Characterizing nesting traits and egg incubation thermal environments at sea turtle rookeries establishes a critical baseline for population conservation and targeted nesting habitat management. Here, we conducted continuous monitoring of green turtles (Chelonia mydas) nesting at Ganquan Island, Xisha Islands (South China Sea) throughout 2018–2020 to investigate the nesting ecology, nest thermal profiles, and seasonal hatchling sex ratio dynamics. Over the three monitoring years, the annual mean number of nests (clutches) was 60.3. Nesting activity extended from April to December, with a pronounced breeding peak occurring July–September. Mean nest temperatures recorded between April and August surpassed the upper thermal optimum for embryonic development. We determined the pivotal temperature to be 29.4 °C; across the complete nesting cycle, hatchling sex ratios were strongly female-skewed, with females accounting for 78.4
Males adopting alternative reproductive tactics (ARTs) often face uneven sperm competition, leading to asymmetrical pressures on ejaculate expenditure. These asymmetries are further influenced by spatio-temporal variations in fertilization context, such as where and when males release sperm relative to female oocytes. In loliginid squids, females have two spatially separated fertilization sites (internal oviduct opening and external buccal membrane) associated with consort and sneaker tactics, respectively. Males with alternative phenotypes, therefore, face asymmetrical pressures both in sperm competition and fertilization context. Consort males have long been predicted to dominate paternity due to their access to the internal site, making it difficult to understand the role of sneakers, whose sperm are stored at the buccal membrane. Using the loliginid Doryteuthis pleii, we empirically obtained evidence that fertilization sites dictate male success. Sperm at the oviduct monopolizes fertilization when spawning females have sperm at both sites. This clarifies long-standing enigmas regarding squid ARTs. For example, previous studies showed that sneakers have lower sperm investment per mating than consorts – our results indicate that this strategy could be associated with the lower availability of unfertilized oocytes at the buccal membrane. Conversely, when females lack sperm at the oviduct, the last sneaker to mate sires most offspring. This indicates that while the buccal membrane provides long-term sperm storage for several sneaker males, last-male sperm precedence ultimately dictates fertilization success at the external site, revealing complex postcopulatory sexual selection at the buccal membrane. Overall, these results corroborate the critical importance of fertilization context in the evolution of ARTs and highlight loliginid squids as excellent models to test how fertilization environment and sperm competition asymmetries shape diverging adaptations in male ARTs.
Understanding of how submesoscale processes and climate variability influence net primary productivity (NPP), total particulate organic carbon (POC) flux, and diatom-contributed organic carbon (Corg_diatom) in the southern Gulf of California remains limited. This study examines the relationship between organic carbon production and export, with an explicit focus on the transfer of Corg_diatom from the surface to the sediment-trap depth in the Alfonso Basin. Data collected from 2008 to 2012 reveal that Corg_diatom flux accounted for 52
Adriatic Sea represents the largest neritic foraging ground for loggerhead sea turtles (Caretta caretta) within the Mediterranean Sea. As ectothermic organisms, loggerhead sea turtles in Adriatic Sea inhabit seasonally dynamic thermal environment with winter sea temperatures as low as 7 °C. Despite the ecological and conservation significance, the space use strategies employed as a response to thermal variation remain poorly understood. We tracked 21 loggerhead sea turtles, of which 10 were small juveniles with < 45 cm curved carapace length. We quantified individual movement patterns and seasonal space use relative to sea surface temperature. Two space use strategies were identified: some turtles remained resident year-round in northern foraging and overwintering areas, while others undertook long-distance southward migrations, with overwintering concentrated within a thermal range of 11–15 °C for both groups. The persistence of loggerhead sea turtles in such conditions suggests greater plasticity in thermal tolerance and winter habitat use than previously assumed. Individuals occupied small areas in the coldest period (January–February) during overwintering and in the warmest period (July–October) during foraging, while the most extensive space use was observed in the transitional period from cold to warm (March–April). Our study provides first insights into the spatial ecology of small juveniles in the Mediterranean Sea and expands the limited body of knowledge on the wintering biology of the species.
