Analyzing trends in leatherback turtle Dermochelys coriacea reproductive success provides insights into species fitness and responses to environmental pressures, including changes in temperature and beach characteristics. Despite the Gulf of Guinea hosting the world’s largest leatherback nesting aggregation, reproductive success data in the region remain limited, with most studies focusing on the northwestern Atlantic and Pacific populations. Bioko Island, Equatorial Guinea, in the southeastern Atlantic, ranks second in the Gulf of Guinea for leatherback nesting encounters after Gabon. Over 9 nesting seasons, we assessed hatching and emergence success of in situ leatherback nests on 2 key nesting beaches along Bioko’s southern coastline (Beach E: 2008-2014; Beach D: 2016-2019) and explored the relationship between nest temperature and success rates. Overall, good hatching success was (mean ± SE) 0.27 ± 0.03, and emergence success was 0.21 ± 0.02, both lower than global averages (0.55 ± 0.17 and 0.48 ± 0.19, respectively). Success rates varied significantly between beaches: Beach D had higher hatching (0.64 ± 0.07) and emergence success (0.56 ± 0.08; n = 21) compared to Beach E (0.21 ± 0.03 and 0.16 ± 0.02, respectively; n = 125), and interannual variation occurred on Beach E. Temperature data suggest that beach slope and precipitation are likely to have contributed to these differences. Our findings contribute valuable insights into leatherback reproductive success in the southeastern Atlantic, highlighting Bioko’s importance for regional populations. Addressing geographic biases and identifying reproductive trends inform global conservation efforts and underscore spatiotemporal variation in a key nesting area.

Tropical reef fish are especially sensitive to ocean warming, and the impacts of warming on reproduction may influence the persistence of future populations. The capacity of phenotypes to match altered conditions depends on the nature of environmental change, such as timing, duration, and variability. However, little is known about how these characteristics alter the plasticity of reproduction. The present study investigated how the timing of warming (+1.5°C above present-day temperature) through early development (hatching-1.5 yr) and/or post-maturation (1.5-3 yr) impacted reproduction and offspring quality in a tropical damselfish (Acanthochromis polyacanthus). Warming at both life stages affected adult morphometrics and reproduction differently, but offspring quality was not impacted by parental thermal experience. Specifically, warming during development resulted in smaller adults (shorter standard lengths) with significantly reduced fecundity, while warming after maturation led to lighter adults for a given length that produced smaller eggs. This study also highlighted that fish may be able to partially restore their reproductive output in elevated temperatures with extended experience of warming after maturation. However, negative impacts from developing in elevated temperatures remained even in their second breeding season when fish were 3 yr old. Such knowledge of how aspects of temperature change influence environmental sensitivity and the capacity for plasticity is important to understand the drivers of species’ resilience to change.

Effective monitoring and reporting of fisheries are crucial for successful management and are typically done by at-sea observers and fishers, respectively. However, this system can produce biased information due to economic and social limitations. Electronic monitoring and reporting systems (EMRs) are becoming more prevalent and are seen as a solution to combat illegal, unreported, and unregulated fishing. The present study aimed to test the effectiveness of an integrated EMR in identifying demersal and deep-sea sharks, skates, and chimaeras (hereafter chondrichthyans), which are bycatch in the Portuguese crustacean bottom trawl fishery. Footage (42 h) was thoroughly examined and provided identification of 2182 individuals representing 11 taxa. The majority were identified to the genus level, and some even to the species level. Only 0.9% of the chondrichthyans could not be identified. Furthermore, the highest bycatch rates of chondrichthyans were from the genera Etmopterus and Galeus. The limitations of the technology are discussed, and suggestions for improvement are made to enhance future research proposals and improve the overall design of the system. However, the successful implementation of the EMR in this study and other case studies worldwide demonstrates its potential for upscaling to other fisheries, contributing significantly to more sustainable fishing practices and better management of marine resources.

