Marine Biology最新文献

The growth properties and environmental adaptability of different corals and symbionts vary. Therefore, insights from the adaptive mechanisms of Symbiodiniaceae in corals are very meaningful. In this study, we surveyed the seawater characteristics at three sites on Luhuitou fringing reef, Hainan Island (China), sampling three native corals Pocillopora damicornis, Acropora hyacinthus, and Galaxea fascicularis on 27 September 2021. The photo-physiological (Fv/Fm, Y(II), α, and rETR) were measured, and high-throughput sequencing of Symbiodiniaceae ITS was performed. The Luhuitou site had the lowest temperature (28.845 °C ± 0.01), salinity (33.967 ± 0.03), and pH (8.468 ± 0.05) among the three sites. The Sanya site contained significantly the highest ammonium (7.406 μmol/L ± 1, P < 0.05). The nitrate of the Xiaozhou site was 1.5 times significantly higher than the other two sites. Three corals and their Symbiodiniaceae were adapted differently. P. damicornis showed more plasticity and was dominant by Cladocopium sp. C1d at high-ammonium habitat. A. hyacinthus was dominated by Cladocopium (C3 and C1232) and they had the lowest Fv/Fm (0.595 ± 0.02) in poor integrated water quality environments (the Xiaozhou site) among three corals, suggesting that the less adaptation. G. fascicularis established a stable symbiotic relationship with Durusidinium sp. D1, and they had a more stable symbiotic system and were better suited for long-term reef restoration. Our results provide a deeper understanding of the environmental adaptations of three corals at the Luhuitou fringing reef. Meanwhile, it provides a perspective application for coral transplantation species selection in restoring local reef ecology in the future.

Mapping spatial variation in stable isotope values (isoscapes) of primary producers and consumers can provide insight into regional patterns of biogeochemistry and be used to trace the movements of mobile animals. Here we present carbon (δ¹³C) and nitrogen (δ¹⁵N) isoscapes for an expansive region of the continental United States (Mid Atlantic Bight to the NW Gulf of Mexico) derived from inshore lizardfish (Synodus foetens) and explore temporal stability and environmental drivers of observed isotopic variation. We observed significant spatial variation in lizardfish δ¹³C and δ¹⁵N values throughout much of the Atlantic and Gulf coasts, reflecting local biogeochemistry regimes. Extensive sampling throughout the northern Gulf of Mexico (NGOM) revealed positive relationships between lizardfish δ¹³C values and bottom temperature, likely reflecting lower carbon isotope discrimination between CO₂ and phytoplankton in highly productive, warm, inshore environments. Conversely, δ¹⁵N values were not well explained by environmental parameters, but appeared higher in nearshore environments of the NGOM, which are heavily influenced by nitrogenous run-off from land. An isotopically unique region of high δ¹³C values and low δ¹⁵N values were observed for lizardfish sampled in the Eastern NGOM off the southwest coast of Florida, reflecting a potential influence of seagrass and/or macroalgal productivity supporting the base of the food web. Overall, these findings underscore the utility of benthic lizardfish stable isotopes for inferring local patterns of ocean biogeochemistry throughout expansive ocean environments. In application, these data can be used to define migratory histories of mobile taxa and support contemporary critical habitat assessments.

Understanding spatial heterogeneity in reproductive success among at-risk populations facing localised threats is key for conservation. Sea turtle populations often concentrate at one nesting site, diverting conservation efforts from adjacent smaller rookeries. Poilão Island, Bijagós Archipelago, Guinea-Bissau, is a notable rookery for green turtles Chelonia mydas within the João Vieira-Poilão Marine National Park, surrounded by three islands (Cavalos, Meio and João Vieira), with lower nesting activity. Poilão’s nesting suitability may decrease due to turtle population growth and sea level rise, exacerbating already high nest density. As the potential usage of secondary sites may arise, we assessed green turtle clutch survival and related threats in Poilão and its neighbouring islands. High nest density on Poilão leads to high clutch destruction by later turtles, resulting in surplus eggs on the beach surface and consequently low clutch predation (4.0%, n = 69, 2000). Here, the overall mean hatching success estimated was 67.9 ± 36.7% (n = 631, 2015–2022), contrasting with a significantly lower value on Meio in 2019 (11.9 ± 23.6%, n = 21), where clutch predation was high (83.7%, n = 98). Moderate to high clutch predation was also observed on Cavalos (36.0%, n = 64) and João Vieira (76.0%, n = 175). Cavalos and Meio likely face higher clutch flooding compared to Poilão. These findings, alongside observations of turtle exchanges between islands, may suggest a source-sink dynamic, where low reproductive output sink habitats (neighbouring islands) are utilized by migrants from Poilão (source), which currently offers the best conditions for clutch survival.

