Marine Biology最新文献

In aquatic environments, low dissolved oxygen concentrations can result in depressed bivalve defense systems while promoting anaerobic bacterial growth, ultimately leading to increased bivalve mortality rates. Although the relationship between low oxygen availability and bivalve mortality has been previously examined, the mechanisms of mortality remain not well understood, limiting our ability to predict mass mortality events. In this study, the effect of anoxia (< 0.1 mgO₂L^-1) on adult oyster (Crassostrea virginica) mortality rates was explored experimentally using a factorial design, which included the effect of temperature (20°C vs. 28°C) combined with the presence/absence of an exogenous bacterial source (anoxic sediment vs. sterile sediment). Additionally, the effect on oyster mortality rate of removing vs. not removing deceased oysters from the experimental chambers was assessed. Oyster mortality rates, estimated as the time taken for half of the population to die (LT₅₀) in anoxic conditions were significantly affected by temperature, the presence of anoxic sediment, and experimental execution (removing vs. not removing deceased oysters). Temperature had the greatest effect on mortality overall, with high temperatures resulting in increased mortality rates, whereas the presence of anoxic sediment only increased mortality rates consistently at high temperatures. The results of this study suggest that bacterial sources play a role in the mortality rate of oysters under warm anoxic conditions.

Supplementary information: The online version contains supplementary material available at 10.1007/s00227-025-04617-4.

Antarctic krill, Euphausia superba (Dana i Am J Sci Arts Ser 2(9):129-133, 1850), are both central ecosystem components in the Southern Ocean, and the target of a growing commercial fishery. Understanding the trophic interactions which shape krill population dynamics is essential to sustainably managing human impacts on this key species. While the roles of krill as grazers of phytoplankton and as prey for vertebrate predators are relatively well understood, very little is known about interactions with their smallest predators- the parasites. We investigated the assemblage of parasites present in E. superba, and the impacts of parasites on krill somatic growth. We found 15 distinct parasite types across a sample of 100 krill, including seven types of Gregarine Apicomplexa, two types of internally infecting ciliates, three types of epibiotic ciliates, fungi, syndiniales, and a Parorchites zederi cestode worm. Apicomplexa and epibiotic ciliate infections were linked with lower growth rates, with these two parasites explaining 10% and 24% of the observed variation in krill growth, respectively. Although much uncertainty remains, scaling these results to the population level suggests parasites may be responsible for as much reduction in krill biomass annually as vertebrate predators, indicating the importance of considering these trophic links in food web modelling and ecosystem-based management.

Supplementary information: The online version contains supplementary material available at 10.1007/s00227-025-04673-w.

The polar sea-ice zones are highly productive and seasonal habitats that support large populations of vertebrate predators. In the Antarctic, snow petrels (Pagodroma nivea) are regarded as highly ice-dependant, yet knowledge of their habitat use and foraging distribution during the breeding period comes largely from ship-based observations. Snow petrels show sexual size dimorphism, and previous studies have demonstrated a degree of sexual segregation in habitat use in East Antarctica during the incubation period. Here, we characterise the movements, behaviour and habitat use of foraging snow petrels using bird movement and remotely sensed environmental data. We tracked snow petrels from two colonies in Dronning Maud Land, East Antarctica during early chick rearing in January to February 2022, a period of unusually rapid sea-ice retreat in the region. During the chick-rearing period, mean foraging range was c. 395 km and did not differ between the sexes. However, we found some evidence of differing habitat use between the sexes: males foraged more in areas of higher sea-ice concentration and over the continental shelf, while females utilized deeper waters and lower sea-ice concentrations. Sexes also diverged in their behavioural responses to both sea ice and depths, with males more likely to switch to foraging in areas of higher sea-ice concentrations than females and females more likely to switch to foraging in deeper waters than males. Although both sexes were more likely to forage at higher sea-ice concentrations, they also used areas with little or no sea ice. This contrasts with previous studies and may have been due to the unusual paucity of sea-ice cover during our tracking period.

Supplementary information: The online version contains supplementary material available at 10.1007/s00227-025-04657-w.