We completed multiple-stable isotope analyses (δ13C, δ15N, and δ34S) of Adélie penguin Pygoscelis adeliae chick-bone collagen to characterize differences in foraging behavior among 15 colony locations across the Ross Sea region. Foraging behavior was represented by δ13C, δ15N, and δ34S values and classified into groups using k-means cluster analyses. Additionally, we report the first stable isotope values for the Adélie penguin colony on Sabrina Island, Balleny Islands. Cluster analyses revealed distinct isotopic signatures for the northernmost and central colonies; however, owing to spatial and temporal variability, isotopic signatures were not strong enough to distinguish the southernmost colonies. Results also indicated that δ15N values increased with latitude (66-77° S), corresponding to higher krill consumption at colonies that foraged in sensible heat polynyas or the open ocean and increased fish consumption for those foraging in latent heat polynyas to the south. Generally, δ34S values are used to distinguish foraging grounds, specifically inshore/offshore foraging or foraging over the continental slope versus the continental shelf, in marine animals. Although the southern and central colonies currently forage along the continental shelf and the northern colonies forage over the shelf, slope, and/or open ocean, we found no significant difference in δ34S values among colonies. While a positive correlation between δ15N and δ34S values was evident, δ34S signatures did not exhibit distinct patterns specific to individual colonies or regions. The absence of a clear trend reflecting inshore/offshore foraging underscores the need for additional research to bridge this knowledge gap.

Increasing attention has been devoted to understanding the responses of oyster populations to natural disasters such as hurricanes. In particular, the recruitment of planktonic oyster larvae is crucial to the recovery and sustainability of oyster populations and, by extension, oyster fisheries. In this study, a bioenergetic model was developed to explore the spatio-temporal dynamics of larval recruitment for the eastern oyster Crassostrea virginica within the Galveston Bay System of Texas, USA. Further, model simulations were performed for a case study under post-hurricane (2018) and normal (2021) scenarios, aiming to elucidate the response mechanisms of oyster larvae to the hurricane disturbance. Our results demonstrate a strong post-hurricane recovery of planktonic oysters in 2018. Simulated larval recruitment was much higher in the middle-lower Galveston Bay and West Bay compared to the upper Galveston Bay and East Bay. By using simulation results, we further quantified the planktonic habitat suitability for oyster larvae to support future oyster management and restoration. This study contributes to the quantitative assessment of oyster resilience and adaptation in the face of the escalating threat of hurricanes amidst climate change and provides a framework for future coupling of an individual-based model with a biophysical model to enhance understanding of oyster larval dispersal and population connectivity.

Intraspecific trait variation, whether phenotypic or due to genotypic differences, can influence ecosystem functioning, especially in the case of ecosystem engineering species. Here, we investigated a coastal ecosystem dominated by 2 distinct genetic lineages of the native brown mussel Perna perna in 2 biogeographical regions along the South African coastline. Both euendolithic corrosion and genetically based behavioural differences have been shown to improve the microclimate of mussel beds and thus reduce abiotic stress for associated macrofauna. We therefore hypothesized that euendolithic corrosion of mussel shells, and its interactions with known genotypic variation, would affect the bioengineering capabilities of mussels on the rocky shores. Two manipulative field experiments revealed that macrofaunal communities differed significantly between experimental sites, reflecting the effects of biogeography and regional patterns in species distribution. Unexpectedly, neither euendolithic corrosion nor its interaction with P. perna genetic lineages influenced macrofaunal community structure. In marine bioengineered habitats, the associated macrofauna respond differently to intraspecific trait variations in the engineer depending on their own sensitivity to environmental stressors. In addition, this influence is limited to the spatio-temporal context in which trait variations have an effect. Although intraspecific trait variation was previously demonstrated to influence ecosystem processes in mussel beds, regional/biogeographic effects were more important in determining the composition of the associated macrofauna. Identifying the relative influence of genotypic and phenotypic intraspecific trait variation versus biogeography and large-scale processes on both ecosystem engineers and their associated communities is required to predict their ecosystem-level consequences for coastal communities under the effects of global climate change.

