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For much of the pelagic sedimentary record, time control is limited to the resolution of precession cycles (ca 20 kyr): the Milankovitch parameter that forms the most detailed metronome for the Cenozoic and Mesozoic Eras. The influence of precession is often detected in lithological alternations, where the duration represented by individual lithologies is not well constrained. Here the novel technique of extraterrestrial helium abundance (3HeET) is used to investigate the sedimentation dynamics and palaeoceanography within individual precessional cycles. High‐resolution 3HeET timescales were produced for four precession cycles from the rhythmically bedded Scaglia Bianca Formation, a sequence of Upper Cretaceous (Cenomanian) deep‐marine pelagic limestones from central Italy that are well characterized by cyclostratigraphy. Using 3HeET concentrations as a proxy for sedimentation rate allows instantaneous sedimentation rates and organic‐carbon mass accumulation rates to be calculated for each bed within a precession cycle. Eccentricity is known to modulate the amplitude of precession forcing, and precession cycles deposited under eccentricity maxima and minima were selected for comparison. Lithological changes through these chert–(black shale)–limestone cycles are explained using the concept of 'palaeoenvironmental thresholds'; these timescale calculations indicate that when the amplitude of precessional insolation forcing was greatest (at eccentricity maxima) the palaeoenvironmental system spent longer in the more nutrient‐rich environment under which siliceous and organic‐rich sediments were deposited, reflecting increased time spent above a 'threshold' insolation level. Estimates of primary productivity are relatively elevated for organic‐rich beds. An increase in the flux of terrestrial helium (4Heterr) during the deposition of cherts may have been coincident with an increase in terrestrially derived nutrients. The presented results indicate great potential for the use of 3HeET to understand past oceanographic, climatic and sedimentological processes at high temporal resolution. [ABSTRACT FROM AUTHOR]

Microplastics’ presence in the pelagic environment is still largely unknown due to the difficulty of sampling in this part of the ocean. In this study, we quantify microplastics’ exposure in a pelagic lanternfish species from the western Mediterranean, Lampanyctus crocodilus (Risso 1810), which occupies an intermediate position in the marine food web. L. crocodilus were captured in the Ibiza Channel by a trawling vessel and microplastics were extracted by digestion of their gastrointestinal systems. Almost half of the analysed lanternfish contained microplastics, mostly blue and black fibres (40.9% and 34.66%, respectively). In fishes with at least one microplastic, the median was 3 MPs/fish (CI 95% = 3.46–6.8), similar to other studies performed in other fish species in the area. Biometric parameters of fish, such as total length and body condition, were not correlated with the number of microplastics. Data presented here contribute to quantifying the severity of microplastic pollution in the pelagic environment and in a wild, non-commercial species.

Microplastics' presence in the pelagic environment is still largely unknown due to the difficulty of sampling in this part of the ocean. In this study, we quantify microplastics' exposure in a pelagic lanternfish species from the western Mediterranean, Lampanyctus crocodilus (Risso 1810), which occupies an intermediate position in the marine food web. L. crocodilus were captured in the Ibiza Channel by a trawling vessel and microplastics were extracted by digestion of their gastrointestinal systems. Almost half of the analysed lanternfish contained microplastics, mostly blue and black fibres (40.9% and 34.66%, respectively). In fishes with at least one microplastic, the median was 3 MPs/fish (CI 95% = 3.46–6.8), similar to other studies performed in other fish species in the area. Biometric parameters of fish, such as total length and body condition, were not correlated with the number of microplastics. Data presented here contribute to quantifying the severity of microplastic pollution in the pelagic environment and in a wild, non-commercial species. [ABSTRACT FROM AUTHOR]

Simple Summary: This study reports the results of a multidisciplinary research on Mediterranean pelagic octopods belonging to the species Argonauta argo, Ocythoe tuberculata, Tremoctopus gracilis and Tremoctopus violaceus for the first time. The study area was the Strait of Messina and southern Tyrrhenian Sea. We used information from stranding events, accidental fishing catches and stomach contents of large predators (albacore, bluefin tuna, swordfish and Mediterranean spearfish). We analysed 47 fresh octopods, including exceptional records of rare males, and 330 individuals found in the stomachs of 800 predators. The analysis of genetic aspects was used to provide further details on the life and identity of these species. The present paper represents the first all-encompassing study on all Mediterranean holopelagic octopods belonging to Argonautoidea (Argonauta argo, Ocythoe tuberculata, Tremoctopus gracilis, Tremoctopus violaceus). Argonautoidea octopuses were collected by different sampling methods in the Strait of Messina and southern Tyrrhenian Sea. The aim of this paper was to improve knowledge, using information from different data sources, such as the study of stranded individuals or accidental caught specimens, as well as the analysis of stomach content of large pelagic fishes. Moreover, we investigated their taxonomic profile through the amplification of the mitochondrial cytochrome c oxidase subunit I (COI). Overall, 47 fresh holopelagic octopods were collected, including valuable records of rare males. Moreover, 330 Argonautoidea octopuses were found in the stomachs of 800 predators. The results provided evidence that these cephalopods are more abundant than thought in the past. The molecular approach supported the ecological results with interesting insights. The similarity-based identifications and tree-based methods indicated that three females could be identified as Tremoctopus violaceus in agreement with their morphological classifications. The sequences obtained from the two T. gracilis individuals were clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were differentiated from the sequences attributed to T. gracilis and T. robsoni. The study represents a valuable contribution to the genetic characterization of Mediterranean individuals of the genera Tremoctopus, Argonauta and Ocythoe. [ABSTRACT FROM AUTHOR]

