GGEEFA decreased overall when copepods matured and produced nauplii, indicating EFA allocation for reproductive purposes. GGEDHA values in non-reproducing E. herdmani copepodites were high, suggesting that under predicted shifts in copepod community size structure, trophic transfer by small copepods could help compensate for DHA reductions resulting from lower abundances of large, lipid-rich species.

Habitat area and fragmentation are recognised as important factors that influence population size, community structure and extinction risk. Abundance and species richness universally increase with habitat area. However, the effects of different aspects of habitat fragmentation, including variation in patch size, number and isolation are often not distinguished from each other or the overall effects of habitat amount. Here we experimentally tested predictions concerning the effects of isolation on abundance, species richness and community structure of coral reef fishes colonising patch reefs by constructing clusters of patches of the same number and size, but manipulating reef spacing. Hexagonal clusters of 7 experimental patch reefs (6 edge and 1 central) with 3 levels of isolation (1 m, 5 m, and 15 m spacing) were established at Kavieng, Papua New Guinea and colonisation was recorded after 6 weeks in 2014. We also deployed video cameras to test whether isolation affected the activity of transient predatory fishes. As predicted, isolation had a positive effect on both mean abundance and species richness at both the cluster and patch scale. The cumulative abundance and species richness exhibited linear increases in relation to habitat area within clusters (from 1 to 7 patch reefs), but the slope increased with the degree of isolation. There was some evidence that transient predators remained longer and were more successful when patches were close together, which may explain the lower abundance and richness of juvenile fish assemblages on more aggregated patch reefs. This study demonstrates that while habitat amount is fundamentally important, isolation has significant effects that will need to be distinguished from other aspects of fragmentation when examining the processes structuring reef fish communities.

WOS:000569774900003; Over the past decades, several studies have revealed that the traditional view of the Antarctic Circumpolar Current (ACC) as an agent for species dispersal in the Southern Ocean is not applicable to all taxa. Some species are actually circum-Antarctically or circum-sub-Antarctically distributed, but some other species actually comprise species' complexes, with cryptic taxa occurring at different areas. However, to date, few of the invertebrate species formerly reported as widespread in the Southern Ocean have been re-analyzed using genetic techniques. This study examined whether two geographically distant areas of the sub-Antarctic region under the influence of the ACC, the Southern tip of South America (SSA) and the Prince Edward Islands (PEI), share some marine invertebrate species. For that, members of two genera of bivalves, Gaimardia and Hiatella, were selected. As part of this study, we found extremely low genetic differentiation between specimens from SSA and PEI. In addition, shared haplotypes were found between these two areas. Our results confirm that Gaimardia trapesina and one same species of Hiatella ("Hiatella O") are present in both areas. Given that these two species are found on macroalgae, natural rafts appear as the most plausible means of dispersal of juveniles and adults, although in the case of Hiatella O, additional larval dispersion cannot be discarded. In any of these cases, dispersion should be facilitated (or even determined) by the ACC. Thus, this study provides new evidence in favour of considering the ACC as an effective dispersive agent in the Southern Ocean.

The sea surface microlayer (SML) is the boundary layer between the ocean and the atmosphere and plays a unique role in marine biogeochemistry. Phytoplankton communities in this uppermost surface layer are exposed to extreme ultraviolet (UV) radiation and potentially high nutrient supplies. In order to understand the response of SML communities to such contrasting conditions, we conducted experiments at three different sites, the North Sea (open ocean) and two sites, outer and middle fjord, in the Sognefjord, Norway, with differing physical and chemical parameters. We manipulated light, nitrogen (N) and phosphorus (P) supply to natural communities collected from the SML and compared their response to that of the underlying water (ULW) communities at 1-m depth. Phytoplankton communities in both SML and ULW responded significantly to N addition, suggesting the upper 1-m surface phytoplankton communities were N-limited. While phytoplankton growth rates were higher with high N and high light supply, biomass yield was higher under low light conditions and with a combined N and P supply. Furthermore, biomass yield was generally higher in the ULW communities compared to SML communities. Nutrient and light effects on phytoplankton growth rates, particulate organic carbon (POC) and stoichiometry varied with geographical location. Phytoplankton growth rates in both SML and ULW at the open ocean station, the site with highest salinity, did not respond to light changes, whereas the communities in the middle fjord, characterized by high turbidity and low salinity, did experience light limitation. This work on the upper surface phytoplankton communities provides new insights into possible effects of coastal darkening and increases understanding of oceanic biogeochemical cycling.

The recovery of populations and their ability to recolonise a disturbed habitat is mainly dependent on their reproductive biology (e.g., fecundity, frequency of reproduction, and time to maturity) and recruitment success. To assess recolonisation processes and connectivity of vent communities, and infer their resilience to natural and anthropogenic disturbances, we studied the life-history traits of two dominant species of vent gastropods from the northern Mid-Atlantic Ridge: Protolira valvatoides and Pseudorimula midatlantica. Gonad morphology, gametogenesis, and reproductive outputs related to shell length were described using histological analyses, and population structure was assessed from individuals’ size–frequency distributions. Samples were collected at different locations of the Montségur and Eiffel Tower edifices (Lucky Strike vent field) in April 2015, July 2017, and August 2018 to inform on spatial and temporal variations of their reproductive outputs and demography. All stages of oocyte development were found in the gonads of both species, suggesting a continuous gametogenesis and asynchronous reproduction. However, the two species showed contrasting reproductive strategies. Indeed, while P. midatlantica is gonochoric with a fecundity of up to 327 mature oocytes, P. valvatoides is hermaphrodite with an extremely low fecundity including a maximum of eight vitellogenic oocytes. Maximum oocyte size was 176 µm for P. midatlantica and 272 µm for P. valvatoides. We infer from previous knowledge and our results that both species exhibit a lecithotrophic development of larvae. There was no evidence of temporal variability of reproductive traits, but environmental conditions seem to affect gametogenetic maturity and oocyte size of P. midatlantica limpets. Variations in population structure at the edifice scale suggest habitat selection of individuals related to biotic and abiotic factors.