Devil rays (Mobula spp.) are caught in fisheries across the Indian Ocean, with reports of significant recent declines in catch and sightings. Globally, the few populations studied have extremely low population growth rates due to low fecundity and long reproductive cycles, making them highly vulnerable to overfishing. To allow for assessment of the current sustainability of devil ray catch in the Indian Ocean, we provide estimates of age using the caudal vertebrae; somatic growth using a Bayesian, multi-model approach; maximum intrinsic rate of population increase (r _max ); and fishing mortality for Endangered Spinetail Devil Ray (Mobula mobular) and Bentfin Devil Ray (M. thurstoni) sampled from small-scale fisheries catch in Indonesia, Kenya, and Pakistan. The oldest individuals of Spinetail Devil Ray (n = 79) and Bentfin Devil Ray (n = 59) were 17.5 and six years, respectively. Both species had relatively low growth coefficients (k = 0.05 and g = 0.19 year^-1, respectively), with the von Bertalanffy and logistic models providing the best fitting growth models, and low r _max (0.109 and 0.107 year^-1, respectively) indicating that they are highly sensitive to overexploitation. Fishing mortality F estimates (0.16 and 0.18 year^-1, respectively) were higher than r _max and exploitation ratio E (0.77 and 0.80, respectively) were higher than an optimum value of 0.5 for biological sustainability for both species, suggesting that the fisheries catches of the species are unsustainable. We demonstrate an approach to assess data-poor species and apply this to two Indian Ocean devil ray species. The results highlight the urgent need for better management actions to reduce the catch of all devil rays to prevent species extinction and aid in population recovery.

Supplementary information: The online version contains supplementary material available at 10.1007/s00227-024-04564-6.

Group living is widespread and beneficial to metazoans. It improves protection and survival opportunities, reinforcing interspecific competitiveness. Benthic cnidarians often colonize large surfaces. Evidence of collective capture and exploitation of large prey by small, clumped polyps suggests that aggregation is functional to access food resources hardly achievable by isolated individuals. In turn, the chance to catch large prey may represents a driver of aggregation in polyps, whether beneficial to their fitness. Here, the effects of group foraging on aggregation, asexual reproduction, and growth rates of Aurelia coerulea von Lendenfeld 1884 polyps were experimentally tested by providing them with either small or large prey, or a mix of both to simulate the co-occurrence of preys at sea. As expected, some polyps were not able to reach the large prey. Hence, the population was a posteriori divided into group-foragers and solitary-feeders. In general, the large prey diet resulted in higher population fitness and when simultaneously supplied with the small prey represented an energetic booster resulting beneficial for all group-members. The decrease of interindividual distances was reported among group-foragers, that converged towards each other. Cnidarians are basal in metazoan evolution, and the comprehension of their collective foraging behavior, as well as the processes leading to the selective feature driving them to forage in group or not, may be essential to better understand the evolution and spread of social foraging in animals. Moreover, the access to large prey by sessile polyps of Aurelia coerulea could be pivotal in determining the increase in abundance of adult bloom-forming medusae.

Museum specimens preserve genetic information that can help resolve phylogenetic relationships of now extinct species. The Caribbean monk seal, Neomonachus tropicalis, is the only marine mammal driven to extinction in tropical seas and one of the few marine mammals to go extinct in historical times. Prior to 1700 it was widely distributed throughout the coasts of North, Central and South America, and in the Bahamas, Greater and Lesser Antilles. The species was first taxonomically placed in the genus Monachus, along with the Hawaiian and Mediterranean monk seals and it was later moved together with the Hawaiian monk seal into the newly described genus Neomonachus. Here, we present the complete mitochondrial genome of the Caribbean monk seal and a phylogenetic reconstruction, confirming its sister taxa relationship with the Hawaiian monk seal, and thus the monophyly of the genus Neomonachus. Our estimates of divergence times are contemporaneous with or predate the emergence of the Isthmus of Panama. We also identify limited genetic variation among five specimens of Caribbean monk seal.