Cold seeps host oasis-type ecosystems sustained by microorganisms such as chemosymbiotic bacteria, fueled by reduced gasses like hydrogen sulfide and methane. These habitats are characterized by a wealth of carbon and nutrient sources, substantial microbial turnover of key nutrients, and unknown metabolic interactions between symbionts and their hosts. Thus, the trophic ecology of cold seeps is not fully understood. Recent discoveries of massive shark nurseries and extensive chemotones in the southeastern Mediterranean Sea (SEMS) hint at a previously unknown complexity of food webs in this habitat. To provide insights into the trophic ecology of SEMS seeps, we collected symbiont-bearing (Lamellibrachia anaximandri tubeworms, Idas modiolaeformis mussels, and Lucinoma kazani clams) and other fauna, such as eggs of Galeus melastomus sharks, Gracilechinus elegans echinoids, Clelandella myriamae gastropods, and Calliax lobata ghost shrimps, from the Palmahim Disturbance seeps (~1000-1150 m water depth, Levantine basin in the SEMS). We obtained bulk and compound-specific values (δ13C and δ15N), using isotope ratio mass spectrometry and compound-specific isotopic analysis of amino acids. Glutamic-acid-phenylalanine trophic position (TPGlu-Phe) and the contribution of reworked organic matter (microbial resynthesis index, ΣV) were estimated for individual specimens. Our findings indicate a wealth of nutrition strategies and trophic interactions, as chemosynthetic productivity and external sources sustain these communities. Collagen-rich eggs of G. melastomus appear to sustain the opportunistic detritivores/carnivores such as G. elegans (maximum TPGlu/Phe = 4.7; higher than that of G. melastomus, maximum TPGlu/Phe = 3.8), but also supplement the chemosynthetic nutrition of Idas mussels, likely through heterotrophic symbionts.

The Canadian lobster Homarus americanus industry faces the challenge of minimizing bycatch (discarded lobster and non-target species) while optimizing catch rates in a quota-managed fishery. This study assessed the effect of varying soak times (2-14 d) on trap catches off the southwest coast of Nova Scotia. In a 1 yr, controlled, industry-led trial, the most comprehensive study of bycatch in the Canadian lobster industry, soak times were representative of commercial operations, and electronic monitoring provided independently validated data. Employing mixed logistic regressions, a significant correlation was found between extended soak times and increased risk of capturing cusk Brosme brosme and unidentified bycatch species (not specifically monitored), while no significant associations were observed for white hake Urophycis tenuis, Jonah crab Cancer borealis, Atlantic cod Gadus morhua, and rock crab Cancer irroratus. The overall impact of soak times on estimated bycatch weights for cusk and unidentified species was minor compared to more influential factors such as fishing area, depth, and temporal trends. Reducing soak times may decrease cusk and unidentified bycatch but would lead to a substantial reduction in landed lobster, requiring increased fishing efforts. Historical evidence, from regular independent at-sea observer coverage and government analysis, emphasizes that fleet rationalization and footprint concentration through trap reduction exerted a larger impact on bycatch rates than the observed changes from soak time alterations in the study. Acknowledging such historical insights will be helpful for planning strategies for mitigating bycatch in lobster trap fisheries taking place in similar environmental and operational conditions.

The gut microbiome of the benthic copepod Platychelipus littoralis, a key species in the intertidal mudflats of western Europe, was characterized throughout a 1 yr period. It was hypothesized that benthic copepods living in sediment would have core microbial taxa in their gut microbiome, in accordance with the gut microbiomes of pelagic copepods living in the water column, but that this community might change rapidly. Copepods were isolated from sediment, and after a starvation period, the guts were microdissected. The copepod gut was found to be a selective microbial microhabitat, significantly different in microbiome composition from the sediment, with lower species richness and evenness. Although microbial cell counts were low in copepod guts, the gut microbiome was stable between 24 and 48 h of egestion. Diatoms were the main food source of the copepods, as confirmed by fatty acid biomarkers. Core bacterial species in the gut belonged to Rhodobacteraceae, Flavobacteriaceae and Saprospiraceae, known as degraders of complex organic compounds. Bacteria were not a significant food source themselves, but core bacterial taxa were potentially involved in food-assisted degradation. This study elucidated bacteria-copepod interactions, relevant for the food web ecology of benthic systems and potentially the optimization of copepod culturing.