Aquatic ecosystems face a multitude of environmental stressors, including warming and acidification. While warming is expected to have a pronounced effect on plankton communities, many components of the plankton seem fairly robust towards realistic end-of-century acidification conditions. However, interactions of the two stressors and the inclusion of further factors such as nutrient concentration and trophic interactions are expected to change this outcome. We investigated the effects of warming and high CO2 on a nutrient-deplete late summer plankton community from the Kiel Fjord, Baltic Sea, using a mesocosm setup crossing two temperatures with a gradient of CO2. Phytoplankton and microzooplankton (MZP) growth rates as well as biomass, taxonomic composition, and grazing rates of MZP were analysed. We observed effects of high CO2, warming, and their interactions on all measured parameters. The occurrence and direction of the effects were dependent on the phytoplankton or MZP community composition. In addition, the abundance of small-sized phytoplankton was identified as one of the most important factors in shaping the MZP community composition. Overall, our results indicate that an estuarine MZP community used to strong natural fluctuations in CO2 can still be affected by a moderate increase in CO2 if it occurs in combination with warming and during a nutrient-deplete post-bloom situation. This highlights the importance of including trophic interactions and seasonality aspects when assessing climate change effects on marine zooplankton communities.

Trans-generational plasticity (TGP) represents a primary mechanism for guaranteeing species persistence under rapid global changes. To date, no study on TGP responses of marine organisms to global change scenarios in the ocean has been conducted on phylogenetically closely related species, and we thus lack a true appreciation for TGP inter-species variation. Consequently, we examined the tolerance and TGP of life-history and physiological traits in two annelid species within the genus Ophryotrocha: one rare (O. robusta) and one common (O. japonica). Both species were exposed over two generations to ocean acidification (OA) and warming (OW) in isolation and in combination (OAW). Warming scenarios led to a decrease in energy production together with an increase in energy requirements, which was lethal for O. robusta before viable offspring could be produced by the F1. Under OA conditions, O. robusta was able to reach the second generation, despite showing lower survival and reproductive performance when compared to control conditions. This was accompanied by a marked increase in fecundity and egg volume in F2 females, suggesting high capacity for TGP under OA. In contrast, O. japonica thrived under all scenarios across both generations, maintaining its fitness levels via adjusting its metabolomic profile. Overall, the two species investigated show a great deal of difference in their ability to tolerate and respond via TGP to future global changes. We emphasize the potential implications this can have for the determination of extinction risk, and consequently, the conservation of phylogenetically closely related species.

To use seabirds as ecological sentinels of marine ecosystems under the incidence of global changes, it is essential to understand linkages between their spatial ecology and environmental conditions. Such information is still lacking for some key areas, including in Europe. We studied the spatial ecology of European shags (Phalacrocorax aristotelis) in Normandy, France, where > 1% of the species’ world population, and ca. 20% of its French population breeds. Working on 29 breeding individuals at two colonies (Chausey and Saint-Marcouf), we performed the first GPS-tracking study for the species in this region. On the basis of GPS positions and dive information across 244 foraging trips, we present a general methodological framework to map existing, and model potential seabird habitats. Shags performed dives between 9 and 17 h, and fed at average distances of 5.3 km (Chausey) and 3.3 km (Saint-Marcouf) from their nests. They used 186 km2 (Chausey) and 143 km2 (Saint-Marcouf) areas with a depth

Knowledge of the relationship between auditory form and function is necessary to understand the role of hearing in fish ecology, as well as the potential impacts of anthropogenic noise and environmental change on hearing-mediated functions. We explored the functional significance of otolith (ear stone) morphology in a large predatory sciaenid, Argyrosomus japonicus (Temminck and Schlegel), by comparing ontogenetic changes in otolith structure to changes in habitat, diet and swimming activity. We examined an otolith metric that has previously been linked to habitat use and activity in fishes, the relative sensory area (sulcus to otolith area ratio, S:O), and a new metric that quantifies the protuberant structure (calcareous concrescence) found on the distal surface of sciaenid otoliths (otolith perimeter to area ratio, P:SA). Strong allometric growth of the sulcus acusticus was detected in the sagitta of A. japonicus ranging from 7 to 80 cm TL. Both S:O and P:SA changed rapidly until A. japonicus reached 50 cm TL, after which only a gradual increase in relative sensory area was detected. The aspect ratio of the caudal fin (CAR, an index of swimming activity) abruptly increased in A. japonicus at 41–50 cm TL. These changes coincide with an observed shift in diet from benthic invertebrates to pelagic fish, a shift in foraging habitat and an increase in foraging activity.

Ecological impacts of top-down trophic cascades in combination with bottom-up nutrient enrichment are increasingly being reported. Such effects may be triggered by decline in the abundance and size of piscivore fish leading to a release of smaller-sized mesopredatory fish that are capable of reducing mesograzers and their buffering herbivorous effects, thus intensifying eutrophication symptoms. Hitherto, such mesopredator release has not been studied in controlled manner in macroalgal-dominated rocky shore communities. This study utilised twelve littoral mesocosms in southeastern Norway to investigate the impact of increased nutrient levels and increased abundance of the mesopredatory goldsinny wrasse (Ctenolabrus rupestris) over 6 months, from spring (April) to autumn (October). The study mainly revealed typical eutrophication responses in both July and in October with nutrient enrichment leading to more ephemeral algae and less perennial Fucacean and red macroalgae. Significant responses to the addition of mesopredatory fish alone or with nutrients in combination were clearly fewer in July and almost non-existent in October. Mesopredatory fish reduced the number of some mesograzers, but not others, and some herbivores even benefitted. Few joint effects occurred between fish and nutrients and the anticipated negative consequences for perennial macrophytes were largely absent; the possible reasons for these observations are discussed in depth. Curiously, the presence of mesopredatory fish seems to favour some canopy-forming macrophytes. This last finding warrants further investigation as the labrid fishery in coastal waters of southern Norway and western Sweden is increasing and a too heavy reduction of mesopredators may have its own unforeseen ecosystem implications.

Clonal behavior has been hypothesized to provide an escape from allometric metabolic scaling that limits the maximum mass achieved by a single individual. Here, we demonstrate the capacity of a wide-spread, non-native sea anemone to buffer its colony biomass accumulation rate across environments by modulating ramet body size through environmentally dependent growth, fission, and catabolism. In 2015, thermal reaction norms for growth and fission behavior were constructed using clonal lines of the sea anemone Diadumene lineata. In 2018, variation in growth patterns under a factorial cross of temperature level and oxygen availability was examined to test the hypothesis that individual ramet size is regulated by oxygen limitation in accordance with optimal size theory. Across a wide range of temperatures, colonies accumulated a similar amount of biomass despite a radical shift from unitary to clonal growth, supporting fission as a mechanism to buffer growth rates over a range of conditions. Individual body size appears to be regulated by the environment with increased temperature and reduced oxygen modifying fission and mass-specific growth patterns, leading to the production of smaller-bodied ramets in warm conditions. However, whether anemones in common garden conditions reduce individual body size through catabolism or fission depends on the region of origin and may relate to differences in seasonal temperature patterns among coastlines, which influence the energetic benefits of fission rate plasticity.

International audience; Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15N and 13C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis), and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the (1) ingested material and (2) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.