Predation is a key process that influences the structure and functioning of ecosystems. Tethering experiments, which involve restraining prey or prey analogs in field settings, are used to evaluate predation with minimal manipulation of predators and the environment. However, tethering experiments alter the behavior of mobile prey, an issue that increases in severity with prey mobility and reliance on that mobility to evade predators, resulting in artifacts that complicate the interpretation of experimental findings. Given their widespread and rapidly evolving use, we review and reconsider the applications of tethering experiments in marine ecosystems, their utility in measuring predation, associated artifacts, theoretical, methodological, and statistical considerations and challenges, and how to overcome these. Breaking down the predation process into its successive stages (encounter, attack, capture, and consumption), we consider that tethering experiments effectively measure two major aspects of predation: (1) relative predation rates (requiring all four stages, and resulting in successful predation) and (2) predation risk (requiring only encounter and attack). We suggest that tethering experiments be designed to test hypotheses that target particular stages or all stages of the predation process and its drivers, through manipulating tethering experimental designs, conducting direct observations of tethering experiments, collecting additional community or environmental data, combining tethering with other experimental approaches, and through statistical analyses. This general approach facilitates both our understanding of the limitations and utility of tethering experiments to compare patterns and identify drivers of predation rates and risk in the field, topics of study that remain underrepresented in the literature.

Climate change may impact individual organisms in different ways, a consideration often overshadowed by predominant focus on population effects in studies. We examined three estuarine fish species to determine if individual fish performance, persisted across winter water temperatures. Fish performance at 16 °C (current Sydney winter estuarine water temperature) and 20 °C (predicted under climate change) with low and high food regimes was assessed using key physiological (growth, aerobic scope, burst speed) and behavioural parameters (foraging activity, boldness, shelter usage, predator escape response). We expected a strong positive relationship between performance at 16 °C and 20 °C for each parameter, and interactions with food level, however in general this was not found for any species. Relative performance was only maintained across temperatures for a few parameters, such as bite rate, boldness, and shelter response in one species (trumpeter Pelates sexlineatus), with aerobic scope in silver biddy Gerres subfasciatus, and boldness in fortescue Centropogon australis. Our results suggest that individuals’ fitness (directly via changes in growth, indirectly via behaviours) might be impacted by climate warming due to differences in relative performance among juvenile individuals across water temperatures. Changes in relative performance among individuals may initially compensate for a population-level response, thereby buffering the effects of climate change.

Marine Heat Waves (MHWs) occurrence has been increasing in the Mediterranean Sea. The effects of field simulated MHWs of different intensity (medium and high temperature) on the transcriptome expression of the endemic seagrass Posidonia oceanica were evaluated considering different origins of the plant. The aim of the study was reached through a common garden transplant experiment in the North-west of Sardinia (Italy), where two P. oceanica meadows characterized by different thermal regimes (cold and warm) were chosen. MHWs were simulated in front of a power plant, that creates a natural laboratory by releasing warm water in the sea. Differential gene expression and GO enrichment analyses highlighted differences in the transcriptomic profiles of plants from cold and warm environments suggesting that the MHWs induced different levels of stress due to different tolerance to the heat event. Plants from both origins activated processes to achieve protein homeostasis, but only cold plants activated an antioxidant defense and altered sugar metabolism, both indicators of heat stress. Within plants of the same origin, a different response to MHW intensity was also detected: while warm plants showed the most complex response at high temperature rather than at medium temperature, cold plants seemed to better cope with the medium temperature intensity rather than with high temperature.

The nature of symbiotic relationships between organisms can be difficult to assess and may range from commensalism, to mutualism, and parasitism. Trophic linkage and feeding ecology are essential to disentangle symbiont-host relationships/interactions. Amphipods of the genus Dactylopleustes are known as urchin symbionts. Though their ecology remains largely unknown, Dactylopleustes was recently reported to aggregate on diseased hosts, suggesting that Dactylopleustes feeds on diseased urchins’ tissues and uses urchins as both a habitat and prey. We investigated by DNA metabarcoding analyses, the feeding ecology of Dactylopleustes yoshimurai in relation to growth and disease status of the host (Strongylocentrotus intermedius). Contrary to our hypothesis, sequence reads from the gut contents were dominated by planktonic copepods regardless of body size or host disease status. These results suggest that they mainly feed on copepod fecal pellets deposited on sediments, and do not have a strong trophic linkage with their host. Large individuals on diseased urchins feed more on urchins than those on healthy urchins. However, their main prey still remains copepods, implying that host disease has a limited effect on the feeding behavior. In conclusion, our study indicates that this species is mainly commensal, but also may parasitize its host depending on the situation.