Foraging animals move through the environment to satisfy their requirements for food, rest, reproduction and risk-avoidance. Understanding how animals respond to changing environmental conditions can help to characterise favourable habitat and determine whether they might be motivated to depart when those habitats become unsuitable. Foraging green turtles are typically residents that scarcely move in response to environmental changes or disturbances. Some individuals though, exhibit high mobility at fine scales. We developed an analysis of Fastloc GPS tracks of 61 green turtles using cox regression models and generalised linear mixed models to investigate the influence of a suite of environmental characteristics on the length of residence time and probability of turtles transitioning between two behavioural modes, “stay” or “go”. Decisions to move (“go”) were influenced by short-term changes in the local environmental conditions. Individuals were more likely to “stay” when temperature increased during their stay and were more likely to “go” when turbidity decreased, and they entered deeper habitats. This result implies that foraging and resting (“staying”) primarily occurs in benthic, shallow, warm habitats, while transit (“going”) is facilitated in deeper, clear water. We also determined that individuals within the green turtle foraging aggregation respond differently to environmental cues to move and hypothesise that a diversity of strategies within a foraging aggregation could confer its resilience to disturbance events. Our study provides new evidence of the factors influencing movements in green turtles and can aid in predicting how they may respond to future changes and enhance risk mitigation efforts through dynamic and adaptive planning.

In both terrestrial and marine ecosystems, prey species exhibit various reactions to predators, including avoidance, fighting and freezing. Acoustic communication associated with mobbing has been depicted in numerous tetrapod species. This sonic behaviour remains however largely unknown in fish although mobbing has been shown in different coral reef fish as a response to predation risk. This study focused on the communication strategy of prey species in the presence of predators. We tested the reaction of the holocentrid Sargocentron caudimaculatum when facing a moray eel and compared the sounds they produced against the predator with sounds produced when the fish are hand-held, recorded in standardized conditions. When introduced in mesocosms to a moray eel, S. caudimaculatum produced distinct distress sounds, resembling staccato calls, and swam towards the predator with their heads pointed in its direction and their dorsal fin erected. This observation supports a mobbing behaviour with specimens shifting from an escape behaviour to an aggressive response in presence of predator. Moreover, these sounds are different from those emitted during manual handling. This difference in acoustic signal suggests the coexistence of multiple warning/alarm sounds in this species. Holocentrids can produce different kinds of sounds witnessing their ability to provide graded information based on the perceived predation risk. We suggest that species of this family would be a suitable and promising group with which to test the hypothesis of acoustic coordination where individuals could inform their conspecifics about an increase in the immediate predation risk through appropriate alarm calls and trigger an escape response of the group if needed.

Seagrass beds are ecologically and economically important coastal ecosystems, and seagrass-associated organisms are a key part of their biodiversity. Marine organisms that reproduce through broadcast spawning are likely to have less genetic differentiation among populations than those that use other modes of reproduction, but this has not been well studied. Here, we investigated the genetic diversity, genetic differentiation, and migration patterns of the seagrass-associated sea star Protoreaster nodosus across 12 sites spanning approximately 2500 km from the Ryukyu Archipelago, Japan, to the Philippines. We genotyped 405 individuals by using seven microsatellite loci and analyzed allelic richness and expected heterozygosity as indices of genetic diversity. Of these two indices, only expected heterozygosity decreased slightly with increasing latitude. These results suggest that genetic diversity has not clearly decreased, even in the isolated Ryukyu Archipelago populations. Geographic distance was significantly correlated with genetic differentiation (pairwise F_ST: − 0.005 to 0.049). However, populations in the Ryukyu Archipelago and the Philippines showed relatively low genetic structuring and the pairwise genetic differentiation between these regions was often non-significant. Analysis of historical migration rates showed bidirectional north–south migration, which appears to be influenced by the Kuroshio Current and its countercurrents.