Global climate change is reshaping marine ecosystems through interacting shifts in temperature, pH and food availability, yet how these stressors jointly influence organismal plasticity remains insufficiently resolved. This study examines how warming, ocean acidification and food limitation interact to affect two important drivers of plasticity: fatty acid (FA) composition and DNA methylation in the benthic harpacticoid copepod Platychelipus littoralis. Copepods were collected in March 2025 at 51.20 °N, 3.43 °E and exposed to factorial combinations of the three stressors. Temperature consistently emerged as the dominant driver of physiological change: warming reduced total FA concentrations, increased saturation and decreased essential long-chain n-3 polyunsaturated FAs, including eicosapentaenoic acid (EPA, 20:5n-3). Acidification and food limitation had weaker main effects but produced several context-dependent interactions: under low food availability, acidification reduced EPA levels, while warming combined with either acidification or food limitation increased n-3/n-6 ratios. When all three stressors co-occurred, arachidonic acid (ARA, 20:4n-6) increased, elevating the ARA/EPA ratio, a marker of physiological stress. Global DNA methylation increased under both warming and acidification, with an antagonistic interaction between them, whereas the three-stressor combination produced the highest methylation levels. Together, these results demonstrate that warming is the primary driver of FA depletion and epigenetic modification in P. littoralis, while acidification and food limitation reshape or amplify these temperature-driven responses. These integrated biochemical and epigenetic shifts show how multiple stressors simultaneously challenge organismal plasticity through metabolic regulation, with consequences for its energetic resilience and fitness of P. littoralis under future-climate conditions.
Hydrogen isotope ratios (δ2H) are widely used to study animal movement and food web energetics. However, unexplained, non-geographically derived δ2H variation can limit the accuracy and resolution of δ2H-based interpretations. We examined potential causes of δ2H variation–including age, body size, and amino acid (AA) factors–in a non-migratory Cocos booby (Sula brewsteri) colony around Islas Marietas, Mexico (20°41′N, 105°36′W) in 2016–2018. We also explored the applicability of novel AA δ2H data as high-resolution tracers for biosynthesis and food web dynamics in the marine realm. Among the 87 birds in our study, the δ2H values of plasma from chicks (< 45 days old) and feathers from juveniles (grown from 40–70 days old) both increased with age by > 25‰, and plasma δ2H correlated with body size in both chicks and adults. Proline δ2H values exhibited a striking range (over several hundred per mille), were the predominant AA driver of patterns in bulk plasma δ2H values (r2> 0.6 for chicks, > 0.8 for adults), and correlated with body size and chick age. Based on our dataset, we predict that Threonine δ2H values may indicate marine versus terrestrial resource use, Alanine δ2H values may reliably reflect environmental water, and Serine δ2H values may retain a marine basal food signal in carnivores. We suggest future studies carefully consider the influence of body size and age while interpreting δ2H datasets. Furthermore, we contend that AA δ2H data hold an untapped cache of ecological and physiological information that should be exploited to better understand δ2H propagation through food webs and refine the utility of this isotopic tool.
Some migratory procellariiform (tube nosed) seabirds can dive to depth yet the physiological mechanisms underpinning their dive performance remain poorly described. We compared dive capacity traits (total oxygen stores, theoretical aerobic dive limit (tADL) and muscle buffering) in three species of Procellariiformes that spanned a range of dive behaviour, i.e., grey-faced petrel (Pterodroma gouldi, x̄ dive depth/duration: 1.6 m, 4 s), flesh-footed shearwater (Ardenna carneipes, x̄ dive depth/duration: 3.5 m, 6.9 s) and the sooty shearwater (Ardenna grisea, x̄ dive depth/duration: 6.9 m, 39.7 s). Our results show that the deeper and longer diving shearwaters have significantly higher total oxygen stores than grey-faced petrels i.e., 41.0 ± 3.1 mL O2 kg− 1 for grey-faced petrels versus 46.2 ± 2.3 and 48.6 ± 2.2 mL O2 kg− 1 sooty shearwaters and flesh-footed shearwaters respectively. This is mirrored in respective tADL times with 44.2 ± 3.4 s for grey faced petrels, versus 49.6 ± 2.7 and 52.3 ± 2.4 s for sooty shearwaters and flesh-footed shearwaters respectively. Furthermore, dive logger data indicates that these species would rarely exceed tADL. Myoglobin concentrations in pectoral muscles of our study species correlated strongly with diving ability. This myoglobin oxygen supply appears sufficient to keep metabolism of flight muscles aerobic as muscle buffering capacity differed minimally among species. Lastly, temporal differences in haematological parameters suggest a plasticity in blood oxygen stores among years. Our results show the degree to which physiological adaptations meet function, with Procellariiformes exhibiting traits that match their underwater performance.