Protist grazing pressure plays a major role in controlling aquatic bacterial populations, affecting energy flow through the microbial loop and biogeochemical cycles. Predator-escape mechanisms might play a crucial role in energy flow through the microbial loop, but are yet understudied. For example, some bacteria can use planktonic as well as surface-associated habitats, providing a potential escape mechanism to habitat-specific grazers. We investigated the escape response of the marine bacterium Marinobacter adhaerens in the presence of either planktonic (nanoflagellate: Cafeteria roenbergensis) or surface-associated (amoeba: Vannella anglica) protist predators, following population dynamics over time. In the presence of V. anglica, M. adhaerens cell density increased in the water, but decreased on solid surfaces, indicating an escape response towards the planktonic habitat. In contrast, the planktonic predator C. roenbergensis induced bacterial escape to the surface habitat. While C. roenbergensis cell numbers dropped substantially after a sharp initial increase, V. anglica exhibited a slow, but constant growth throughout the entire experiment. In the presence of C. roenbergensis, M. adhaerens rapidly formed cell clumps in the water habitat, which likely prevented consumption of the planktonic M. adhaerens by the flagellate, resulting in a strong decline in the predator population. Our results indicate an active escape of M. adhaerens via phenotypic plasticity (i.e., behavioral and morphological changes) against predator ingestion. This study highlights the potentially important role of behavioral escape mechanisms for community composition and energy flow in pelagic environments, especially with globally rising particle loads in aquatic systems through human activities and extreme weather events. [ABSTRACT FROM AUTHOR]

The present paper represents the first all-encompassing study on all Mediterranean holopelagic octopods belonging to Argonautoidea (Argonauta argo, Ocythoe tuberculata, Tremoctopus gracilis, Tremoctopus violaceus). Argonautoidea octopuses were collected by different sampling methods in the Strait of Messina and southern Tyrrhenian Sea. The aim of this paper was to improve knowledge, using information from different data sources, such as the study of stranded individuals or accidental caught specimens, as well as the analysis of stomach content of large pelagic fishes. Moreover, we investigated their taxonomic profile through the amplification of the mitochondrial cytochrome c oxidase subunit I (COI). Overall, 47 fresh holopelagic octopods were collected, including valuable records of rare males. Moreover, 330 Argonautoidea octopuses were found in the stomachs of 800 predators. The results provided evidence that these cephalopods are more abundant than thought in the past. The molecular approach supported the ecological results with interesting insights. The similarity-based identifications and tree-based methods indicated that three females could be identified as Tremoctopus violaceus in agreement with their morphological classifications. The sequences obtained from the two T. gracilis individuals were clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were differentiated from the sequences attributed to T. gracilis and T. robsoni. The study represents a valuable contribution to the genetic characterization of Mediterranean individuals of the genera Tremoctopus, Argonauta and Ocythoe.

The global ocean is commonly partitioned into 4 biomes subdivided into 56 biogeochemical provinces (BGCPs) following the accepted division proposed by Longhurst in 1998. Each province corresponds to a unique regional environment that shapes biodiversity and constrains ecosystem structure and functions. Biogeochemical provinces are dynamic entities that change their spatial extent and position with climate and are expected to be perturbated in the near future by global climate change. Here, we characterize the changes in spatial distribution of BGCPs from 1950 to 2100 using three earth system models under two representative concentration pathways (RCP 2.6 and 8.5). We project a reorganization of the current distribution of BGCPs driven mostly by a poleward shift in their distribution (18.4 km in average per decade). Projection of the future distribution of BGCPs also revealed the emergence of new climate that has no analog with past and current environmental conditions. These novel environmental conditions, here named No-Analog BGCPs State (NABS), will expand from 2040 to 2100 at a rate of 4.3 Mkm2 per decade (1.2% of the global ocean). We subsequently quantified the potential number of marine species and annual volume of fisheries catches that would experience such novel environmental conditions to roughly evaluate the impact of NABS on ecosystem services.

SUMMARY: Seafloor massive sulfide (SMS) deposits are the target of available metallic resources. The toxic impacts of leachable metals from hydrothermal ore by mining operations in marine environments are a concern. However, ecotoxicological knowledge about marine algae, and particularly open ocean species, is still limited. Here, we evaluated the toxic effects of three leachable metals (i.e. Zn, Cu, and Pb) on seven marine algae, including cyanobacteria and eukaryotes, by a delayed fluorescence method. Cyanobacterial Synechococcus and Cyanobium species were sensitive to Zn and Cu, while eukaryotic algae showed various responses to heavy metal species. The prasinophycean Bathycoccus prasinos NIES‐2670 was sensitive to all metal species; this strain is a potential test strain to detect the leachable metals. A co‐culture experiment showed that the impact on community structure varies depending on leachable metal species. This study demonstrates that surveys across multiple taxonomic groups are necessary to assess the impact of SMS‐mining operations on marine ecosystems as a whole. [ABSTRACT FROM AUTHOR]

This is the first record of the Pacific seahorse Hippocampus ingens at a northern oceanic island from the eastern Pacific Ocean. The photographic record of the juvenile female H. ingens was made in November 2015 during a cage diving trip at Guadalupe Island, Mexico. The presence of H. ingens in this area could be related to long distance dispersal mechanisms, as has been observed in other species of seahorses. [ABSTRACT FROM AUTHOR]