For all fishes, hatching is a short but crucial event, and the conditions under which it occurs considerably influence the success of the larvae. For coral reef fish, hatching is even more important because it marks the beginning of the dispersal phase. The timing of hatching dictates the conditions that the larvae will encounter, potentially influencing their survival and dispersal. Despite this importance, very few studies have looked at hatching of marine fishes in the natural environment because of important technical constrains. In this study, we directly examined the temporal pattern of hatching during the night. Using remote night vision cameras and infrared lights to avoid disturbances, we successfully documented in situ hatching events of three coral reef fish species, all benthic brooders (Abudefduf saxatilis, Stegastes partitus, and Elacatinus lori). Hatching timing, rate, and duration were computed from the observations, and highlight different hatching strategies used by the fish species. The analysis of the fish behaviors shows that the males display parental care beyond the incubation period of the eggs and increase activity during the hatching events. With this study, we can relate the hatching events to the environmental context, giving us a better understanding of the factors influencing the beginning of the larval phase. These observations highlight the benefit of in situ studies to better understand the characteristics and potential consequences of hatching.

Interspecific interactions help to shape individual- and population-level dynamics. As such, similar species breeding sympatrically are expected to have a high potential for competition and, thus, may have developed strategies to reduce niche overlap to allow coexistence. We combined GPS tracking and stable isotope analysis (δ15N, δ13C) to simultaneously compare multiple behavioral and dietary niche dimensions of common murres (Uria aalge) and razorbills (Alca torda) breeding at nearby colonies (55 km apart) on the northeastern Newfoundland coast under varying prey availability in 2017. Though foraging ranges of species had high potential overlap (5000 km2), foraging areas of the two species were spatially segregated. Dive characteristics also differed, as predicted based on body size and dive capacity. These differences contrasted a high degree of overlap in diet, habitat characteristics, and diurnal foraging patterns, suggesting that spatial segregation may be the most important factor to allow coexistence of these similar species for the same limited resources. As prey availability increased later in the breeding season, individual murres and razorbills foraged closer to their respective colonies and population-level diet composition changed, indicative of reduced energy costs and dietary plasticity to take advantage of highly available prey, capelin (Mallotus villosus). Foraging areas, however, remained segregated. Seabirds and marine systems face many potential threats, the greatest of which may be climate change. Thus, understanding variation in space, time, and habitat selection among similar species allowed for a more comprehensive view of the possible ways these species may partition their niche and how future changes to resource availability could impact interspecific relationships.

The accumulation of CO2 in the atmosphere and resulting ocean acidification represent a threat to marine ecosystems. While acid–base regulatory capacity is well developed in marine fish, allowing compensation of extra-cellular pH during short-term hypercapnia, the possible energetic costs of such regulation during long-term exposure remain to be established. In this study, juvenile European sea bass (Dicentrarchus labrax) were exposed from 2 days post-hatching to three different ocean acidification scenarios: control (present condition, $$ P_{{{\text{CO}}_{2} }} $$ = 520 µatm, pH 7.9), moderate acidification ( $$ P_{{{\text{CO}}_{2} }} $$ = 950 µatm, pH 7.7), and high acidification ( $$ P_{{{\text{CO}}_{2} }} $$ = 1490 µatm, pH 7.5). After 1.5 years of exposure, fish aerobic metabolic capacities, as well as elements of their oxygen extraction and transport chain, were measured. Compared to control, $$ P_{{{\text{CO}}_{2} }} $$ treatments did not affect fish standard metabolic rate (SMR). However, the most severe acidification condition was associated with a significantly elevated maximum metabolic rate (MMR).This was supported by heavier gill system and higher blood haemoglobin concentration. A reduction of maximum cardiac frequency (fHmax) during incremental warming of anaesthetized fish was also observed in both acidification scenarios. On the other hand, the critical oxygen level (O2crit), the minimum oxygen level required to sustain SMR, did not differ among groups. The increased MMR, associated with maintained SMR, suggests that acid–base compensatory processes, although not increasing maintenance costs, may affect components of bass homeostasis, resulting in new internal physico-chemical conditions. The possibility that these alterations influence metabolic pathways and physiological functions involved in fish aptitude to maximally transport oxygen is discussed.

The biochemistry of marine mammal blubber differs vertically from skin to muscle, which forms a challenge for using fatty acids (FAs) from differently sampled blubber as a proxy for dietary studies required for ecosystem-based management of coastal resources. In the blubber of some phocid seal individuals, the vertical stratification of several FAs is pronounced whereas in others the FAs distribute almost evenly through the blubber column. Using gas chromatography, we analysed the blubber vertical FA profiles of 30 adult male grey seals from the Baltic Sea, and examined which factors induced the largest vertical change of FA composition detected at the depth of 15–18 mm (outer and middle blubber boundaries). It was revealed that the degree of this compositional shift did not depend on the blubber thickness. Seal age only affected the vertical distribution of the FAs 16:0 and 16:1n-7. However, the outer blubber ratio of ∆9-desaturated monounsaturated FAs (MUFAs) to their saturated FA (SFA) precursors was not increased by grey seal age, contrasting earlier findings for ringed seals. A major determinant of the degree of FA stratification between the outer and middle blubber was the mismatch between the individually varying FA composition of the innermost blubber, regarded to reflect the dietary FA supply the most, and the uniform FA composition of endogenously regulated MUFA-rich outer blubber. Thus, discarding a fixed-depth layer of the grey seal outermost blubber, which we here show to span 0–18 mm from skin and which to a lesser extent reflects the diet of the individual, may in the case of small pinnipeds improve the sensitivity of the FA analysis in assessing spatial, temporal and individual dietary differences. When studying the outer blubber samples using only the diet-derived PUFA variables (SFAs and MUFAs omitted), the sensitivity of the analysis was better than when using this sample type with all main FA variables included. publishedVersion

A wide range of taxa have been shown to display inducible, phenotypically plastic responses to known predators. Most studies of inducible defenses include only known predators but not non-predatory species in experimental designs, precluding tests of specificity for these responses. We tested the specificity of predator-induced defenses in the marine snail Nucella lamellosa, when exposed to chemical cues from potential crab predators as well as more distantly related non-predatory crabs that co-occur with this snail. Surprisingly, all crabs tested, even those that are not predators, triggered the common induced response of a reduction of soft-tissue mass relative to control animals, likely reflecting a reduction in snail feeding activity. In contrast, only N. lamellosa’s major predator, Cancer productus, triggered the production of a thicker apertural lip. Increased thickening of the apertural lip may be an adaptive response specific to C. productus, which uses shell-breaking at the apertural lip (i.e., shell-peeling) as their main form of attack. Apertural lip thickening appeared to be due to reallocation of shell material (i.e., a change in shell shape) rather than an increase in shell deposition. Our findings demonstrate the importance of determining the specificity of cues triggering inducible responses in prey, and the mechanisms that underlie these plastic responses, as the responses to general versus specific cues may limit the adaptive value of an inducible defense.