Reproduction is a key process shaping the population dynamics and ecological impact of gelatinous zooplankton. In the ctenophore Mnemiopsis leidyi, temperature is widely considered a key driver of reproductive success, yet its relationship with reproductive output (RO) has rarely been evaluated experimentally across a broad thermal gradient. Here, laboratory experiments were conducted to examine how temperature influences whether individuals reproduce and their RO across a range of 7–27 °C. Adult individuals were collected in Mar del Plata Harbour (Argentina) during the spring-summer seasons (2023–2025). Reproduction was rare or absent at temperatures ≤ 10 °C, but occurred consistently between 15 and 27 °C, supporting the existence of a lower thermal threshold for reproduction in M. leidyi. Above this threshold, RO remained highly variable, and no consistent relationship between RO and temperature was observed under the short-term experimental conditions. These findings indicate that temperature influences whether reproduction occurs, while variation in short-term RO above the thermal threshold is likely driven by additional biological and ecological factors.
Nest relocation and shading are widely used conservation strategies intended to mitigate threats to marine turtle hatchling survival. However, these interventions may carry unintended fitness costs. Estimating such effects can be challenging, especially in the absence of opportunities to compare with natural, undisturbed nests. Green turtle (Chelonia mydas) clutches were assigned to one of three treatments (in situ, shaded relocation, or unshaded relocation) on Heron Island, Queensland, Australia (23.44307° S, 151.91809° E), during two nesting seasons (Dec 2022 – Feb 2023 and Dec 2023 – Feb 2024). Incubation temperature, hatching and emergence success, sex ratio, morphology (carapace size and body mass), and performance (self-righting ability and crawl speed) were assessed. Relocated unshaded nests exhibited higher incubation temperatures than in situ and shaded nests, especially during the final two weeks of incubation. Consequently, warmer nests produced smaller hatchlings with higher mass relative to size (residual mass) and poorer self-righting performance. Notably, in situ and shaded relocated nests had comparable incubation temperatures, yet still differed in hatching success, hatchling size, and self-righting ability, indicating that relocation can carry developmental consequences independent of those related to thermal averages. These findings highlight the importance of prioritising in situ nesting where feasible and accounting for both thermal and non-thermal factors of relocation sites if relocation is required.