A recent increase in the construction of Offshore Wind Farms (OWFs) has initiated numerous environmental impact assessments and monitoring programs. These focus on sea mammals, seabirds, benthos or demersal fish, but generally ignore any potential effects OWFs may have on the pelagic ecosystem. The only work on the latter has been through modelling analyses, which predict localised impacts like enhanced vertical mixing leading to a decrease in seasonal stratification, as well as shelf-wide changes of tidal amplitudes. Here we provide for the first-time empirical bio-physical data from an OWF. The data were obtained by towing a remotely operated vehicle (TRIAXUS ROTV) through two non-operating OWFs in the summer stratified North Sea. The undulating TRIAXUS transects provided high-resolution CTD data accompanied by oxygen and chlorophyll- a measurements. We provide empirical indication that vertical mixing is increased within the OWFs, leading to a doming of the thermocline and a subsequent transport of nutrients into the surface mixed layer (SML). Nutrients were taken up rapidly because underwater photosynthetically active radiation (PAR) enabled net primary production in the entire water column, especially within submesoscale chlorophyll- a pillars that were observed at regular intervals within the OWF regions. Video Plankton Recorder (VPR) images revealed distinct meroplankton distribution patterns in a copepod-dominated plankton community. Hydroacoustic records did not show any OWF effects on the distribution of pelagic fish. The results of a pre-OWF survey show however, that it is difficult to fully separate the anthropogenic impacts from the natural variability. [ABSTRACT FROM AUTHOR]

We analyzed long-term dietary records of northern fur seals ( Callorhinus ursinus ) to reconstruct historical changes in prey availability and diversity in the western North Pacific off northeastern Japan. The nominal relationships between the occurrence frequencies of fishes or squids in fur seal stomachs and the sampling locations reflected the spatial heterogeneity of fish and squid distributions along the shelf–slope–offshore continuum off northeastern Japan, whereas changes in the temporal occurrence frequencies reflected mainly the migration and foraging patterns of the fur seals. The occurrence probabilities of fishes and squids in fur seal stomachs were standardized by using generalized linear models to compensate for sampling biases in space and time. The reconstructed historical trends revealed decadal shifts in relatively high prey abundance—from mackerels in the 1970s to Japanese sardine in the 1980s and myctophids/sparkling enope squids in the 1990s—that were related to decadal shifts in the oceanographic regime. The sequential increase in mackerel and Japanese sardine abundances coincided with the annual catch trends of commercial fisheries. The index of overall prey availability calculated from the standardized occurrence probabilities of fishes and squids in fur seal stomachs was fairly stable over the decades. [ABSTRACT FROM AUTHOR]

Understanding the community structure of oceanic higher trophic level (HTL) organisms (e.g., sharks, tunas, salmons, and squids) is fundamental to management of marine resources in a way that ensures their sustainable use and maintains marine ecosystem functionality and biodiversity. We analyzed the spatial structure of HTL assemblages in the western North Pacific Ocean using driftnet survey data collected at latitudes of 35–46 °N along transect lines at 144 °E, 155 °E, and 175.5 °E longitude in July and August 2011. We proposed a new dissimilarity metric segmentation procedure (Dissimilarity Segmentation) based on the differences of mean Bray-Curtis dissimilarity indices between two individual driftnet hauls within the same subarea or among different subareas. Dissimilarity Segmentation allowed us to divide the western North Pacific Ocean into three subareas: a northern subarea (>41 °N including 41 °N on the 175.5 °E transect), a transition subarea (37–41 °N), and a southern subarea (<37 °N). The HTL biomass in the northern subarea was high, and the species diversity was low; dominant and common species accounted for most of the biomass. The HTL assemblage in the southern subarea was composed of many species that were uncommon or rare; the biomass was lower, and the species diversity was higher than in the northern subarea. In the transition subarea, neon flying squid accounted for most of the biomass, and although the biomass was intermediate, species diversity was highest among the three subareas. Canonical correspondence analysis with oceanic environmental variables, principally chlorophyll a , sea surface salinity, and sea surface height, as the explanatory variables accounted for 43.6% of the variance of the HTL pelagic species composition. This result suggests that the HTL pelagic community in the western North Pacific is influenced largely by productivity and oceanic physical structure. These results suggest that an analytical approach based on Dissimilarity Segmentation combined with medium- to long-term survey datasets could facilitate the investigation of spatial-temporal variations in the spatial structure of HTL pelagic communities and the environmental causes thereof. [ABSTRACT FROM AUTHOR]

Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a ) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such as Alexandrium fundyense and A. ostenfeldii ) in the area points out the potential risk for this vulnerable ecosystem in a changing world. [ABSTRACT FROM AUTHOR]

Marine ecosystems have been significantly altered by the cumulative impacts of human activities. Pelagic sharks have become vulnerable to increases in mortality rates caused by fishing. The decrease in number of these top predators could have substantial cascading effects on wider marine communities. Concerns about these potential impacts, and the critical need for effective management, have led to an increased interest in assessing the trophic ecology of sharks. While stable isotope analyses have been used to provide relevant insights about the trophic ecology of sharks, the causal factors leading to trophic variation between individuals has been largely overlooked. Here, we investigated the relative effect of biological factors, geographic location, and environmental factors on the spatial trophodynamics of the blue shark (Prionace glauca). Specifically, stable isotope values of δ 15N and δ 13C, and the estimated trophic position (TP) were analysed for 180 blue sharks collected from south of the Canary Islands in the Atlantic Ocean, to the north-western Mediterranean Sea. The results showed that models which included combined variables explained the variation in δ 15N, TP and δ 13C values better than models which considered only stand-alone predictors. The independent contributions of environmental variables and biological factors seemed to be more important than geographic location for δ 15N and TP. δ 15N and TP increased in a curvilinear fashion with body size, and TP was higher for females. In the case of δ 13C values, only an effect from sex was observed. Among environmental variables, chlorophyll-a, pelagic productivity, and sea-surface temperature proved to be reliable predictors, particularly for δ 15N and TP, most likely due to their relationship with productivity and prey availability. This study provides new information on ranking the factors that influence the trophodynamics of the blue shark, namely the environment, the geographic location, and the biological factors of the species. • Ecological factors affect the trophodynamics of marine predators. • Blue sharks were sampled from Canary Island to the NW Mediterranean Sea. • The effect of biological and environmental factors on trophic markers was analysed. • Body size and sex partially explained stable isotope and trophic position values. • SST and marine productivity partially explained the trophic position. [ABSTRACT FROM AUTHOR]

