Marine Biology最新文献

Speciation processes in the marine environment are often directly associated with vicariant events. In the case of loliginid squids (Cephalopoda: Loliginidae), these processes have been increasingly elucidated in recent years with the development of molecular technologies and increased sampling in poorly studied geographical regions, revealing a high incidence of cryptic speciation. Doryteuthis pealeii is a commercially important squid species for North Atlantic fisheries and has the second broadest geographic distribution in this genus. This study aimed to investigate the evolutionary history of this species and which biogeographic events may have influenced its diversification by assessing mitochondrial and nuclear markers. Our findings indicate that two previously detected lineages diverged from one another ~ 8 million years, compatible with the formation of the Caribbean and the establishment of the Amazon plume. Furthermore, separation between a North Atlantic and a Gulf of Mexico lineage during the Pleistocene period was noted. The inadequate classification of this cryptic diversity may have negative implications for the development of effective conservation and fisheries measures.

Polar ecosystems are subjected to many stressors, including climate change, that impact their overall functioning. Seabirds are good bioindicators of these systems as they readily respond to changes in environmental conditions. To quantify how environmental changes affect their life history, data on seabird diet, spatial distribution and body condition are needed to reveal the underlying mechanisms. We explored possible drivers of the winter distribution of single-colony populations of Atlantic puffins Fratercula arctica and black-legged kittiwakes Rissa tridactyla, two of the most numerous seabird species in the North Atlantic. Based on carbon and nitrogen stable isotopic data from feathers moulted during winter migration, we identified three groups of Atlantic puffins and two groups of black-legged kittiwakes occupying different isotopic niches. We then used geolocator tracking data for the same birds to determine if these groups reflected parallel differences in the location of moulting grounds rather than differences in their diet. We found that the isotopic niches of the three Atlantic puffin groups likely resulted from their use of different habitats during winter moult. In contrast, the isotopic niches of the two black-legged kittiwake groups were more likely a result of differences in their diet, as both groups were distributed in the same area. These findings suggest that different winter feeding and/or migration strategies may play a role in shaping the body condition of individuals for their following breeding season. We discuss the role of environmental conditions encountered by seabirds during winter migration to further elucidate such intracolony divergence in strategies. As polar ecosystems experience rapid changes in environmental conditions, the approach presented here may provide valuable information for the development of effective conservation measures (taking both intra- and intercolony variability into account), and to better predict future impacts of climate change.

Abstract

Green sea turtles (Chelonia mydas) face many threats from anthropogenic activity and are listed as Endangered on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. They spend the majority of their lives in coastal foraging areas, and show strong fidelity to narrow foraging ranges. Understanding the foraging ecology of green turtles is therefore important for their management and conservation. Using stable isotopes analysis (n = 200) and identification of stomach contents (n = 21), this study investigated the foraging ecology of four distinct green turtle foraging aggregations (Goro, Isle of Pines, Ouen Island and Uo/Mato Islands) within the Grand Lagon Sud. This World Heritage Area located in New Caledonia supports regionally important nesting and foraging green turtle populations. The δ¹³C and δ¹⁵N values of skin samples ranged from − 19.3 to − 7.3‰ and 2.8–15.9‰, respectively. Metrics of isotopic niche and regression analyses were used to assess the degree of omnivory, trophic diversity and potential ontogenetic diet shifts in the different aggregations of foraging green turtles in this location. Each of the four sites and four age-classes had distinct isotopic niches, with evidence of omnivory and ontogenetic shifts, particular in new recruits and juveniles, and at Goro and Uo/Mato Islands. This was generally supported by the stomach contents analyses of a small number of green turtles opportunistically sampled from traditional ceremonies. This study provides important information on the foraging ecology of green turtles in New Caledonia, supporting management outcomes in this region. This collaboration with the tribes of the Grand Lagon Sud is also the first step towards the integrated management of the resource.