Classification of cryptic species is important for assessing biodiversity and conducting ecological studies. However, morphological classification methods face the loss of morphological information due to subjectivity in geometric morphometrics, while an incomplete database and horizontal gene transfer limit the molecular approach. A novel approach combining 3D modeling and artificial intelligence algorithms using morphological and molecular data was developed for species classification. Cryptic species from the Vignadula genus were used to test the feasibility of this new approach. Molecular identification results as data labels were used for training models, and for validating classification results of machine learning and deep learning. Our approach achieved accuracies of over 80% in distinguishing between V. atrata and V. mangle, which were identified by molecular data along China’s coast. The result of the confusion matrix indicated the misidentified individuals were due to the morphological similarity in the intermediate zone. The feature importance analysis highlighted the significant contribution of average curvature—a 3D feature—to the task, indicating the feasibility of the 3D model in cryptic species classification. Utilizing 3D models and artificial intelligence, this study presents a novel approach for classifying cryptic species of molluscs.

Knowledge of the diet of marine predators such as seabirds is fundamental to understanding the ecological cascades they may influence and the impact that environmental changes may have on them. Diet analysis of seabirds frequently relies on the identification of fish otoliths in pellets. However, it is recognised that the true dietary importance of fish with small and fragile otoliths is likely underestimated, requiring an additional method. In this study, we compared the identification of otoliths with that of vertebrae in pellets to gain a more complete picture of seabird diet. We identified fish otoliths and vertebrae from 2584 great skua Stercorarius skua pellets collected between 2014 and 2017 from five colonies in Scotland. Diet varied markedly between colonies, comprising mostly fish in Shetland and mostly birds in St Kilda. 10% of pellets contained otoliths compared to 70% with fish vertebrae. Atlantic herring Clupea harengus and Atlantic mackerel Scomber scombrus were the most common fish species at all colonies when using vertebrae in contrast to being virtually absent when using otoliths. Conversely, the occurrence of Norway pout Trisopterus esmarkii and pollock Pollachius pollachius otoliths was six and eight times, respectively, higher than for vertebrae. Therefore, combining data from both otoliths and vertebrae provides a more complete profile of the fish component of seabird diet. This is fundamental to improving our understanding of the impacts of marine management policies on seabirds, as well as how changes in the population size of such seabird species might affect their prey species.

Estuaries are crucial feeding, nursery and resting sites for fish but can also be subject to the impacts of severe flooding. The environmental features of estuaries can mediate how they respond to these impacts. For example, the size, configuration, and context of estuarine habitats across seascapes affects the value of patches for fish, and so fish assemblages at sites with a greater habitat extent or closer to the mouth of an estuary may rebound more quickly from flooding. We investigated how a once in 100-year flood event affected fish assemblages at approximately 600 sites across 13 estuaries and six estuarine habitats (bare sediments, log snags, mangrove forests, rocky structures, saltmarsh and seagrass meadows) in southeast Queensland, Australia, and determined whether flood impacts were mediated by the position of sites within the broader estuarine seascape. Sites were surveyed annually in 2020/2021 (pre-flood) and 2022 (6 months post-flood) using underwater videography. Flooding modified the structure of the fish community and reduced the abundance of fish targeted by local fisheries in all six habitats. Crucially, flood effects on fish were greater at sites near more expansive urbanisation in some ecosystems, but lower at sites nearer to the estuary mouth. Maximising the extent of natural habitats across estuaries can mediate the effects of floods and should be priorities for restoration and management plans seeking to maintain biodiversity and fisheries productivity in the face of increasing climate-related disturbances.

Understanding the impact of environmental and biological factors on species’ habitat use is crucial for conservation. A regular presence of common bottlenose dolphins (Tursiops truncatus) has recently been observed in the Western Ligurian Sea, but their distribution, habitat preferences, and social dynamics remain poorly understood. This study aims to investigate these aspects, focusing on spatial distribution and habitat partitioning by age classes. Data were collected during 273 boat-based surveys from April 2018 to December 2021, resulting in 146 dolphin sightings. Group size and composition were analysed based on three group-types: N-groups including at least one newborn (n = 35), C-groups with at least one calf but no newborns (n = 62) and A-groups comprising only independent juveniles, subadults and/or adults (n = 49). Using an ensemble modelling approach (BIOMOD), each group’s distribution was separately modelled incorporating seven environmental variables. Bathymetry, distance to the shelf break, bottom type and sea surface temperature emerged as the most significant predictors influencing groups’ distribution. Results showed N-groups predominantly occupying areas further from the shore, C-groups distributed across both coastal waters and areas near the shelf break and A-groups principally found very close to shore. The study suggests habitat selection and group size vary based on the unique needs and threats faced by the different age classes. These insights are highly valuable for managing bottlenose dolphins in the Ligurian Sea, considering the area’s particular morphology that leads to an important overlap between their presence and local anthropogenic activities.