This modeling study analyzes the simulated natural variability of pelagic ecosystems in the North Atlantic and North Pacific. Our model system includes a global Earth System Model (IPSL-CM5A-LR), the biogeochemical model PISCES and the ecosystem model APECOSM that simulates upper trophic level organisms using a size-based approach and three interactive pelagic communities (epipelagic, migratory and mesopelagic). Analyzing an idealized (e.g., no anthropogenic forcing) 300-yr long pre-industrial simulation, we find that low and high frequency variability is dominant for the large and small organisms, respectively. Our model shows that the size-range exhibiting the largest variability at a given frequency, defined as the resonant range, also depends on the community. At a given frequency, the resonant range of the epipelagic community includes larger organisms than that of the migratory community and similarly, the latter includes larger organisms than the resonant range of the mesopelagic community. This study shows that the simulated temporal variability of marine pelagic organisms' abundance is not only influenced by natural climate fluctuations but also by the structure of the pelagic community. As a consequence, the size- and community-dependent response of marine ecosystems to climate variability could impact the sustainability of fisheries in a warming world. [ABSTRACT FROM AUTHOR]

Sand lance or sand eels (Ammodytes spp.) are small planktivorous forage fishes that play an integral role in pelagic ecosystems in the Northern Hemisphere. Arctic sand lance (Ammodytes hexapterus) is prevalent in the North Pacific in the Sea of Okhotsk, northern Bering Sea, Chukchi Sea, and Beaufort Sea. Few studies have focused on this species despite its critical position in energy transfer and trophic food webs. Recent surveys in the Chukchi Sea and Beaufort Sea have noted an increase in the prevalence of this species in concert with reduced ice extent. Sand lance are unique among forage species in having close associations with specific water column conditions as well as a reliance on specific sand substrates for burrowing. Life history and habitat dependency is influenced by both dynamic oceanographic conditions and static benthic substrata. This taxa, therefore, provides a unique opportunity to examine the potential expansion of a boreal species into Arctic marine habitats. We use comprehensive surveys conducted throughout the Chukchi Sea shelf over multiple years to evaluate spatial distribution and abundance relative to oceanographic variables in the water column and sediment composition on the seafloor. We applied logistic regression and generalized additive models to investigate presence and relative abundance of Arctic sand lance and to evaluate spatial distribution, as a function of oceanographic and benthic environmental variables. Spatial distribution shifted considerably between years in response to environmental conditions. Arctic sand lance presence was influenced by surface water mass and positively associated with Alaskan Coastal Water. Relative abundance was positively associated with high surface temperature, low surface salinity, and coarser substrates. Evidence is mounting that the distributions of many boreal species are expanding on the margins of the Arctic. Our research reports increased aggregations of Arctic sand lance in the Chukchi Sea and at the highest latitude on record for this species, at the shelf break of the Arctic Basin. [ABSTRACT FROM AUTHOR]

Aim Rafting with natural flotsam is an important mechanism of long-distance oceanic dispersal for many near-shore marine organisms. Identifying the species- level traits associated with this behaviour would aid in understanding and predicting a species' capacity for dispersal between isolated areas of benthic habitat. Location The tropical and subtropical Atlantic. Methods We assessed the relationships between species-level traits (habitat use, position in water column, diet, body size, schooling activity) and rafting behaviour among 985 species of reef fish using generalized linear mixed-effect modelling. To assess whether the relationships between rafting behaviour and species traits were mediated by raft type, our analysis included interactions between raft type and our predictor variables. Results The following species-level traits are positively associated with rafting for reef fishes: (1) position in water column above reef substratum, which indicates a species' dependency on the substratum; (2) schooling behaviour, a trait linked to predation avoidance; (3) large adult size, which may be associated with enhanced survivorship and growth of rafting juveniles; and (4) broad habitat use, which may facilitate use of atypical habitats, including flotsam. Some correlations varied depending on the type of flotsam - broad habitat use is only positively correlated with the use of seaweed rafts, which may resemble patches of benthic macroalgal and seagrass beds that the reef fishes often use as ancillary habitat. In contrast, schooling behaviour is only positively correlated with rafting among logs and similar objects, perhaps because they represent poor refuges from predation. Main conclusions A species' propensity to use rafts is associated with specific ecological traits, some of which are contingent on characteristics of the raft. Thus, our findings suggest that increasing amounts of man-made flotsam entering the ocean may differentially influence future rafting opportunities among tropical reef fishes, depending on their traits, which may have important implications for their biogeographical distributions. [ABSTRACT FROM AUTHOR]

There are increasing demands for evaluation of the current status of marine ecosystems and impacts of environmental change and anthropogenic activities, but for the open ocean available data are quite limited. The Japanese driftnet survey dataset of Hokkaido University was used to analyze the spatio-temporal variations in the higher trophic level (HTL) community structure in the western North Pacific. The analyses were conducted by using subset of the data that was collected along four regularly surveyed transect lines at 155°E, 170°E, 175°E and 180°E spanning from 36 to 48°N and from 1982 to 1996. Non-size-selective multiple mesh driftnets were used in the survey. Total number of individuals, species richness and Simpson index of species diversity indicated a longitudinal gradient with a lower abundance and diversity in the eastern area. Latitudinal gradient was clear for numerical abundance and species richness, but no trend for Simpson diversity index. Temporal patterns in the HTL community structure were not consistent among the three metrics: numerical abundance showed a significantly decrease and increasing fluctuations in later years, species richness was increased along years, and Simpson index did not show any clear temporal trends. The inconsistency in the temporal patterns of community metrics was considered to arise from the effects of the sampling scheme on community measurements and/or complex structural changes such as the emergence of dominant species related to regime shifts. These results suggest the importance of proper consideration of temporal changes in the sampling scheme when analyzing long-term data. [ABSTRACT FROM AUTHOR]