Oceanic whitetip sharks (Carcharhinus longimanus) have undergone marked population declines due to overexploitation. Abundance trends typically rely on fisheries-dependent data that can be biased, particularly for protected species, as legal protections may influence compliance in capture reporting, likely leading to under- or inaccurate reporting. Fishery-independent methods offer complementary insights but traditional surveys (e.g., longlines) can be costly and difficult to implement. Here, we evaluated pelagic Baited Remote Underwater Video Stations (pBRUVS) to establish relative abundance indices for oceanic whitetips using both free-drifting and boat-tethered configurations. Across two sampling periods (April–May 2023 and 2024), we deployed 99 pBRUVS off of Cat Island, The Bahamas between Columbus Point ( 24°07′ N, 75°17′ W), and Tartar Bank ( 24°02′ N, 75°28′ W) where oceanic whitetips were detected on 51.52
Understanding tropical seabird foraging strategies is essential for evaluating ecosystem functioning within Very Large Marine Protected Areas (VLMPAs). We investigated spatial and trophic behavior of brown booby (Sula leucogaster) at the Saint Peter and Saint Paul Archipelago (SPSP), a remote breeding site within a VLMPA in the equatorial Atlantic Ocean. Using GPS tracking from 207 individuals (706 trips, 2014–2015 and 2023–2024), stable isotopes (δ13C and δ15N) from 58 blood samples, and 49 regurgitated samples, we assessed variation in foraging effort and diet across sex, breeding stage, and temporal scales. Despite pronounced reversed sexual size dimorphism, no intersexual differences were detected in movement parameters. However, females exhibited significantly higher δ15N values, indicating subtle trophic segregation. Breeding stage showed minimal influence, suggesting that extreme nest density and continuous territorial defense override intrinsic reproductive demands. Pronounced interannual variation in foraging effort was detected, with 2023 showing nearly double the ranges compared to 2015. Seasonally, trip metrics did not differ, but time allocation shifted between austral winter and summer: traveling decreased (48.1
This study investigates isotopic variability in two abundant black coral species from the Great Reef of Toliara (GRT), southwestern Madagascar: Cirrhipathes anguina, a tall whip coral, and Cupressopathes abies, a shorter, branched bottlebrush coral. Using stable isotopes of carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S), we examined inter- and intraspecific dietary variation and intracolonial isotopic gradients. Colonies were collected on the outer slope (20–28 m depth) of the northern pass of the GRT, an area influenced by tidal currents and terrestrial sediment discharge. Sulfur and carbon isotopes provided limited resolution for distinguishing the isotopic niches of the two species but indicated reliance on oceanic planktonic production rather than lagoonal or terrestrial sources. Significant isotopic differences occurred between species: Ci. anguina exhibited higher δ¹⁵N values, reflecting a higher trophic position and consumption of larger prey (mesozooplankton) than Cu. abies, which likely feeds on smaller plankton and particulate organic matter. Ci. anguina displayed a broader trophic niche and greater δ¹⁵N variability, suggesting a more flexible diet. No vertical isotopic gradients were detected within colonies, implying no trophic specialization along colony height. However, δ¹⁵N variability within Ci. anguina colonies suggests opportunistic feeding behavior. Overall, this study highlights the role of morphology in shaping feeding strategies and demonstrates clear trophic niche partitioning that facilitates coexistence. Intracolonial isotopic homogeneity supports single-point sampling, although intercolonial variability warrants caution in interpreting δ¹⁵N-based trophic ecology.
The species identification of whales, dolphins and porpoises at sea remains challenging, particularly for cryptic species like beaked whales (Family: Ziphiidae). Here we use environmental (e)DNA for identification of Sato’s beaked whale, Berardius minimus, at sea. This species was first described in 2019 and, to date, all but one genetic sample has been collected from beachcast carcasses. Sato’s beaked whales are difficult to distinguish at sea from the larger Baird’s beaked whales (Berardius bairdii), highlighting the need for reliable methods to identify this species in the field. Using high-throughput metabarcoding of the mtDNA control region, we confirmed visual identification of Sato’s beaked whales in six of the eight eDNA samples collected in the Nemuro Strait. One of the samples also provided a haplotype consistent with a killer whale. From the samples of Sato’s beaked whales, we recovered three of the five previously described haplotypes and resolved two novel variants. These haplotypes have the potential to further describe diversity and population structure in this elusive whale. Our results demonstrate the potential of eDNA metabarcoding as a non-invasive tool for detecting and assessing the genetic diversity of Sato’s beaked whales and other deep-diving cetaceans.