The foraging ecology of breeding seabirds is largely influenced by prey availability and energy demands related to reproduction which, in combination with other factors, can affect resource specialization in space and time. In this study, we combined GPS tracking, dive behavior, and stable isotope ratios of carbon and nitrogen to examine behavioral and dietary flexibility within individuals in a breeding pursuit-diving seabird, the common murre (Uria aalge), on the northeast Newfoundland coast. We examined individual flexibility over 2 years (2016, 2017) during which the timing of arrival and availability of their primary prey, capelin (Mallotus villosus), varied. In both years, we found high within-individual variation in foraging trip and dive characteristics, coupled with low spatial overlap of foraging trips both within and among individuals, indicative of flexible behavior. Concurrently, the isotopic niche of breeding common murres showed a higher degree of dietary consistency, evidenced by similar amounts of variation within and among individuals in stable isotope ratios (δ13C, δ15N). Dietary reconstruction revealed that the proportion of different prey types in the diet varied across individuals, suggesting a degree of dietary flexibility. When capelin (prey) availability was low (in 2017), foraging trips were longer and farther from the colony, maximum dive duration decreased, and the proportion of capelin in the diet decreased. Behavioral flexibility, however, remained similar across both years, regardless of prey availability. Our results suggest that common murres can tolerate and respond to fluctuations in prey availability through flexible foraging strategies. Increased foraging distances during low capelin availability suggest increased energetic costs, and thus, an energetic threshold may be reached above which lower prey availability cannot be tolerated.

Kelp-derived detritus is a potential food item at the base level of marine food webs. A good knowledge of the factors that influence stable isotope composition in kelps is essential for reliable food web models. The variation of stable isotope signatures was analysed in three species of kelp in Kongsfjorden, Svalbard. Between 15 and 2.5 m depth, towards higher photon fluence rate, Alaria esculenta was gradually enriched in 13C while 15N did not change. The carbon/nitrogen ratio decreased with depth. 2- and 3-year-old kelp individuals had significantly higher δ15N values in their blades than 5- and 6-year-old ones. C/N ratio in blades remained statistically the same over the range of 2–6 years old plants. A two-way ANOVA did not show any interactive effects between depth and age group. A. esculenta as well as Saccharina latissima and Laminaria digitata exhibited enrichment in heavy carbon isotopes in the blades compared to the stipes, while within each species, δ15N values remained the same between blades and stipes. A more detailed analysis of kelp blades showed that independent of location in the fjord, year or season, and species, young tissue was more enriched in 13C than meristem and that decaying apical tissue was depleted relative to young tissue. The degree of this 13C depletion varied with kelp species. Meristem tissue appeared most uniform in the blades compared to young and decaying tissues and its δ13C signature was characteristic for each species with no significant difference in δ15N values. Decaying tissue showed no difference in δ13C between species. Carbon and nitrogen contents along the blades were species-specific and varied with growing location and year or season. Some advice is given on the temporal, spatial, and tissue-related choice of samples for different research objectives.

Sharks are a highly diverse predatory taxon and are regularly found in large, potentially competitive, assemblages. However, the mechanisms that enable long-term coexistence and factors that drive complementary movement are poorly understood. As interspecific interactions can have a large influence on survival and trophic linkages, research on shark assemblages could substantially increase our understanding of marine community dynamics. In this study, we used passive acoustic telemetry to compare the activity space size, spatial overlap and habitat use patterns of six co-occurring shark species from the same family in a tropical nearshore embayment. Our results indicated that all sizes of Rhizoprionodon taylori (a small-bodied, highly productive species) used significantly larger amounts of space (e.g., mean 95% KUD = 85.9 km2) than juveniles of large-bodied, less productive species (e.g., Carcharhinus amboinensis; 62.3 km2) that use nearshore areas as nursery areas. Most large, less productive species appeared risk averse by using less space, while the smaller more productive species took greater risk by roaming broadly. These movement strategies are likely a means of avoiding predation or gaining access to new or additional resources. Spatial overlap patterns varied substantially between species with overlap in core use areas ranging from 1.2 to 27.6%, but were consistent over time. Most species exhibited low spatial overlap, suggesting spatial partitioning to reduce interspecific competition. While a few species exhibited a high degree of spatial overlap (up to 60% of activity space extent), dietary diversity may reduce competition to support co-occurrence. These data suggest that complex interactions occur in communal nurseries in nearshore waters where species are in direct competition for resources at vulnerable life stages.

Biological invasions are often characterized by a phase of post-establishment expansion in which the invading species increases its range through colonization of new geographic areas. These expansions are predicted to result in specific genetic signatures, most notably decreased genetic diversity with distance from the point of introduction. The Asian caridean shrimp Palaemon macrodactylus is an introduced species in many regions of the globe. It has most recently invaded the U.S. Atlantic coast, with the first reported sighting in New York in 2001. This study used mitochondrial cytochrome oxidase I sequence data and data for 1598 single-nucleotide polymorphisms generated through restriction enzyme-associated DNA sequencing to evaluate two potential invasion mechanisms describing the spread of P. macrodactylus north of New York: the first based on a single introduction followed by range expansion facilitated by ocean currents, coastal transport, and physical environment; the second based on multiple introductions from overseas into different ports along the coast. We compare population genetic results to predictions of genetic patterns for each of these potential invasion pathways. Results do not support range expansion in which diversity decreases with distance from the point of first detection. Rather, the data suggest that multiple introductions may have taken place with population genomic diversity increasing with distance from New York, and peaks of mitochondrial diversity in populations collected from New York and the Boston–Plymouth coastline. These results indicate that multiple human-mediated dispersal events may be as important as oceanographic and life history considerations during the colonization phases of a marine invasion.