Eastern Pacific populations of the leatherback turtle ( Dermochelys coriacea ) have declined by over 90% during the past three decades. The decline is primarily attributed to human pressures, including unsustainable egg harvest, development on nesting beaches, and by-catch mortality. In particular, the effects of climate change may impose additional stresses upon already threatened leatherback populations. This study analyzes how the pelagic habitat of Eastern Pacific leatherbacks may be affected by climate change over the next century. This population adheres to a persistent migration pattern; following nesting at Playa Grande, Costa Rica, individuals move rapidly through equatorial currents and into foraging habitat within the oligotrophic South Pacific Gyre. Forty-six nesting females were fitted with satellite tags. Based on the turtle positions, ten environmental variables were sampled along the tracks. Presence/absence habitat models were created to determine the oceanographic characteristics of the preferred turtle habitat. Core pelagic habitat was characterized by relatively low sea surface temperatures and chlorophyll-a. Based on these habitat models, we predicted habitat change using output from the Geophysical Fluid Dynamics Laboratory prototype Earth System Model under the Special Report on Emissions Scenario A2 (business-as-usual). Although the model predicted both habitat losses and gains throughout the region, we estimated that overall the core pelagic habitat of the Eastern Pacific leatherback population will decline by approximately 15% within the next century. This habitat modification might increase pressure on a critically endangered population, possibly forcing distributional shifts, behavioral changes, or even extinction. [ABSTRACT FROM AUTHOR]

The ingestion of microplastics (MPs - plastic particles <5 mm) by planktivorous organisms represents a significant threat to marine food webs. To investigate how seasonality might affect plastic intake in oceanic islands' ecosystems, relative abundances and composition of MPs and mesozooplankton samples collected off Madeira Island (NE Atlantic) between February 2019 and January 2020 were analysed. MPs were found in all samples, with fibres accounting for 89 % of the particles. MPs and zooplankton mean abundance was 0.262 items/m3 and 18.137 individuals/m3, respectively. Their monthly variations follow the seasonal fluctuation of environmental parameters, such as currents, chlorophyll- a concentration, sea surface temperature and precipitation intensity. A higher MPs/zooplankton ratio was recorded in the warm season (May-Oct), reaching 0.068 items/individual when considering large-sized particles (1000–5000 μm). This is the first study to assess the seasonal variability of MPs in an oceanic island system providing essential information respecting its ecological impact in pelagic environments. [Display omitted] • Abundance and composition of microplastics and zooplankton were analysed monthly. • Oceanographic processes and precipitation significantly affect these traits. • Fibres were the most abundant microplastic type found. • The microplastics/zooplankton ratio is greater in the warm season. • Seasonal variability might influence microplastics' ecological hazard. [ABSTRACT FROM AUTHOR]

The pelagic decapod crustacean fauna of two different zones (Sóller and Cabrera) with different hydrographic dynamics and oligotrophy levels was studied around Mallorca (western Mediterranean), the latter with a higher degree of oligotrophy than the former. Samples were taken with a Pelagic Trawl and an IKMT in the upper 600 m of the water column, targeting larger and middle-sized nektonic species, respectively. Fourteen species were collected: five dendrobranchiate shrimps, eight caridean shrimps and one scyllarid lobster. Some species were restricted to the shelf-break: Chlorotocus crassicornis and Plesionika heterocarpus . Others were exclusive of the middle slope: Pasiphaea multidentata , and Sergia robusta . Pasiphaea sivado and Gennadas elegans occurred in all pelagic strata. Multivariate analyses showed several distinct assemblages related to bathymetry and sampling depth. No significant differences were found concerning zone or sampled seasons. Bathymetrically, Deep Scattering Layers showed the highest diversity. No decapod crustaceans occurred in epipelagic daytime samples. The pelagic decapod community sampled was structured by both the geomorphology (and associated hydrographic characteristics over the shelf-break) and the influence of light in the water column. Size analysis showed species-specific patterns concerning size/age movements into the water column throughout the day–night cycle. [ABSTRACT FROM AUTHOR]

The structure and dynamics of cephalopod assemblages in different bathymetric strata from the surface to bottom grounds, down to a depth of 900 m, in the western Mediterranean, were analysed. Data were collected both on the shelf-break and slope during the summer and early autumn surveys, using a midwater trawl and a bottom trawl gear, to catch pelagic and nektobenthic species, respectively. The pelagic tows were not random, but targeted at the strongest and widest acoustic sound layers. A total of 26 cephalopod species belonging to 12 families were collected. With regard to the abundance, biomass and frequency of occurrence, we did not find a common seasonal trend for all the species, suggesting that their population dynamics are not governed by major environmental drivers. Most assemblage metrics (e.g., diversity, species richness, abundance and biomass) showed similar, low values in the pelagic layers compared to the bottom grounds. In general, assemblage metrics were lower in summer than in autumn on the shelf-break, while showing an inverse seasonal trend on the slope. There was a clear general increase in all metrics during the night compared to the day. Cluster results revealed differences in diel migratory strategies by stratum, vertical movements being scarce in the shelf-break species, but intense in the slope species. [ABSTRACT FROM AUTHOR]