Development of habitat occupancy models for protected species with low detection rates can be difficult; however a possible solution is to use proxy species. In the San Francisco Bay-Delta estuary, detection of the endemic and endangered Hypomesus transpacificus is extremely rare despite extensive survey efforts. We applied a tree-based machine learning algorithm to evaluate habitat characteristics associated with detection of H. transpacificus using paired data from a pelagic fish survey and a lower-trophic monitoring study. Preliminary analysis using only H. transpacificus data produced a model with limited predictive ability; models combining H. transpacificus with a closely related species, H. nipponensis, or a broader set of potential surrogate pelagic fishes were better supported. The catch per unit volume (CPUV) of the small pelagic fish community (SPFC) was the strongest explanatory variable for both H. transpacificus and combined H. transpacificus-H. nipponensis detections, indicating shared habitat use among multiple species in the estuary. Salinity and zooplankton prey density had the highest relative influence on SPFC CPUV. These results indicate that H. nipponensis and the SPFC are utilizing similar habitats as H. transpacificus and may therefore serve as appropriate proxies for H. transpacificus in habitat modeling or other monitoring and analysis. This finding also suggests the potential that H. transpacificus may compete with multiple species for limited food resources within small patches of high-quality habitat; the consequences of such dynamics on species recovery is identified as an important topic for future research.

This ex situ study utilised oxygen microprofiling and whole-core incubations to investigate potential changes in oxygenation of cohesive sediments resulting from open-ocean fin-fish farming. We examined oxygen conditions in sediments subjected to potential moderate depositional loads (1.1, 2.2, and 3.2 g C m-2 d-1) of organic farm particles from mariculture expected to settle in dispersive environments. White biofilms formed over particulates that accumulated on the sediment surface after 7 d of at least 2.2 g C m-2 d-1. Diffusive oxygen uptake (DOU) rates were estimated from sediment microprofiles taken in cores following total oxygen uptake (TOU) determination from whole-core incubations. DOU closely aligned with TOU (DOU:TOU ≈ 1) in cores where biofilms did not develop on the sediment surface (<1.1 g C m-2 d-1); however, the development of biofilms reduced the DOU:TOU ratio (<1), suggesting the biofilms were responsible for non-diffusive oxygen transport in the TOU. It was speculated that ‘vents’ in the biofilms may have enhanced the solute exchange rates in those cores. The presence of biofilms enhanced benthic TOU, reducing oxygen penetration depths in sediments adjacent to the biofilms by approximately 1 mm compared to unenriched cores. However, these sediments adjacent to biofilms still had an average oxygen penetration of ~2.5 mm, suggesting the patchy accumulation of organic farm particles and development of biofilms on the sediment surface are enhancing the structural heterogeneity of the seafloor and increasing the availability of organic carbon for higher trophic consumers in an otherwise organically deplete system.

Evaluating how emergent technologies can complement traditional methods for detecting wildlife is particularly valuable when population management is based on detection-based metrics for rare or cryptic species of conservation need. The black-footed ferret (ferret; Mustela nigripes) is an Endangered species whose rarity and behavior (e.g. semi-fossorial and nocturnal) challenge our ability to monitor individuals and assess the status of populations. Here, we evaluated how applying the emergent technologies associated with thermal-infrared cameras can be used to detect ferrets in a reintroduced population on the Fort Belknap Indian Reservation, Blaine County, Montana, USA. We conducted nighttime surveys for ferrets using thermal-infrared cameras mounted to a tower and unmanned aerial vehicles (UAVs). We recorded 7 ferret observations using a stationary tower at a rate of 0.43 observations per survey hour. At least 5 individual ferrets were observed using this method for a rate of 0.31 individuals observed per survey hour. Similarly, we recorded 8 ferret observations using UAVs for an observation rate of 0.41 observations per survey hour. At least 6 individual ferrets were observed using this method for a rate of 0.31 individuals observed per survey hour. Our findings suggest that the use of thermal-infrared cameras could benefit conservation and management efforts for the ferret or other similar species, providing a tool for detecting these elusive species that creates less disturbance to the landscape and alleviates potential navigation challenges associated with ground-based survey methods. The use of thermal-infrared cameras deployed as described here could therefore serve to complement traditional survey techniques for this Endangered species.

