Marine Biology最新文献

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.

Intertidal animals deal with physical gradients daily that create stressful conditions across the shore. These physical gradients influence the physiological performance of organisms, requiring responses that may differ with height on the shore. We examined the respiratory response to aerial exposure in the invasive Asian shore crab Hemigrapsus sanguineus during periods of low tide emersion using two field experiments. The first experiment simultaneously measured respiration of individuals collected from different heights on the shore, which had therefore been emersed for different lengths of time. The second experiment measured respiration of individuals collected at different times from the same tidal height. Respiration rates of crabs in both experiments increased immediately after emersion, nearly doubling by and peaking at ~ 1.5 h of aerial exposure, before decreasing again over the next 1.5 h. These results suggest that the energetic cost of low tide exposure is greatest shortly after emersion during the first half of the typical low tide period, but then decreases thereafter. These respiration patterns facilitate the broad intertidal distribution of this species on rocky shores throughout its range.

Animals have a deep evolutionary relationship with microbial symbionts, such that individual microbes or an entire microbial community can diverge alongside the host. Here, we explore these host-microbe relationships in Echinometra, a sea urchin genus that speciated with the Isthmus of Panama and throughout the Indo-West Pacific. We find that the eggs from five Echinometra species generally associate with a species-specific bacterial community and that the relatedness of these communities is largely congruent with host phylogeny. Microbiome divergence per million years was higher in more recent speciation events than in older ones. We, however, did not find any bacterial groups that displayed co-phylogeny with Echinometra. Together, these findings suggest that the evolutionary relationship between Echinometra and their microbiota operates at the community level. We find no evidence suggesting that the associated microbiota is the evolutionary driver of Echinometra speciation. Instead, divergence between Echinometra and their microbiota is likely the byproduct of ecological, geographic, and reproductive isolations.

The grazing impacts of two Acartia species (Acartia omorii and A. steueri) on size-fractionated phytoplankton biomass were measured in Jangmok Bay, Korea (34°59′37.8" N, 128°40′28.2'' E) from January to May 2015. Total chlorophyll (Chl-a) concentrations ranged from 0.66 to 5.18 µg L⁻¹, and micro-phytoplankton (> 20 µm) comprised up to 66% (range, 10.5–65.6%) of the total pigment. The total abundance of Acartia species ranged from 267 to 5931 ind. m⁻³, and these copepods accounted for 20.8 to 88.0% of the total copepod abundance. The ingestion rates of A. steueri (r² = 0.904, P = 0.013) and A. omorii (r² = 0.239, P = 0.046) showed a high correlation with micro-phytoplankton. The average grazing impact of Acartia species on phytoplankton biomass was approximately 6.8 ± 11.8% (range, 0.1–69.0%). Temperature–salinity (T–S) diagram analysis revealed distinct environmental preferences for each species; A. omorii preferred a broader temperature range of 6.2 to 17.1 °C and a salinity range of 31.8 to 33.5, whereas A. steueri was more restricted, preferring temperatures between 6.5 and 12.8 °C and a salinity range of 32.2 to 33.5. These findings not only contribute to our understanding of the ecological roles of these copepod species in marine ecosystems but also highlight the importance of continuous research regarding the mechanisms driving their coexistence and interaction with the coastal food web.

The ecological importance of rhodolith beds stems from their role as structurally complex three-dimensional habitat formed by free-living red calcareous algae. Their structural singularity is due to the great variety of complex and branching morphologies exhibited by rhodoliths that create interstitial spaces and increase their surface area. This increases the ecological niches for cryptofauna and provide refuge for a high number of organisms, which is why rhodolith beds are considered biodiversity hotspots. In this work, we studied a rhodolith bed located in the Menorca Channel, formed by several species of red calcareous algae that exhibit a great variety of morphologies and form an extensive and heterogeneous habitat. This study explored the morphological diversity of the rhodolith bed, comparing the ‘Core Habitat’ (within the center of the bed with the highest densities of rhodoliths) with the boundaries or ‘Adjacent Habitat’ where rhodolith density was lower. Our results show that all rhodolith growth forms (branched, pralines and boxwork) in the Core Habitat had higher interstitial space and were larger than the ones from adjacent zones. Moreover, we explored the three-dimensional techniques to study the morphological characteristics that have historically been studied in two dimensions. This study contributes to the knowledge of morphological diversity in well-preserved rhodolith beds from continental shelves in the western Mediterranean Sea and reinforces the use of three-dimensional measurements, specifically the interstitial space of branched rhodoliths, to provide more accurate data on habitat complexity.

Many dinoflagellate species are bioluminescent, which is one of the anti-predation mechanisms in these species. In addition, dinoflagellate species experience a wide range of salinities in the ocean. However, the effects of salinity on their bioluminescence intensity has only been investigated for one species. Here, we explored the effect of salinity on the bioluminescence intensity of the heterotrophic dinoflagellate Noctiluca scintillans NSDJ2010 feeding on the chlorophyte Dunaliella salina, the heterotrophic dinoflagellate Polykrikos kofoidii PKJH1607 feeding on the dinoflagellate Alexadrium minutum, and the autotrophic dinoflagellate Alexandrium mediterraneum AMYS1807. Moreover, to determine the cell volume and growth effects on bioluminescence intensity, the cell volume and growth rate of three bioluminescent dinoflagellates were simultaneously investigated. The mean 200-s-integrated bioluminescence intensity (BL) per cell, equivalent to the total bioluminescence, of N. scintillans, P. kofoidii, and A. mediterraneum was significantly affected by salinity and increased with increasing salinity from 10 to 40. The results of the present study suggest that the total bioluminescence of N. scintillans, P. kofoidii, and A. mediterraneum in offshore and oceanic waters is greater than that in estuarine waters.

Comprehending how environmental variability shapes foraging behaviour across habitats is key to unlocking insights into consumer ecology. Seabirds breeding at high latitudes are exemplars of how marine consumers can adapt their behaviours to make use of predictable foraging opportunities, but prey tends to be less predictable in tropical oceanic ecosystems and may require alternative foraging behaviours. Here we used GPS and time-depth recorder loggers to investigate the foraging behaviour of central placed adult red-footed boobies (Sula sula rubripes), a tropical seabird that forages in oceanic waters via diving, or by capturing aerial prey such as flying fish in flight. Dive bout dynamics revealed that red-footed boobies appeared to exploit denser, but more sparsely distributed prey patches when diving further from the colony. Furthermore, although we found no evidence of environmentally driven habitat selection along their foraging routes, red-footed boobies preferentially dived in areas with higher sea surface temperatures and chlorophyll-a concentrations compared to conditions along their foraging tracks. This multi-scale variation implies that habitat selection differs between foraging routes compared to dive locations. Finally, red-footed booby dives were deepest during the middle of the day when light penetration was greatest. Ultimately, we highlight the importance of gaining insights into consumer foraging across different ecosystems, thereby broadening understanding of how animals might respond to changing environmental conditions.