Several land crab species inhabit oceanic islands worldwide, where they often dominate terrestrial arthropod communities, and act as ecosystem engineers. In the South Atlantic, Johngarthia lagostoma is the only gecarcinid species, endemic to Rocas Atoll, Fernando de Noronha, Ascension, and Trindade. Despite its classification as ‘Endangered’, there is a gap in knowledge on the spatial and temporal distribution of this species. Here, we investigated the population density and habitat preferences of J. lagostoma on Trindade Island, Brazil, examining the influence of dune vegetation sectors, diel activity, and environmental variables (elevation, relative humidity, and distance from the sea). Crabs were sampled weekly across three vegetated dune areas during both day and night, over eight weeks. No significant variation in sex ratio or size was detected among areas, although males were consistently larger than females. Crab density varied significantly with vegetation dune sector and diel period. Daytime density was highest in intermediate areas where two plant species co-occurred, and crabs remained sheltered, whereas nighttime density increased closer to the shoreline during feeding activity. Elevation, humidity, and mean carapace width were positively associated with density during the day, explaining 42
Kelp forests are considered foundational species in coastal ecosystems worldwide and are recognized as nursery areas that help maintain the structure of fish assemblages. In southern hemisphere marine ecosystems, giant kelp forests Macrocystis pyrifera, play a crucial role in the ecological dynamics of the fish assemblages, a role that has been documented with some clarity. However, in Chilean Patagonia, it remains poorly understood, especially with regard to the spatio-temporal variation in fish assemblages and kelp forests. The present study is one of the first to identify the structural role of kelp forests in relation to associated fish assemblages across broad seasonal and spatial scales in southern Patagonia. Four sites were studied on the coast of the Tierra del Fuego archipelago with presence of M. pyrifera forests, each under contrasting environmental conditions. Seasonal sampling was carried out by autonomous diving, identifying and enumerating all fish species within 1 m on each side of a 25 m transect line (50 m²) and recording the population and morphometric variables of the M. pyrifera forest. Morphometric variables were determined at each site to estimate wet biomass (kg/ind. and kg/m²) in these ecosystems of kelp forests. Our results show a positive correlation between increases in fish richness (14 species) and abundance in M. pyrifera, mainly during the austral summer. These results reaffirm the structural role of M. pyrifera forests in shaping fish assemblages and underscore the urgency of establishing robust, permanent marine conservation measures for these forests, which are scarcely protected in southern Patagonia.
Atmospheric heatwaves are increasing in frequency and intensity. Understanding coastal ecosystem responses and the potential for thermal refugia from these events is critical for evaluating the ecological consequences of climate change. In intertidal marine sediments, eagle ray feeding creates pits in the sediment that can retain water at low tide. These pits could buffer against atmospheric heat stress, providing functional refugia for organisms and maintaining ecosystem function. We investigated the role of ray pits as refugia by simulating a 4-day heat stress event on an intertidal flat in Aotearoa New Zealand. We compared ecological responses to heat stress between ambient sediments and ray pits by measuring benthic oxygen fluxes as well as explanatory covariates of cockle density and burrowing behaviour, and sediment characteristics. We found that heat stress caused smaller temperature increases in pits compared with ambient sediments, but this did not influence oxygen fluxes. Instead, we found that reduced cockle densities in pits corresponded with a shift in the relationship between cockle density and net oxygen production (photosynthesis minus respiration). Heat stress did not alter the direction of this relationship, but increased variability around it for both ambient and pit sediments. Measurements of cockle burrowing behaviour indicated that heat-stressed cockles burrow faster across all sediments, which could drive this increased variability in their influence on net oxygen production. Overall, our experimental results show that while ray pits buffer sediment temperature extremes slightly, they do not provide functional refugia from heat stress.
The haptophyte Phaeocystis globosa is a common harmful algal bloom (HAB) species in Chinese coastal waters with negative impacts on fisheries and energy security. However, the small size of P. globosa single cells makes them particularly challenging to detect, making it hard to monitor cell densities before bloom development. Regular PCR and qPCR-based detection methods have been effective but such methods require equipment that is not readily available on site. Hence, an efficient detection method for the rapid and sensitive identification of P. globosa is highly demanded. In this study, a recombinase polymerase amplification (RPA) and lateral flow dipstick (LFD)-based technology was developed for the rapid detection of P. globosa cells. A pair of RPA primers and an LFD probe were designed targeting the P. globosa-specific molecular marker pgcp1, which was developed based on chloroplast genome variations of P. globosa. RPA reaction conditions were optimized to 39℃ and 20 min. Results indicated that RPA-LFD could specifically detect P. globosa, and the RPA-LFD assay exhibited higher sensitivity than regular PCR-based assays, with a detection limit of 8.65 × 10–2 ng/μL for genomic DNA, 5.88 × 103 copies/μL for recombinant plasmid DNA, and 3.23 cells/mL for cell density. The practicality of this assay for on-site detection has also been verified through the environmental samples collected from the Beibu Gulf. In conclusion, the RPA-LFD method developed in this study shows great potential for early monitoring of P. globosa in the field due to its strong specificity, high sensitivity, convenient operation and rapid visualization.