7 pages, 4 figures, 1 table, supplementary material https://doi.org/10.1007/s00227-019-3476-6, Dosidicus gigas (the Humboldt squid) is a widely distributed and ecologically important predator in the eastern Pacific Ocean, but its mating behaviour is poorly understood. Individuals of this species have undergone a drastic change in size at maturity in the last years. We investigated mating activity of Humboldt squid in the Gulf of California in 2013, 2014, and 2015 by quantifying spermatangia deposited in the tissue of the buccal area. In 2015, we encountered the smallest mean mantle length of mature specimens recorded to date in the Gulf of California. In all years, numerous males were encountered that had been mated by other males. Spermatangia in males were deposited on the tissue in similar numbers and in the same location as normally occurs in females (the buccal area), suggesting that male-to-male mating behaviour is similar to male-to-female. This behaviour is referred to as same-sex sexual behaviour and has been described for various taxa, including other cephalopods. Overall similarity in mating frequency between males and females and in body size of mated individuals (in 2015) suggests non-discriminative and brief encounters with body size being a cue for mating. This mating strategy may be beneficial for males, as Humboldt squid live in groups where competition for mates is likely high. The energetic costs of male-to-male mating events may be counterbalanced by the fitness profits of indiscriminate mating behaviour, HJTH was funded by a Grant (CP1218) of the Cluster of Excellence 80 “The Future Ocean.” “The Future Ocean” is funded within the framework of the Excellence Initiative by the Deutsche Forschungsgemeinschaft (DFG) on behalf of the German federal and state governments. FAFA was supported by Grants (BES-2013-063551 and EEBB-I- 15-09631) from the Spanish Ministry of Economy and Competitiveness (MINECO). WG acknowledges support from Stanford University and by Grants from the US National Science Foundation (IOS-1557754, OCE-1338973 RAPID, IOS-142093 EAGER, OCE 0850839), the National Geographic Committee for Research and Exploration (7578-04 and 9366-13), and Lindblad Expeditions-National Geographic Fund (LXII-15). EP was supported in part by the National Science Foundation Graduate Research Fellowship Program under Grant no. DGE-114747

The sensitivity of corals to ocean acidification depends on the extent to which they can buffer their calcifying fluid aragonite saturation state (Ωcf) from declines in seawater pH. While the seasonal response of the coral calcifying fluid Ωcf to seawater pH has been studied previously, relatively little is known about Ωcf dynamics on shorter (daily) timescales, particularly whether it is sensitive to seawater pH. Here, we use alizarin dye to mark 4 days of skeletal growth in the corals Acropora nasuta and Pocillopora damicornis living in situ on Ningaloo Reef in Western Australia. Exploiting newly developed confocal Raman spectroscopy techniques, we imaged the alizarin stains and quantified Ωcf between them. We report the first observations of diurnal Ωcf cycles, which were found in both species. Our results are consistent with either external control of Ωcf by seawater pH or light, or alternatively that Ωcf follows an endogenous circadian rhythm.

Some of the best-known disturbances affecting coral reefs are storms, yet their impacts on light are poorly known. Here, we describe the underwater light on a reef off St. John, US Virgin Islands (18°18′37.04N, 63°43′23.17W), during two hurricanes and multiple tropical waves that occurred between 17 August 2017 and 30 November 2017. Photosynthetically active radiation (PAR) was recorded at 19-m depth and at the surface, and rainfall was measured as a cause of turbidity affecting underwater light. Hurricanes Irma and Maria reduced maximum daily underwater photosynthetic photon flux density (PPFD) to

Intertidal and subtidal zones consist of heterogeneous habitats and dynamic environmental conditions, providing diverse options for fish to take advantage of marine resources. We explored how various environmental factors affected habitat use of an ecologically and economically important tropical marine fish, bonefish (Albula vulpes), on a fringing reef flat in Culebra, Puerto Rico, using a fine-scale acoustic telemetry positioning system. Machine learning algorithms and Bayesian inference via integrated nested Laplace approximation indicated diel period was the most important predictor of bonefish habitat use; bonefish occupied seagrass and mixed bottom (seagrass, macroalgae, sand) habitats most often at night, a deep-water soft sediment lagoon during the day, and infrequently used a shallow coral rubble reef crest. Zero-truncated (presence only) positioning frequency revealed more constrained utilization distributions during daytime and periods of higher water temperatures. Bonefish occupancy was highest in seagrass and mixed bottom habitats at lower water temperatures, and declined rapidly throughout the flat above 30 °C, which is consistent with temperature-mediated physiological constraints on performance (i.e. collapse of aerobic scope). Other factors including lunar phase, tidal state, and tide height had limited influence on bonefish habitat use. Building on a body of research, we propose several drivers of bonefish habitat use patterns amongst the diverse regions and habitats occupied, including predation risk, angling pressure, tidal variations, and temperature-related physiological performance. Our results emphasise the importance of conserving important seagrass foraging habitat through management and restoration.

International audience; Previous molecular studies have shown that many corals host a dynamic consortium of dominant and background populations of Symbiodiniaceae genotypes with putatively distinct physiological traits. In the present study, we developed a quantitative PCR assay combined with high-resolution melting analysis (qPCR–HRM) to distinguish which Symbiodiniaceae clades are present in a sample. Because the qPCR–HRM used in isolation yielded identical melt profiles for both clades A and C, this analysis was then coupled with further specific qPCR assays to enable the absolute quantification of all Symbiodiniaceae clades and host cells. When the assays were applied to in hospite samples, they had an absolute quantification level corresponding to one coral embryo of two cells and 1000 symbiont cells. The assays were successful on coral fragments from twelve species (eight families). We then used the qPCR–HRM assay in an ecological survey of Acropora pulchra at different spatial scales (within colony, between colonies and between sites). Differences in abundance and composition of Symbiodiniaceae clades in A. pulchra were observed at all spatial scales, suggesting that various environmental factors drove changes in Symbiodiniaceae assemblages among and within coral colonies. The qPCR–HRM assay developed in this study is a relatively simple, cost-effective and reproducible tool that can be used to accurately differentiate and quantify endosymbiont Symbiodiniaceae clades in coral in the field. This will provide new insights into coral-symbiont shuffling mechanisms and the resilience of coral colonies to environmental stressors.

Individual-based models are increasingly used by marine ecologists to predict species responses to environmental change on a mechanistic basis. Dynamic Energy Budget (DEB) models allow the simulation of physiological processes (maintenance, growth, reproduction) in response to variability in environmental drivers. High levels of computational capacity and remote-sensing technologies provide an opportunity to apply existing DEB models across global spatial scales. To do so, however, we must first test the assumption of stationarity, i.e., that parameter values estimated for populations in one location/time are valid for populations elsewhere. Using a validated DEB model parameterized for the cosmopolitan intertidal mussel Mytilus galloprovincialis, we ran growth simulations for native, Mediterranean Sea, populations and non-native, South African populations. The model performed well for native populations, but overestimated growth for non-native ones. Overestimations suggest that: (1) unaccounted variables may keep the physiological performance of non-native M. galloprovincialis in check, and/or (2) phenotypic plasticity or local adaptation could modulate responses under different environmental conditions. The study shows that stationary mechanistic models that aim to describe dynamics in complex physiological processes should be treated carefully when implemented across large spatial scales. Instead, we suggest placing the necessary effort into identifying the nuances that result in non-stationarity and explicitly accounting for them in geographic-scale mechanistic models.