Abstract: Sea bottom processes of the pelagic realm are still not completely understood and represent an intriguing subject. This paper focuses on the relationships between “normal” settling processes, redistribution of sediments and oceanographic parameters in a pelagic setting, during the Cenomanian. Five key Tethyian localities in the Cenomanian Umbria-Marche and Belluno Basins have been studied in order to understand the interplay among sea bottom processes that acted on the sea floor. The dataset consists of the mm-scale sedimentological description of the sections complemented by microfacies analysis on selected samples. Different sedimentological indications, such as presence of intraclasts, lined forams, pervasive plane-parallel lamination, suggest a continuous reworking under action of bottom-currents with varying intensity and direction. All the identified facies are here illustrated in detail and organized in a comprehensive schematic facies framework, the “facies matrix”, that leads to recognize two depositional facies suites: the “settling dominated” and the “traction current dominated”, under different oxygenation conditions. Our results suggest that settling of biogenic and inorganic particles represents the main source of pelagic sediments, but not the unique depositional process: under the action of sea-bottom currents of different intensity, sediments are continuously redistributed on the sea floor. All the collected evidences contribute to the proposal of a comprehensive depositional model for these reworked and redistributed fine-grained sediments, that represent true calcareous pelagic contourites. The model suggests that the identified traction-related facies can be used as a proxy for bottom current intensity and, indirectly, as an indicator of changing ventilation regimes at the sea floor through time. [Copyright &y& Elsevier]

Highlights: [•] Hierarchical, dynamic seascapes were classified using multivariate satellite data. [•] Seascapes describe basin and gyre scale features and seasonal boundary shifts. [•] Analyses of independent data reveal unique biogeochemical signatures among seascapes. [•] Dynamic seascapes result in more efficient pattern classification than static provinces. [•] Predicting pCO2 within seascapes reveals regional forcing and decreased model error. [Copyright &y& Elsevier]

In a paper entitled The paradox of the plankton , Hutchinson asked 'how it is possible for a number of species to coexist in a relatively isotropic or unstructured environment all competing for the same sorts of materials' (Hutchinson 1961 Am. Nat . 95 , 137-145 (doi:10.1086/282171)). Particularly relevant for phytoplankton, this paradox was based on two implicit, and perhaps naive, postulates, i.e. (i) that all plankton species have similar requirements and (ii) that the marine environment is relatively homogeneous in space and time. A number of hypotheses, based on purely theoretical or experimental studies, have been proposed to solve this conundrum, ranging from spatio-temporal environmental heterogeneity to biotic chaotic variability. Here, we characterize the ecological niche of 117 plankton species belonging to three different taxonomic groups and show that all species have a niche sufficiently distinct to ensure coexistence in a structured marine environment. We also provide evidence that pelagic habitats are, unsurprisingly, more diverse in space and time than Hutchinson imagined, the marine environment being neither unstructured nor stable in space and time. We, therefore, conclude that the niche theory, and its corollary the principle of competitive exclusion, apply as much for the plankton as for other forms of life, be they terrestrial or marine.

Abstract: Modelling was used as a tool to better understand the physical and biological processes observed during the multidisciplinary cruise DYNAPROC 2 (DYNAmic of rapid PROCesses in the water column), which took place in the Ligurian Sea in September–October 2004. The aim of the cruise was to study the short time-scale physical and biological processes that occur when the ecosystem switches from summer oligotrophy to autumnal mesotrophy. In this study, we have tested two 1D physical–biological coupled models. The first was a classical model in which surface layer dynamics were obtained using the turbulent kinetic energy model of Gaspar [Gaspar et al., 1990]. The simulated food-web took into account ten state variables: three nutrients, three classes of phytoplankton, two classes of zooplankton and two types of detritus. The second model (called IDA, Isopycnals Depth Adjustment) was based on the initial one but it took into account the measured variations of isopycnals depths. The results showed that the IDA model most efficiently reproduced the observed ecosystem dynamics. We have therefore used the IDA model to show that physical processes observed during the cruise had a major effect on biological compartment, mainly on nano- and picophytoplankton. [Copyright &y& Elsevier]

Abstract: A mass-balance trophic model was built to describe the food-web traits of the North Aegean Sea (Strymonikos Gulf and Thracian Sea, Greece, Eastern Mediterranean) during the mid-2000s and to explore the impacts of fishing. This is the first food-web model representing the Aegean Sea, and results were presented and discussed in comparison to other previous ecosystems modelled from the western and the central areas of the basin (South Catalan and North-Central Adriatic Seas). Forty functional groups were defined, covering the entire trophic spectrum from lower to higher trophic levels. Emphasis was placed on commercial invertebrates and fish. The potential ecological role of the invasive ctenophore, Mnemiopsis leidyi, and several vulnerable groups (e.g., dolphins) was also explored. Results confirmed the spatial productivity patterns known for the Mediterranean Sea showing, for example, that the total biomass is highest in N.C. Adriatic and lowest in N. Aegean Sea. Accordingly, food-web flows and several ecosystem indicators like the mean transfer efficiency were influenced by these patterns. Nevertheless, all three systems shared some common features evidencing similarities of Mediterranean Sea ecosystems such as dominance of the pelagic fraction in terms of flows and strong benthic–pelagic coupling of zooplankton and benthic invertebrates through detritus. The importance of detritus highlighted the role of the microbial food-web, which was indirectly considered through detritus dynamics. Ciliates, mesozooplankton and several benthic invertebrate groups were shown as important elements of the ecosystem linking primary producers and detritus with higher trophic levels in the N. Aegean Sea. Adult anchovy was shown as the most important fish group in terms of production, consumption and overall effect on the rest of the ecological groups in the model, in line with results from the Western Mediterranean Sea. The five fishing fleets considered (both artisanal and industrial) had high impacts on vulnerable species and numerous targeted groups given the multispecies nature of the fisheries in the N. Aegean Sea. Several exploitation indices highlighted that the N. Aegean Sea ecosystem was highly exploited and unlikely to be sustainably fished, similarly to other Mediterranean marine ecosystems. [Copyright &y& Elsevier]