The giant kelp Macrocystis pyrifera is in global decline as a result of numerous stressors operating on both local and global scales. It is a species that holds significant value in terms of the ecosystem services that it provides and its application in aquaculture. In order to safeguard, restore and utilize this species, it is essential that a sound understanding of genetic structure and diversity is established at scales relevant to local management. Seven microsatellite markers were used to analyze 389 individuals from sites across eight geographical regions in New Zealand. While samples of M. pyrifera from the west coast of the South Island (Fiordland), were genetically isolated, the biogeographic separation of sites along the east coast of New Zealand, between Wellington and Stewart Island, remained unclear due to low genetic differentiation between regions. The greatest genetic diversity was seen in the southeast sites, whereas the northeast had the lowest diversity. This pattern is likely driven by the effects of stressors such as high sea surface temperature in these areas as well as oceanic circulation patterns. A key finding from this work was the significant genetic isolation, and therefore vulnerability of M. pyrifera in the Fiordland population, an area that is being subjected to more intense and longer lasting heatwave events.

Abstract

Microplastic ingestion by marine fishes has been of particular interest, as many species are the target of commercial fisheries and, thus, have a strong connection with human health. Consumption of microplastic thru seafood is likely to have harmful effects on people globally but mainly on social groups that highly depend on fisheries for self-consumption. Here, we first aim to characterize the presence of microplastics in species targeted by small-scale fishers; and explore if the fish consumption of microplastic particles is associated with biological factors. Second, we applied semi-structured interviews to small-scale fishers to investigate, from a socio-environmental perspective, the potential social and environmental impacts of contamination by microplastics on the local communities. We found that commercially important fish families regularly contained microplastics in their tissues, and the consumption of microplastics by fish caught through traditional fishing gear depends on traits such as species mobility but the microplastic load also depended on the type of fishing gear used. Species with a wide home range had a higher load of microplastics than fish with a small home range but also seemed to be related to the fishing method. The observed differences in microplastic content on target species are likely to be transferred to humans in a non-random fashion. This work implies that microplastic pollution in commercial fish might represent an environmental and social issue that is not well understood by the fishing community in the Mexican Caribbean, with potential ramifications for marine resource management.

Investigator disturbance while monitoring seabirds can result in lower survival rates and breeding success, leaving lasting negative impacts on the population and biasing observations. For example, monitoring rhinoceros auklets (Cerorhinca monocerata) and other burrowing alcids can reduce breeding success or even survival through handling stress and damage to nesting habitat. For this reason, researchers must seek to decrease colony disturbance. Automated radio-frequency identification (RFID) via passive integrated transponder (PIT) tags is an inexpensive and reliable way to identify individual presence and record attendance behaviour, avoiding the need to recapture seabirds or visit the colony frequently. PIT tags either can be implanted subcutaneously or attached externally to leg bands, but it is unclear which method causes lower disturbance. To examine the impact of PIT tagging on rhinoceros auklets nesting in artificial burrows on Middleton Island, Alaska, we monitored burrow entrances with automated recording RFID readers to collect presence and nest attendance data. PIT-tagged (either band attachment or subcutaneous implant) and control birds had similar breeding success and chick growth rates. Breeding success was similar between nests with one or two parents marked. Birds tagged externally were detected less often than birds marked with a subcutaneous implant. We conclude that PIT tagging of rhinoceros auklets is a relatively non-invasive method for seabird monitoring, and that subcutaneous implants do not cause more disturbance than external attachment.

Biological invasions have modified habitat structure, forcing changes in ecosystem functions. Structural complexity modulates diversity and trophic pathways, but the roles of invasive species in mediating coral reef habitat attributes and trophic effects are poorly understood. We investigated the influence of invasive corals on reef structural complexity and their implications on reef fish trophic structure. To assess habitat complexity and trophic relationships, we used a digital probe to map reef rugosity and characterized benthic cover and fish abundances by video and visual estimates. We calculated a coral skeleton complexity index (for individual invasive and native colonies) by building high-resolution three-dimensional models with photogrammetry techniques. The study was conducted between February 2018 and March 2019 in Cascos Reef, located on the east coast of Brazil. We reveal that the complex morphology of the invasive coral Tubastraea spp. skeleton had a significant positive effect on reef rugosity, contributing to substrate complexity at a sub-metric scale. However, this likely did not promote reef fish diversity but altered the assemblage structure patterns, demonstrated by a negative relationship between coral colony complexity index and abundance of trophic groups such as roving herbivores and omnivores and a positive relationship with planktivores. Thus, our findings support that habitat attribute modification promoted by invasive corals can influence the benthos-fish dynamic, promoting some fish groups to the detriment of others, with pervasive implications for ecosystem functions. Global changes are increasing invasions worldwide, enhancing the need for effective policies for regulation and management to ensure human well-being and ecosystem services.