Divergent foraging strategies may emerge within a population due to a combination of physiological and environmental factors; yet to persist, neither strategy should offer a consistent selective advantage over the alternative in the long term. Murphy’s petrels Pterodroma ultima from Henderson Island (24°20′S, 128°20′W) in the South Pacific Ocean are highly vagile, and exhibit two distinct foraging trip types during incubation; similar proportions of birds undertake either looping trips around the South Pacific Gyre to waters off Peru (hereafter “East”) or trips south-west of the colony towards the Subtropical Front (“South”) (mean maximum ranges of c. 3800 or 2000 km from the colony, respectively). However, the relative benefits of the distinct trip types remain unclear. Through tracking birds with GPS and salt-water immersion loggers in 2015, the fine-scale foraging behaviour was examined for East (trip durations: 14.1–19.8 days, maximum ranges 2387–4823 km) and South trips (12.9–25.8 days, 1565–1991 km). Data on behaviour classified from GPS tracks, the number of wet bouts per hour (a proxy for landing rates) and wind speeds, were used to distinguish two distinct foraging modes: birds on East trips spent more time in directed movement, whereas those on South trips spent a greater proportion of time in area-restricted search (ARS) behaviour. East trips were associated with higher overall mass gain, and wet bouts occurred in equal proportions during directed movement and ARS behaviour. This suggests that in unproductive marine environments, it may be more profitable to maximise area covered to increase the chances of encountering prey. Analysis of lower-resolution geolocator data (collected from 2011 to 2014) indicated that individuals were largely consistent in trip type between years. Since birds that conducted East trips were 19% lighter on departure from the colony and experienced more frequent tailwinds on foraging trips, we speculate that these birds may benefit from reduced movement costs, whilst also experiencing reduced competition for foraging opportunities. Electronic supplementary material The online version of this article (10.1007/s00227-018-3451-7) contains supplementary material, which is available to authorized users.

Coastal lobsters support important fsheries all over the world, but there is evidence that climate-induced changes may jeopardize some stocks. Here we present the frst global forecasts of changes in coastal lobster species distribution under climate change, using an ensemble of ecological niche models (ENMs). Global changes in richness were projected for 125 coastal lobster species for the end of the century, using a stabilization scenario (4.5 RCP). We compared projected changes in diversity with lobster fsheries data and found that losses in suitable habitat for coastal lobster species were mainly projected in areas with high commercial fshing interest, with species projected to contract their climatic envelope between 40 and 100%. Higher losses of spiny lobsters are projected in the coasts of wider Caribbean/Brazil, eastern Africa and Indo-Pacifc region, areas with several directed fsheries and aquacultures, while clawed lobsters are projected to shifts their envelope to northern latitudes likely afecting the North European, North American and Canadian fsheries. Fisheries represent an important resource for local and global economies and understanding how they might be afected by climate change scenarios is paramount when developing specifc or regional management strategies., The Portuguese Foundation for Science and Technology (FCT) supported this study through a PhD grant (SFRH/BD/51514/2011) to JBP and a Senior Research Position (FCT Development Grant 2013) to RR. MBA acknowledges the Integrated Program of IC&DT Call no. 1/SAESCTN/ALENT-07-0224-FEDER-001755 for support of his research.

Understanding the fine-scale movements and habitat use patterns of marine predators is critical for identifying important foraging habitat and guiding effective conservation planning. Here, GPS loggers were used to track chick-rearing Cassin’s auklets (Ptychoramphus aleuticus) at their largest breeding colony, located on Triangle Island, British Columbia, Canada (50°51′35″N; 129°4′34″W). Analyses were conducted at both the individual and population level to assess whether inter-annual variation in habitat use (2014, 2015, and 2017) could be explained by dynamic oceanographic features, such as sea surface temperature (SST) and chlorophyll a concentrations, or by static bathymetric features. At both scales of analyses, the foraging behaviour of Cassin’s auklets was most strongly influenced by SST. At the individual level, birds spent more time foraging in areas with lower SST, relative to other areas visited over the course of a foraging trip. At the population level, the at-sea distribution of Cassin’s auklets varied across years, with birds using areas northwest of colony in 2014 and areas west of the colony in 2015 and 2017. Furthermore, the probability of foraging across the study area was higher in areas with lower SST, suggesting that SST influences the broad-scale foraging distribution of Cassin’s auklets. Identification of the environmental drivers of habitat use across multiple years can be used to help in predicting suitable at-sea habitat across time, leading to more effective conservation management.

International audience; The combined impact of invasive species and climate change threatens natural systems worldwide, often facilitating the expansion of harmful invasive species. It is imperative to understand the mechanisms behind why species become invasive and widespread. Traditionally, it is thought that invasive species have greater tolerances to a wider array of environmental conditions than natives. We, therefore, tested the hypothesis that invasive species are more tolerant to the effects of short-term exposure to temperature and salinity stress. Using unifactorial experiments, we compared the tolerances of two common fouling NE Atlantic ascidians, the native Ciona intestinalis and the invasive Styela clava, to increased temperature and decreased salinity. We measured lethal and behavioural responses affecting 50% of populations to give an indication of the tolerance limits for temperature (LT50) and salinity (EC50), and respiration rate to give an indication of the change in metabolic response. The invasive S. clava was more tolerant to increased stress (LT50 = 29.5 °C, EC50 = 19.5) compared with C. intestinalis (LT50 = 27.0 °C, EC50 = 22.7), whereas both species displayed similar metabolic responses observed through increased respiration rates. This study is among the first to experimentally determine limits for temperature and hyposalinity stress for either species and supports the hypothesis that the invader performs better under extreme conditions. Future environmental changes caused by events such as heat waves and climate change could push species to the edge of their physiological limits, potentially facilitating competitive shifts between native and invasive species.