Abstract: We examined the mesoscale distribution of zooplankton populations using a continuous recording system: the optical plankton counter (OPC). Data were collected in the mid-latitude northeast Atlantic inter-gyre region in April and September 2001 during the POMME 2 and POMME 3 cruises. This sector of the North Atlantic system is characterized by subduction phenomena and mesoscale eddies. Estimated mean biomass was 2.88DWgm−2 in April and 1.64DWgm−2 in September with populations dominated by small copepods of the genera, Clausocalanus, Paracalanus and Oithona. Day–night changes in vertical distribution appeared to be seasonally variable. During April, absolute concentrations within the upper layer above 50m were higher at night. During September, vertical profiles of relative biomass were quite similar for day and night. Highest depth-integrated biomasses were located mainly on the periphery of anticyclonic eddies, with maxima related to the increase in depth range of vertical distribution. This pattern suggested that maximum biomass was associated with the most dynamic parts of the frontal features. Other zones of high zooplankton biomass were associated with the centers of cyclonic eddies and high fluorescence values. Using a 3D view, we found that zooplankton distribution showed a more complex pattern than in a 2D view with variable vertical distribution. Hence, proper description of the distribution of zooplankton underlines the need to describe this submesoscale with an order of magnitude around 10 nautical miles. [Copyright &y& Elsevier]

The platy limestone (plattenkalk) deposit of Vallecillo in northeastern Mexico is widely known for its well preserved and diverse fish and marine reptilian assemblage dated to the early–middle Turonian (Late Cretaceous). A single specimen of the pachyrhizodont G. roberti revealed the first Cretaceous isopod (Crustacea, Arthropoda) attached to a fish host. Preservation allows for the interpretation of the entire body and most appendages. A parasitic lifestyle of the isopod is inferred based on the specimen's morphology including claw-like dactyli, but is also inferred based on the anoxic bottom conditions variously interpreted for the Vallecillo plattenkalk deposit, which excluded scavengers. The individual is here referred to the family Cymothoidae and described as Mothocya vallecillae n. sp. • First Cretaceous record of a parasitic Isopod associated with the fish host. • First Isopod record from Vallecillo. • Claw-like dactyli allow being assigned to Cymothoidae. • The Vallecillo individual is interpreted as a new species, Mothocya vallecillae. [ABSTRACT FROM AUTHOR]

Abstract: Spatial distribution, egg production and growth of the predominant euphausiids in the vicinity of the Pribilof Islands, Bering Sea, were studied during August 2004. Thysanoessa longipes was abundant in the oceanic water, aggregations of Thysanoessa inermis were observed both in the oceanic region and on the shelf near the Pribilofs, while Thysanoessa raschii was found near the islands. Euphausia pacifica and Thysanoessa spinifera occurred in much smaller quantities in the oceanic water. Euphausiid abundances on the middle shelf were several orders of magnitude lower than in the cold summer of 1999. The instantaneous growth rate (IGR) technique was applied to measure somatic growth. Juvenile T. inermis showed the most intensive growth (∼8% of dry body weight per day). In contrast, the somatic growth of mature specimens of both T. inermis and T. raschii was slow (<1% of dry body weight per day) suggesting the investment of resources into seasonal lipid deposition and reproduction. Egg release corresponded to an average of 1.1% of female dry body weight per day for T. raschii, indicating that enough resources were available for the animals to maintain reproductive activity. Our data suggest that the area near the Pribilofs, known for its high biological productivity, may provide a refuge for the shelf euphausiid population during warmer summers, when conditions on the shelf are unfavorable for their growth and reproduction. [Copyright &y& Elsevier]

Abstract: Interannual variability in abundance of the dominant euphausiids Thysanoessa inermis, Thysanoessa spinifera and Euphausia pacifica was studied in the northern Gulf of Alaska during the production season from 1998 to 2003. T. inermis abundance increased significantly over the shelf from 1998 to 2002, the abundance of T. spinifera (which also inhabits the shelf) did not change, while the abundance of E. pacifica (usually common on the outer shelf) declined in 2001. Based on the incidence of spermatophores on the females, reproduction of T. inermis occurred during April in all years, and was extended through May in 2000–2002. The major spawning of T. spinifera and E. pacifica occurred from April through July, and from late May through August, respectively. The spawning of T. inermis and T. spinifera appeared to be closely related to the spring diatom bloom on the inner shelf, while the spawning of E. pacifica occurred later in season, when the temperature of the mixed layer increased. A strong increase in abundance of T. inermis, associated with the extended colder phase in the North Pacific, indicates that progressive cooling in 1999–2002 may have resulted in greater reproductive success of the early spawning T. inermis on the inner shelf. [Copyright &y& Elsevier]

Abstract: Vertical profiles of nitrate uptake were obtained in pelagic waters of the western North Pacific. Uptake rates were determined by a conventional, particulate-based 15N tracer method with in situ incubations for 24 h. Among the five profiles reported in this paper, three of them are obtained at one station in the subarctic Pacific (45°N, 165°E) on different occasions, and two of them are obtained at stations in the subtropical Pacific (25°N, 165°E and 25°N, 170°E). Nitrate uptake sharply decreased with depth at the subarctic station. At the subtropical stations where nitrate concentrations in surface waters were low, 15N-nitrate was added both at a trace level (ca. 4 nM–8 nM) and at a saturated level (ca. 8 μM). Uptake of the trace 15N varied less pronouncedly with depth, and the rates were slightly higher in the upper 70 m. Uptake of the saturated 15N was substantially higher in the upper 50 m and decreased with depth. No uptake near the depths of nitracline or deep chlorophyll maximum was larger than those at other depths in the euphotic zone. The estimated depth-integrated uptake rates were 0.97–1.22 mmol N m−2 d−1 at the subarctic station and 0.36–0.54 mmol N m−2 d−1 at the subtropical stations. [Copyright &y& Elsevier]