In the 1970s, the discovery of the problem of the hole in the ozone layer represented a crucial milestone in the history of science and the environment. Scientists such as Mario Molina and F. Sherry Rowland revealed that chlorofluorocarbons (CFCs), previously thought to be harmless, could destroy the ozone layer, leading to global awareness of environmental protection. However, they faced resistance from industry and misinformation. Confirmation of the problem came with Jonathan Shanklin’s work in Antarctica. The effects of ozone depletion, such as increased skin cancer, were documented, and humanity reacted with the Montreal Protocol, phasing out harmful substances. Furthermore, the link between the historical success of science-based environmental actions and the modern challenges posed by misinformation should be emphasized, especially considering the rise of digital platforms as both tools and threats to public understanding. Today, tackling disinformation in global environmental problems represents a substantial challenge, requiring science education, raising awareness on social media, valuing traditional sources, training in source verification, recognizing science as a reliable source, and tackling environmental challenges based on science. This article proposes actionable solutions such as integrating critical media literacy into education, establishing international regulations to curb disinformation, and leveraging collaborative platforms to promote accurate scientific communication. It argues that strengthening international cooperation, modeled on the Montreal Protocol, is crucial to countering misinformation and fostering effective global environmental policies. The history of the Montreal Protocol highlights the importance of science, international cooperation, and determined action in protecting the environment and human health.

Hard-bottom habitats at mesophotic depths have the potential to serve as refuges from climate change, but they are understudied. Anthropogenic structures, including shipwrecks, provide critical habitats for hard-bottom-obligate invertebrates and structure-oriented fishes. A key question in marine ecology and the emerging interdisciplinary field of Maritime Heritage Ecology is how the structure of a shipwreck influences the biological community inhabiting it. To answer this question, we analyzed video recordings from 4 shipwrecks and 3 naturally occurring hard-bottom reefs in the mesophotic zone in the northern Gulf of Mexico/Gulf of America. We tested the influences of habitat size, distance between sites, and type (shipwreck or natural reef) on species richness, community composition, and functional composition of invertebrates and fishes. For both shipwrecks and natural hard-bottom reefs, our results showed a significant influence of habitat size on species richness for invertebrates but not for fishes. All factors had significant relationships with community composition and functional composition. Larger shipwrecks provided vertical relief and overhangs, which were rare on natural reefs and supported pelagic predators and sessile invertebrates, respectively. Shipwrecks hosted the non-native sun coral Tubastraea coccinea and regal demoiselle Neopomacentrus cyanomos, likely because of the microhabitats they provided. Our study demonstrates the important role that shipwrecks play in supporting biodiversity in the mesophotic zone but also highlights the possibility that they could facilitate the spread of non-native species.

Decomposition pathways of detritus are key processes in the contribution of macroalgal habitats to natural carbon sequestration of ‘blue carbon’. The anaerobic decomposition of 3 North-east Atlantic canopy-forming kelp species was investigated using ex situ decomposition chambers. Thallus parts (stipes, holdfasts and blades) of Laminaria hyperborea, Saccharina latissima and L. digitata were incubated in still seawater in temperature-controlled dark conditions. Refractory potential (Rp), first-order decomposition rate (k) and associated half-life (t1/2) were calculated. Dissolved organic and inorganic carbon (DOC and DIC, respectively) were measured in the incubation water at 0, 7, 14 and 21 d, and thermal gravimetric profiles were determined at each decomposition stage. Oxygen depletion occurred within 24 h. Approximately 5 times as much DOC was released than DIC. Holdfast material produced the most DIC, while blade material released the greatest amounts of DOC. S. latissima released less DOC than L. hyperborea and L. digitata. The mean (SD) Rp of fragments increased from 0.46 ± 0.05 to 0.50 ± 0.04 throughout the 21 d incubations. S. latissima had the highest Rp throughout. First-order decomposition rates, averaged across the 3 kelp species, gave half-lives (t1/2) for blade fragments of 27.8 ± 2.9 d, (k = 0.025 ± 0.002) and stipes as 113.2 ± 21.1 d (k = 0.006 ± 0.001). This experiment clarifies the fate of macroalgal carbon during early decomposition and thus the processes that govern blue carbon pathways of macroalgae, highlighting the differences in breakdown among different species and thallus parts.