Thiamine (vitamin B1) deficiency in salmonids related to a lipid-rich fish diet causes offspring mortality in the yolk-sac fry phase. A low free thiamine (THIAM) concentration in eggs is an indication of this syndrome. Thiamine deficiency of salmon (Salmo salar) feeding in the Baltic Sea, called M74, was connected to the principal prey fish and feeding area using fatty acid (FA) signature analysis. The FAs of feeding salmon from two areas of the Baltic Sea, the Baltic Proper (57°10′ 19°30′) and the Bothnian Sea (61°30′ 20°00′) in 2004, reflected the principal prey species in these areas, sprat (Sprattus sprattus) and herring (Clupea harengus), respectively. Arachidonic acid (ARA, 20:4n-6) and 18:1n-7 indicated dietary herring, 18:1n-9 dietary sprat and 14:0 feeding in the Baltic Proper. The muscle FA profile of non-M74 female spawners of the River Simojoki in a year (1998) with a moderate M74 incidence and salmon of a non-M74 year (2004) reflected herring FAs, whereas the FAs in the M74 year and specifically in M74 females displayed characteristics of sprat. In the M74 year, the THIAM concentration had the strongest positive correlation with the proportion of muscle ARA, and the strongest negative correlations with 14:0 and the ratios 18:1n-9/ARA and 14:0/ARA. Thus, ARA along with 14:0 and these ratios were the most sensitive FA indicators of the dietary species and origin of the M74 syndrome. Despite the pre-spawning fasting, tissue FA signatures were consequently able to connect dietary sprat in the Baltic Proper with thiamine deficiency in Baltic salmon.

Studying genetic connectivity in marine populations aims to understand the dispersal of an organism through the seascape and thus its gene flow. Here, we focused on one lineage of the recently revised coral Pocillopora damicornis complex, P. damicornis type β, corresponding to Primary Species Hypothesis PSH05 in Gelin et al. (Mol Phylogenet Evol 109:430–446, 2017b): it had been hypothesized that P. damicornis type β encompasses four distinct lineages, representing Secondary Species Hypotheses (SSH05a, SSH05b, SSH05c and SSH05d). The aim of the present study was to confirm this partition and to infer the genetic structuring and connectivity among 27 populations for this widespread and common scleractinian. For this, a total of 1418 colonies were hierarchically sampled from two marine provinces of the southern parts of its distribution range, which remain largely understudied: the Western Indian Ocean and the Tropical Southwestern Pacific. Using 13 microsatellite loci and assignment tests, our findings confirmed the partition into four SSHs, each SSH splitting into clusters, suggesting that P. damicornis type β may represent a complex of cryptic species. Moreover, within each SSH, clonal propagation was evidenced in almost every population, but clonal dispersal was mostly restricted to sampling site (except in Reunion Island and northern Madagascar, where clones were found in several populations approximately 50 km apart). Nevertheless, wherever the cursor of species level is placed (one or several species), populations were highly differentiated both within the Western Indian Ocean and the Tropical Southwestern Pacific, suggesting restricted gene flow at different spatial scales (marine province, ecoregions, islands/regions), leading to diverging lineages.

Low recruitment due to limitations of propagule supply or post-settlement survival reinforces dominance of turf algal assemblages that replace canopy algae following large-scale losses. However, post-recruitment processes that hinder juvenile growth and survival (epiphytic overgrowth, grazing, physical stress) also could impede recovery. To evaluate the contribution of recruitment, growth, and survival of young sporophytes to recovery of degraded kelp populations and key factors driving post-recruitment tissue loss and mortality, we followed cohorts of juvenile kelp Saccharina latissima at two defoliated sites in Nova Scotia. We also monitored kelp recruitment, abundance, size structure, and macroalgal composition for 5.5 years. Recruit densities were an order of magnitude lower compared to previous studies in the region. Large decreases in blade area of juveniles were related to cover by the invasive bryozoan Membranipora membranacea, grazing by small snails Lacuna vincta, and warm seawater temperatures. Cohort survival was low (time to 50% mortality 2.5–5.5 months) and increased risk of death was directly related to bryozoan encrustation. Modest seasonal or interannual gains in kelp abundance were lost during periods of peak temperature, which showed a warming trend during the study, favouring persistence of widespread turf-forming, opportunistic and invasive algae. We conclude that low recruitment success, high rate of tissue loss relative to growth, and high mortality, inhibited kelp recovery. Impacts of epiphytic overgrowth, grazing, and warm temperatures on these processes highlight the need to protect intact kelp populations, growing in favourable conditions, to maintain positive interactions that increase resilience to undesirable regime shifts.

Baited cameras were deployed over a depth range of 532–5111 m in the Ionian Sea to characterise the large mobile fauna. The planned installation of a neutrino telescope also offers the potential for biological observatories. The current study was intended to aid observatory placement. At increasing depths, sediment was observed to become more uniform and animal burrows and tracks reduced. A total of 10 species of deep-sea fishes were identified from images; four elasmobranchs, which were not recorded deeper than 1841 m, and six teleosts. At depths > 3000 m, including Calypso Deep, the deepest point in the Mediterranean, only one fish species was observed; the Mediterranean grenadier, Coryphaenoides mediterraneus (3400–5111 m), extending this species’ maximum recorded depth to 5111 m. Four species of decapod crustacea could be identified from images. The dressed deep-sea shrimp, Acanthephyra eximia (1346–5111 m) was the only invertebrate recorded at abyssal depths, including the deepest point. A faunal change was detected at ~ 1000 m depth. Incorporating other studies from the Eastern Mediterranean identified additional faunal boundaries at ~ 1500 m and ~ 2500 m. The time from landing the observation equipment to the arrival of the first fish increased exponentially with depth at a slower rate to that observed in the Atlantic Ocean. The estimated density of bait-attending deep-sea fish was, therefore, significantly impoverished compared to the Atlantic Ocean at equivalent depth. Barriers to colonisation, low resource input, and high temperature at depth relative to the Atlantic Ocean are probable causes of the impoverished fauna. Electronic supplementary material The online version of this article (10.1007/s00227-018-3413-0) contains supplementary material, which is available to authorized users.

Many predictive models of spatial and temporal distribution (e.g. in response to climate change or species introductions) assume that species have one environmental niche that applies to all individuals. However, there is growing evidence that individuals can have environmental preferences that are narrower than the species niche. Such individual specialization has mainly been studied in terms of dietary niches, but a recent increase in the availability of individual movement data opens the possibility of extending these analyses to specialisation in environmental preferences. Yet, no study to date on individual specialisation has considered the environmental niche in its multidimensionality. Here we propose a new method for quantifying individual specialisation in multiple dimensions simultaneously. We compare the hypervolumes in n-dimensional environmental niche space of each individual against that of the population, testing for significant differences against a null model. The same method can be applied to a 2-dimensional geographic space to test for site fidelity. We applied this method to test for individual environmental specialisation (across three dimensions: sea surface temperature, eddy kinetic energy, depth) and for site fidelity among satellite-tracked black-browed albatrosses (Thalassarche melanophris) and grey-headed albatrosses (Thalassarche chrysostoma), during chick-rearing at South Georgia. We found evidence for site fidelity in both species and of environmental specialisation among individual grey-headed but not black-browed albatrosses. Specialisation can affect the resilience of populations affected by natural and anthropogenic changes in the environment, and hence has implications for population dynamics and conservation. Electronic supplementary material The online version of this article (10.1007/s00227-018-3408-x) contains supplementary material, which is available to authorized users.