Conspecific predation among longnose lancetfish Alepisaurus ferox was investigated in four spatio-temporal strata of the western Indian Ocean. The cannibalism level varied from 0 to 45.5% by frequency of occurrence and was negatively related with abundance of non-evasive prey (such as crustaceans Charybdis smithii and Natosquilla investigatoris) and foraging success. Predation by lancetfish is often described as a non-selective process, constrained by local prey availability and by its feeding speed during an attack of prey. Our results show that lancetfish may adapt its opportunistic foraging behavior, feeding on non-conspecific abundant prey such as crustaceans when available, and switching to a high level of conspecific predation in poor waters. [ABSTRACT FROM AUTHOR]

This paper investigates the impacts of different turbulence models on the biological state at an ocean station in the northern Adriatic sea, named S3, comparing them with other uncertainties inherent to coupled physical-biological simulations. The numerical tool is a 1-D model resulting from the coupling of two advanced numerical models. The hydrodynamic part is modelled using the General Ocean Turbulence Model (www.gotm.net), in a version adopting state-of-the-art second-moment Turbulence Closure Models (TCMs). Marine biogeochemistry is parameterized with the Biogeochemical Flux Model (http://www.bo.ingv.it/bfm), which is a direct descendant of ERSEM (European Regional Sea Ecosystem Model). Results, obtained by forcing the model with hourly wind and solar radiation data and assimilating salinity casts, are compared against monthly observations made at the station during 2000-2001. Provided that modern second-moment TCMs are employed, the comparisons indicate that both the physical and the biological dynamics are relatively insensitive to the choice of the particular scheme adopted, suggesting that TCMs have finally 'converged' in recent years. As a further example, the choice of the nutrient boundary conditions has an impact on the system evolution that is more significant than the choice of the specific TCM, therefore representing a possible limitation of the 1-D model applied to stations located in a Region of Freshwater Influence. The 1-D model simulates the onset and intensity of the spring-summer bloom quite well, although the duration of the bloom is not as prolonged as in the data. Since local dynamics appears unable to sustain the bloom conditions well into summer, phytoplankton at the station was most likely influenced by river input or advection processes, an aspect that was not found when the S3 behaviour was adequately modelled using climatological forcings. When the focus is in predicting high-frequency dynamics, it is more likely that lateral advection cannot be neglected. While the physical state can be satisfactorily estimated at these short time scales, the accurate estimation of the biological state in coastal regions still appears as rather elusive. [ABSTRACT FROM AUTHOR]

Abstract: The behaviour of southern elephant seals from Kerguelen Island (, ) was investigated in relation to the oceanographic regions of the Southern Ocean. The oceanographic and the seal behaviour data, including location and diving activity, were collected using a new generation of satellite-relayed devices measuring and transmitting pressure, temperature, and salinity along with locations. Dive duration, maximum diving depth, time spent at the bottom of the dives, and shape of dive profiles were compared between male and female seals, and were related to the oceanographic characteristics of areas prospected by the seals. Most animals travelled to the Antarctic shelf. However, during winter, adult females travelled away from the continent, remained and foraged within the marginal sea-ice zone, while juvenile males remained within the pack ice to forage mainly on the Antarctic shelf. Therefore, as the ice expanded females appeared to shift from benthic to pelagic foraging farther north, while males continued to forage almost exclusively benthically on the continental shelf. This difference is likely related to the different energetic requirements between the two sexes, but also may be related to pregnant females having to return to Kerguelen in early spring in order to give birth and successfully raise their pups, while males can remain in the ice. Our results show an important link between elephant seals and Antarctic sea ice and suggest that changes in sea-ice conditions could strongly affect the behaviour of this species. [Copyright &y& Elsevier]

Abstract: There has been an interest in the application of Sr/Ca ratios in pelagic carbonates to reconstruct paleoceanographic conditions such as changes in the oceanic Ca and Sr budgets or calcareous nannoplankton productivity, but the effect of burial diagenesis on primary Sr/Ca records has not been sufficiently understood. In order to clearly document Sr/Ca records of pelagic carbonates relative to original paleoceanography or secondary diagenetic processes, Sr/Ca analyses were performed on bulk sediments from an 822.5m-thick ooze–chalk–limestone sequence at the Mid-Pacific Mountains, Deep Sea Drilling Project Site 463. The Sr/Ca ratios exponentially decrease from ∼2.3 to ∼1.1mmol/mol with increasing burial depth in the ooze–chalk interval (0–452.0m below seafloor (mbsf)). The Sr/Ca ratios further decline to as low as ∼0.4mmol/mol in the limestone interval (>452.0mbsf), with relatively high values of >1.1mmol/mol at carbonate-poor lithology around 620mbsf. The stratigraphic Sr/Ca trends appear to be consistent with porosity profile, and similar Sr/Ca—porosity covariation in association with diagnetic changes in lithologies is also common in Ontong Java Plateau sections. By adopting a recent diagenetic model from backscattered electron image analysis of Ontong Java Plateau sections, it is postulated for Site 463 that exponential Sr/Ca decrease in the ooze–chalk interval is due to the release of Sr into interstitial water via recrystallization (i.e., purification effect), and that further decrease in Sr/Ca ratios in the limestone interval is most likely due to acquisition of Sr-depleted calcite cement at the ‘chalk–limestone transition’ (newly proposed as the dilution effect). Specifically, Sr/Ca ratios of deeply buried pelagic limestones are sensitive to the amount of calcite cement that is acquired in proportion to CaCO3 content; i.e., carbonate-rich lithology facilitates precipitation of secondary calcite at the chalk–limestone transition. Therefore, paleoceanographic interpretation by means of Sr/Ca ratios in pelagic carbonates will become valid only when these diagenetic effects are appropriately constrained. [Copyright &y& Elsevier]