Rapid environmental changes in high-latitude marine ecosystems have led to warmer ocean temperatures and shifts in zooplankton abundance, community composition, and life history. Variations in zooplankton abundance and phenology (inferred changes in egg production timing and differences in developmental rates that result in changes to observed life stage composition) are tightly coupled to climate processes. Furthermore, zooplankton represent a critical trophic foundation for commercially valued fish communities. To better understand how zooplankton phenology has responded to recent climate perturbations, we used generalized additive models to examine changes in life stage composition for 2 copepod species groups in the Eastern Bering Sea—Calanus spp. (C. glacialis and C. marshallae) and Neocalanus spp. (N. plumchrus and N. flemingeri)—across a 20 yr time series. We found that annual shifts in Calanus spp. and Neocalanus spp. phenology are mediated by temperature and spring southwesterly wind frequency. Specifically, warmer temperatures and reduced spring southwest wind frequency were associated with younger copepod life stages, suggesting an earlier spring phenology. We also tested if an extended zooplankton growing season has enabled the production of a second Calanus spp. generation. We found evidence of earlier spring Calanus spp. reproduction and observed high proportions of younger life stages in the fall, suggesting a second generation in some warm years. Collectively, these results suggest fundamental climate-linked changes to copepod phenology and reproduction, which impact the population dynamics of copepods and could consequently disrupt elements of the Bering Sea trophic structure that rely upon these energetically dense species.

Arctic and sub-Arctic ecosystems are experiencing changes in environmental conditions, altering marine biodiversity through shifts in species distributions and composition. Coastal ecosystems in northern environments are vulnerable to continued environmental change, but the remoteness of these areas and challenges associated with sampling shallow, structurally complex habitats have limited studies on nearshore communities. We compared the composition and relative abundances of nearshore assemblages in 7 coastal locations spanning 10° latitude of boreal and sub-Arctic habitats in Newfoundland and Labrador, Canada, using baited remote underwater video (BRUV). We identified 14 taxa, including 11 fish species and 3 decapod crustaceans. Species richness and diversity was generally higher in southern relative to northern locations, and spatial distributions differed across taxa. Greenland cod Gadus macrocephalus ogac and large cottids Myoxocephalus spp. were the most common taxa in northern areas and the only species observed across the entire environmental gradient. In contrast, we observed Atlantic cod G. morhua, winter flounder Pseudopleuronectes americanus, and cunner Tautogolabrus adspersus exclusively in southern locations. In addition to community variability across locations, habitat differences contributed more to variation in community-level abundances than to the abundances of most individual taxa. BRUVs provided an effective method for comparing nearshore assemblages across northern coastal habitats that are challenging to other common sampling methods. Further studies incorporating BRUVs could track variability in nearshore assemblages over longer time scales and offer an accessible method for coastal communities to monitor change across habitats.

The porbeagle shark Lamna nasus, a top predator in the North Atlantic, is vulnerable to anthropogenic stressors due to its life history characteristics. Understanding its biology, abundance and spatial ecology is crucial for underpinning effective conservation and management strategies. We collected satellite tag data from 10 porbeagle sharks caught off the north coast of Ireland to study migration behaviour and space use. Data from pop-up satellite archival tags and platform terminal telemetry tags collected between July 2010 and February 2014 (for deployments up to ~9 mo) showed long-distance (1479-25707 km), seasonal migrations, with autumnal movements along the shelf-break to regions around Portugal, the Bay of Biscay and the Azores via the Mid-Atlantic ridge. Migrations to waters off Norway and the Faroe/Shetland Islands were also evident prior to these autumnal southward migrations. In spring, some sharks returned northwards, and there was evidence of site fidelity for shelf waters around the northern Irish coast and western Scotland and the Celtic Sea in summer. Porbeagles exhibited seasonal changes in vertical space use as they traversed various habitats during migration, with deeper occupancy of the water column in winter than in summer. There was a distinct day-night pattern in porbeagle depth distribution during their off-shelf residency in winter, consistent with diel vertical migrations between deep waters in daytime and the surface layers at night. Nocturnal depth distribution was closely associated with the lunar cycle, with deeper residency/diving occurring during periods of full moon. Porbeagles occupied and traversed both the open ocean and coastal areas of high fishing activity, highlighting the challenge of managing this stock because of large-scale migratory behaviour.