Although hydrostatic pressure is one of the most prominent abiotic drivers of faunal bathymetric ranges, it is one of the least understood. To better understand hyperbaric constraints on depth distributions, we explored responses to high pressure of adult echinoderms from eastern Canada. The sea urchin Strongylocentrotus droebachiensis, the sea star Leptasterias polaris and the sea cucumber Cucumaria frondosa were exposed to various pressures within and beyond their known bathymetric distribution (i.e. surface pressure; pressure at the midpoint in bathymetric distribution; pressure at twice the maximum depth in the species bathymetric distribution) for different durations (24 h, 72 h, 9 days). Survival was compromised by exposure to the highest pressure levels, with the sea urchin exhibiting the highest mortality. After 72-h exposure, mortality was observed for sea urchin and sea cucumber individuals while all sea star individuals survived. Following 9-day exposure of sea star individuals to high pressure, 100% mortality occurred. Exposure to pressures typical of natural distributions had little effect on the selected health and motor metrics. Pressures atypical of natural ranges negatively affected the motor functions of all species, irrespective of exposure duration. During and after 24-h exposure, feeding was reduced in sea urchin and sea cucumber individuals, but was unchanged in sea star individuals. Overall, there were no clear signs of acclimation to high pressure following sustained periods of exposure in any species. These results highlight constraints applied by hydrostatic pressure beyond current bathymetric ranges on life-sustaining behaviours in echinoderms. The potential of long-lived echinoderms to survive downward migration to greater depths is species-specific, suggesting there may be winners and losers in the face of near-future climate-driven migration patterns.

Nearly all marine animals harbor epibionts, organisms living on their body surfaces. The positive or negative effects that epibionts have on their hosts depend on many factors, including the size and location of the epibionts on their host. The present study examined the effects of epibionts on gas exchange, locomotion, and drag of three species of Antarctic sea spiders (pycnogonids). Sea spiders are a cosmopolitan group of marine arthropods that lack gills and rely instead on the diffusion of oxygen directly across their cuticle. Encrusting epibionts, such as bryozoans and algae, had only minor effects on surface oxygen levels, but they reduced the functional diffusion coefficient of oxygen through the cuticle by about half. Although these effects are significant locally and may be severe in individuals with high coverage by epibionts, the total coverage on most individuals was not high enough to significantly alter oxygen fluxes into the animal. Macroepibionts, such as barnacles, had no effect on host walking speeds, but they increased by two-to-threefold the drag experienced by host sea spiders. This likely increases the energetic costs of walking and increases the chance of being dislodged by high currents. These results suggest that epibionts can impose diverse costs to their hosts but only in subtle ways that depend on total epibiont coverage of the host and rates of water flow.

Canopy-forming seaweeds are important foundation species or ecosystem engineers in intertidal habitats. By limiting a variety of abiotic stresses during low tides, algal canopies improve the performance of many understory organisms. The reduction of heat stress through substrate shading and moisture retention has received considerable attention in marine biology. However, the thermal influence of canopies during winter has not been empirically evaluated. Using intertidal fucoid canopies (Ascophyllum nodosum) from Atlantic Canada, we did a field experiment contrasting canopy-covered and no-canopy areas to test the hypothesis that canopies limit low temperatures during winter low tides. During 35 days between January and March, mid-intertidal temperature was often negative near the time of the lowest daily tides, on average more than 1 °C lower on bare substrate than under full canopy cover. The difference between both canopy treatments was higher around spring tides than around neap tides. Temperature on bare substrate was once even up to 10 °C lower than under a full canopy. Previous studies have shown that single occurrences of lethal negative temperatures and frequent occurrences of sublethal temperatures kill intertidal organisms every winter. Thus, our study suggests that, in addition to their bioprotective role during summer, canopy-forming seaweeds might also play a relevant facilitative role during winter.

As ocean temperatures continue to rise due to climate change, many questions remain on how coastal species will cope with a changing environment. The effects of increased temperatures on bivalves has been well examined through single-species studies, showing reductions in tissue mass, shell growth, oxygen uptake, feeding rates, and survival. However, the consequences of these effects on predator–prey interactions remain poorly understood. We examined how increased temperatures (30, 32, 34 °C) and the presence of water-borne predation cues from blue crabs (Callinectes sapidus) affected the morphology and growth rate of southern ribbed mussels (Geukensia granosissima), as well as their handling times when attacked by predatory crabs. Although southern ribbed mussels were able to survive under chronic heat stress, exposure to higher temperatures resulted in more elongated shell shapes. Growth rates in mussel wet weight were higher for mussels reared in the presence of a predator than in the predator-free control, but only in the low-temperature treatment. Likewise, handling times were greater for crabs eating mussels grown in the presence of a predator, but the effect was lost at the mid- and high-temperature treatments. These findings suggest that predation-induced defenses were suppressed when prey were under chronic thermal stress, which could make mussels more vulnerable to predation. The presence of predation cues in natural environments should be taken in consideration when estimating or predicting the effects of climate change on organisms.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Corals synthesise large quantities of the sulphur metabolite dimethylsulphoniopropionate (DMSP), which contributes to key roles in coral reef ecology including the capacity of corals to withstand various stressors. While closely related to scleractinian corals and often occupying similar ecological niche space, it is currently poorly defined to what extent soft corals produce DMSP. We, therefore, examined DMSP content within four key species of soft coral in February and July–August of 2017, including two temperate species from Sydney Harbour (Erythropodium hicksoni, Capnella gaboensis) and two tropical species from the Great Barrier Reef (Sinularia sp., Sarcophyton sp.). We compared DMSP content of these soft coral species to that of commonly occurring temperate (Plesiastrea versipora) and tropical (Acropora aspera) scleractinian coral species. DMSP content was normalised to coral protein content, with soft coral DMSP content highly variable across species and locations [56–539 nmol (mg protein)−1], and lower than for the tropical [1242–4710 nmol (mg protein)−1], but not temperate [465–1984 nmol (mg protein)−1] scleractinian species. Further comparison with previously published values demonstrated that soft coral DMSP content falls within the “low–mid range” of scleractinian corals. Notably, DMSP content was also higher in summer samples than winter samples for the scleractinian corals, but did not differ between seasons for soft corals. Such contrasting dynamics of DMSP production by soft corals compared to scleractinian corals indicates that the regulation of DMSP content differs between these two important benthic cnidarian groups, potentially as a consequence of dissimilar ecophysiological roles for this compound.