For anadromous fish entering the marine environment, we expect the probability of avoiding predation and starvation to increase with the quality and/or quantity of dietary resources consumed during the period immediately prior to, and following, ocean entry. Here, we report the results of research examining trophic history in relation to fork length, mass, and body condition in juvenile Chinook salmon captured in the southern Bering Sea using δ¹³C and δ¹⁵N analysis of skeletal muscle and liver samples. Our results show little inter-individual variability in δ¹⁵N, but variability in δ¹³C among tissues and within and among years was observed. Further, we found few relationships between δ¹⁵N and morphological or condition metrics, but strong relationships between δ¹³C and fork length, body mass, and Fulton’s K. We attribute the similarity in δ¹⁵N among individuals to high trophic level feeding (i.e., piscivory) associated with the prolonged duration of freshwater residency observed for juvenile Chinook salmon in our study area. Variation in δ¹³C, as well as relationships between δ¹³C, fork length, body mass, and Fulton’s K can be attributed to variability in carbon sourcing resulting from the large spatial footprint of our study area. In addition to relating these findings to Chinook salmon ecology, we offer guidance for future use of δ¹³C and δ¹⁵N analysis in studying early marine trophic interactions in anadromous fish.

Abstract

Understanding metabolic and immune functional genes in the gut microbiota of sentinel species, such as spotted seals (Phoca largha), is essential for assessing the health of marine mammals and improving conservation strategies. Information on the gut microbiome is essential for improving conditions in captive species thus aiding in pinniped population restoration, however, it remains poorly understood. In this study, the microbiota in feces from wild and captive P. largha obtained from Liaodong Bay and an aquarium in China were analyzed using metagenomic sequencing. The results showed significant differences in the diversity, composition, and function of gut microbiota between wild and captive P. largha. The bacteria responsible for rapid absorption of energy to product body fat, Firmicutes, were more abundant in the gut microbiota of wild P. largha than in captives. Stronger biosynthesis abilities of nutrients and innate immune factors were observed in the gut microbiota of wild P. largha compared to captive samples. Regarding biomolecules (volatile fatty acids, amino acids vitamins, and several innate immune factors), only the biosynthesis of vitamin B1, secondary bile acids, and a few amino acids were significantly higher in the gut microbiota of the captive P. largha. E. coli, and genera of Bradyrhizobium, Bacteroides, and Rhodanobacter were the dominant biosynthesis functional bacteria in wild P. largha. Overall, these findings showed that wild P. largha had better health status compared to captive species; more importantly, they provide critical data for the development of effective strategies to enhance the growth and health of pinnipeds in captive environments.

Artificial reefs are used as tools for the restoration of degrading coral reefs by providing new settlement substrates. The initial recruitment process consists of the formation of microbial biofilms shortly after deployment. The aim of the present study is to compare biofilm composition and development on artificial substrates at two different coral-reef sites. These locations differ in their environmental conditions, including their level of anthropogenic impact. Substrate and seawater samples were collected four times during the first 6 months after deployment, using a new methodology termed ‘tab-by-tab’. DNA was extracted, sequenced, and sorted for both prokaryotic (16s) and eukaryotic (18s) genes. No difference was found between the planktonic communities in the water, yet significant differences were observed in the biofilm communities on the structures at the two sites. Moreover, differences were recorded in coral recruitment rates, which are known to be affected by biofilm composition. Our findings suggest a potential role of environmental conditions in the early biofilm stages (first few months), which in turn may impact the succession and development of coral-reef communities and the success of artificial reefs as restoration tools.