Deep-sea hydrothermal vents are extreme, isolated, and ephemeral ecosystems populated by unique endemic fauna, making them a potentially challenging setting for the survival of parasites with indirect (multi-host or ‘complex’) life cycles. We examined the animal communities at a frequently disturbed hydrothermal vent field (9°50’N, East Pacific Rise) to explore whether parasites with indirect life cycles complete their life cycles within this island-like, ephemeral marine habitat, which has been previously hypothesized but is not known. Our dissections of individuals from 51 vent species revealed 7 morphogroups of parasitic flatworms (trematodes) including the genera Biospeedotrema, Caudotestis, and Neolebouria, and 4 life stages in the multi-host trematode life cycle. Adult trematode life stages lived in the vent fishes Thermarces cerberus and Thermichthys hollisi, while the intermediate life stages were found in a variety of crustacean, gastropod, and polychaete species. Genetic barcoding of the 18S, 28S, and ITS2 regions linked sequential life stages for some of the morphogroups, revealing the phylogenetic position and routes of transmission between hosts for vent trematodes. This study provides the most direct evidence yet that parasites very likely complete indirect life cycles in deep-sea hydrothermal vent ecosystems, with important implications for the persistence and diversity of parasites in disturbed environments.

New Zealand sea lions Phocarctos hookeri were once widespread on New Zealand’s coasts but were hunted to remnant populations in the Subantarctic islands during expansion of European settlements. In contrast, New Zealand fur seals Arctocephalus forsteri maintained their widespread distribution, persisting at remote colonies. The resource niche positions of these species provide insights on structure of underlying food webs and contribution of alternate sources of organic matter to ecosystem function. We measured changes in their resource niche positions with stable isotope analysis (δ13C, δ15N and δ15NAA) of bone collagen from first Māori settlement (1250-1450 CE), middle European expansion (1650-1850 CE) and modern (2016 CE) time periods. Samples from each time period were collected from the Subantarctic islands, central region and from reestablishing sea lion populations on the mainland South Island. In the Subantarctic islands, high trophic positions were maintained through time but divergence in the resource niche of the 2 species between pelagic and benthic food webs occurred in the modern time period, consistent with resource limitation. In the central and mainland regions, both species declined in trophic position during the modern time period. In the central region, the 2 species maintained distinct resource niche discrimination while in the mainland region, they converged in the modern time period, consistent with high overlap on a reduced diversity of low trophic level pelagic prey. These patterns provide a unique view of the long-term changes in trophic relationships between marine top predators during the full history of human occupation in New Zealand.

Most marine ecosystems are experiencing increasing cumulative impacts from climate change, fishing, shipping and land-based pollution. The resulting ecosystem responses are challenging to monitor. Studying the space use of top marine predators may provide insight into how these ecosystems react to these impacts. However, natural populations are composed of unique individuals that differ in many ways, including how they use space. Here, we used data from a multidecadal biotelemetry research program on grey seals in the Northwest Atlantic to investigate temporal changes in space use in the context of environmental changes and increasing population size. We quantified temporal changes in monthly home range size, shape and distribution of grey seals in the Gulf of St. Lawrence between 1992 and 2022, while also quantifying interindividual differences. We found that the monthly home ranges of grey seals have increased in size and shifted in distribution over the last 3 decades, indicating that the seals appear to have expanded their space use. We detected individual differences in mean home range characteristics and their level of variability, suggesting that individual identity plays a role in the large-scale space use of grey seals. We also found negative correlations between the mean and level of variability in both home range size and shape, hinting at the potential presence of different tactics within the population. This study highlights how top marine predators can modify their behaviour to adapt to environmental changes and illustrates the importance of considering interindividual differences when exploring population space use patterns.