Cold-stunning is a well-established hypothermic condition in sea turtles associated with exposure to low water temperatures. However, the effects of cold air exposure on post-emergent sea turtle hatchlings crawling from their nest to the ocean remain poorly documented. This report documents the first case of terrestrial cold-stunning in the peer-reviewed literature. Here, we use the term terrestrial cold-stunning to describe prolonged cold-induced immobility in sea turtle hatchlings following emergence onto the nesting beach, resulting in mortality or requiring intervention. On 11 November 2025, following a cold snap in Florida (USA), 335 green sea turtle hatchlings (Chelonia mydas) exhibiting terrestrial cold-stunning were encountered along a 4-km stretch of the Archie Carr National Wildlife Refuge, central east Florida (between 28.026666/-80.537448 and 27.99272/-80.52031). Hatchlings were collected under permitted protocols and gradually rewarmed; 68.7
Gorgonian corals are common members of hardbottom benthic communities worldwide, from shallow reefs to the deep sea. Most species exhibit upright branched colonies with polyps adapted for feeding on particles from flowing seawater. Some shallow-water gorgonian species maintain photosynthetic zooxanthellae, which provide an additional source of nutrition. Does dissolved organic material (DOM) in seawater represent another potential food source for gorgonians? In this study, we used laboratory incubation experiments to test the ability of 7 species of gorgonians to draw down 2 different sources of labile DOM from seawater: an amino acid mixture and a monosaccharide mixture. Experiments were performed using 3 azooxanthellate species (Muricea pendula, Swiftia exserta, Thesea nivea) and 4 zooxanthellate species (Antillogorgia bipinnata, Eunicea flexuosa, Plexaura homomalla, Pterogorgia anceps). There was net DOM drawdown for 2 of 4 zooxanthellate species incubated with the amino acid mixture in both darkness and light, measured as a change in dissolved organic carbon (DOC) after a 6 h incubation. There was no net drawdown of the monosaccharide mixture by any gorgonian species. Differences in DOM drawdown across gorgonian species could not be attributed to differences in colony fragment wet mass or polyp oral disk surface area. These results are contrary to past consensus views of the capacity of invertebrate epithelia to draw down DOM, possibly due to different analytical techniques. DOM augmentation is unlikely to be useful in gorgonian propagation for restoration.
Understanding resource partitioning and niche segregation is crucial for explaining coexistence among seabirds. During the breeding season, colonial seabirds, such as storm-petrels, act as central-place foragers and face strong competition for resources. This study focused on intersexual niche segregation and interspecific differences in two sympatric storm-petrel species, the Black Storm-petrel (Hydrobates melania) and Leach’s Storm-petrel (H. leucorhous chapmani), breeding on San Benito Oeste Island (28°18’12” N, 115°35’24” W), Baja California, Mexico, in the Eastern Pacific. Fieldwork was conducted during the chick-rearing period in 2022. Foraging movements and main foraging areas of chick-rearing adults were determined by GPS tracking, and prey composition was identified using DNA metabarcoding of faeces and regurgitate samples. The results show that intersexual segregation differed between species and was not equally evident across niche dimensions. In Leach’s storm-petrels, molecular diet analysis revealed no evidence of dietary segregation between sexes. In Black Storm-petrels, by contrast, the sexes showed a tendency towards dietary differences, accompanied by sex-specific differences in foraging movements. Furthermore, the findings indicated distinct resource partitioning strategies between species: Black Storm-petrels primarily foraged in neritic waters, whereas the single tracked Leach’s Storm-petrel used oceanic waters. In addition, gastrointestinal parasites were documented for both species. This study contributes to the understanding of niche segregation in colonial seabirds and highlights the importance of integrating spatial and dietary components when studying resource partitioning in avian communities.