Understanding predator-prey relationships is essential for revealing the complex role of marine mammals in exerting top-down control within marine ecosystems and is crucial for developing effective conservation strategies. The harbour porpoise Phocoena phocoena is the most abundant cetacean species in the North Sea, and most studies on its diet are based on traditional hard part analysis in stomachs providing limited knowledge of its complex feeding ecology. Here, we combined stomach content analysis (SCA), metabarcoding and stable isotope analysis on the same 48 individuals, stranded between 2005 and 2021, to elucidate the diet of harbour porpoises in the southern North Sea. We aimed to increase prey species detection rates and to uncover temporal changes in the diet by comparing individual diets immediately prior to stranding with assimilated diets. By using SCA and metabarcoding complementarily, we were able to increase species detection by 49% on an individual sample level and uncovered a previously unknown prey species, hooknose Agonus cataphractus. Adult harbour porpoises primarily obtain energy from common sole Solea solea and sandeels, while juveniles rely mainly on whiting Merlangius merlangus, reflecting distinct energy sources aligned with biomass estimates. Direct method comparison revealed great temporal dietary differences in adult and juvenile porpoises. Near-shore species with a benthic carbon source contributed most to the short-term diet, whereas offshore species with a pelagic carbon source contributed most to the long-term diet. This framework can be extended to other ecosystems and predator species to elucidate the species-specific diets of animals where direct observations are not feasible.

Environmental fluctuation dictates life cycles in many ecosystems on earth, especially within marine coastal areas. The magnitude of those fluctuations at ecologically relevant time scales (i.e. hours and days) induces phenotypical adjustment in aquatic organisms, including maternal investment in offspring. However, the effect of the magnitude and the periodicity of those fluctuations on animal physiology has been poorly investigated. In this study, we investigated the correlation between environmental fluctuation and maternal investment in offspring. We focused on one population of the kelp crab Taliepus dentatus from central Chile and considered whether fluctuations in water temperature, dissolved oxygen and salinity are associated with temporal changes in maternal investment in early embryos (volume, lipid content and fatty acid composition) over a period of 1 yr. We used remote data loggers deployed at an ecologically relevant temporal scale to calculate the monthly magnitude, periodicity and predictability of environmental fluctuations. We found substantial variation among females in embryo volume, lipid content and fatty acid composition during the year, mostly associated with seasonality (average environmental conditions). However, embryo lipid content and essential fatty acids (arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid) showed a clear negative relation with the monthly predictability of the environmental fluctuations. This study shows how the integration of environmental fluctuations and their predictability can improve our understanding of the reproductive ecology of marine coastal species.

Climate change is regarded as a major threat to seabird populations globally. While the impacts on certain species are well-studied, the majority remain understudied, which may limit our understanding of the key mechanisms linking climate change to population dynamics. This information is important to identify vulnerable species and inform potential conservation responses. To address this gap, we reviewed literature on the impacts of climate change on the demography of 25 seabird species breeding in the UK and Republic of Ireland from relevant studies conducted within the wider North-East Atlantic. We found regional and species-specific variations in research effort, with the North Sea being the most studied area. The most frequently studied species were common guillemot Uria aalge (n = 35), black-legged kittiwake Rissa tridactyla (n = 29), and European shag Gulosus aristotelis (n = 25). Breeding productivity and population abundance were the primary demographic parameters investigated. The North Atlantic Oscillation and sea surface temperature were commonly used to describe climate influences, often linked to bottom-up mechanisms affecting demography through changes in prey availability. Breeding productivity was the most monitored demographic rate across species; this may lead to important mechanisms affecting other demographic rates, such as survival, being overlooked. Regional and species-specific disparities in research could bias the identification of key mechanisms. Despite these uncertainties, current literature highlights the importance of climate impacts through the food chain and severe storm events affecting seabirds. In response, climate change adaptation should prioritise management of fish stocks near breeding colonies and coastal management to protect vulnerable colonies from storm events.