Journal of Sea Research最新文献

Dispersal, a critical factor in the viability of marine organisms, is strongly influenced by the physical dynamics of the ocean. Fronts, as a common phenomenon in ocean dynamics, can theoretically impact the dispersal of organisms and ultimately cause spatial homogeneity or heterogeneity of marine communities. However, there is relatively limited understanding concerning whether frontal formation hinders the connectivity between communities and thus results in differences in community structure. To verify whether the formation of fronts caused differences between communities, 60 eDNA samples and their environmental parameters were collected from 32 sites in the Yangtze River estuary and its adjacent area, and four groups, the Yangtze River front-inner group (YRI), the Yangtze River front-outer group (YRO), the Zhejiang costa front-inner group (ZCI), and the Zhejiang coast front-outer group (ZCO), were compared to examine the differences in fish communities between the sides of the front. The results showed that there was a significant difference between YRI and YRO, suggesting that the front affected the community structure. There was no significant difference in fish communities between ZCI and ZCO, indicating that fronts could only hinder dispersal at high intensities. The difference between YRI and YRO possibly resulted from dramatic changes in temperature, salinity, and turbidity related to the front. Fronts also separated water masses with different environmental characteristics and thereby attracted fish to their optimal habitats. Overall, fronts appear to be ecologically significant for fish dispersal and community differentiation.

While many studies have analyzed the diet of marine consumers using traditional morphology-based methods, the integral diet of many species of functionally important groups such as benthic invertebrates remains poorly resolved. This hinders our ability to precisely establish trophic links among species, which is necessary to understand food webs and ecosystem dynamics. Here, we applied DNA metabarcoding to obtain a high resolution picture of the animal fraction of the diet of six species of crustaceans in the Bay of Biscay; the edible crab Cancer pagurus, the velvet crab Necora puber, the circular crab Atelecyclus undecimdentatus, the spider crab Maja brachydactyla, the shrimp Crangon crangon, and the hermit crab Pagurus bernhardus. We used two pairs of primers targeting the 18S rDNA (generalist) and 12S rDNA (fish-specific) regions to identify prey that makes up the animal fraction of the diet. Based on occurrence data, 54 prey taxa belonging to 5 different phylum mostly represented by teleost fishes and malacostracans were identified. Through a high-level of prey detection, results indicate a scavenging strategy across all consumers mostly based on the consumption of preys likely originating from fishing discards. This study also reveals patterns of niche overlaps among consumers differentiating C. crangon from others and suggesting high overlap in animal resource use between N. puber and M. brachydactyla as well as C. pagurus. High resolution diet description revealed the complexity of trophic interactions on a local scale.

Site elevation is a crucial driver for mangrove restoration, and litter production restoration is a significantly important target of mangrove restoration, but little attention has been paid to impact of site elevation on the production and elemental composition of litter in the restored mangrove forests. This study compared the production and elemental composition of mangrove litter at the three intertidal elevations, to explore impacts of site elevation on the production and elemental composition of mangrove litter. Compared with the upper elevation site, significantly lower annual litter production was found at the lower elevation site. Leaf litter was the main component of litter, up to 60.49% of total litter production at the upper elevation site, while reproductive materials (flower and fruit) were the key part of litter and accounted for 50.80% (the lower elevation site) and 57.02% (the middle elevation site) of total litter production. As site elevation decreased, element stocks within total litter decreased by approximately 65.39% (organic carbon), 65.17% (total nitrogen) and 63.66% (total phosphorus), respectively, which was attributed more to element stocks within leaf litter instead of element stocks within the other litter. Results showed that site elevation decreases resulted in decreased litter production, altered composition percentages of litter production, and reduced element stocks within total litter. In the future mangrove restoration projects, it is advisable to prioritize upper elevation (above local mean level) for promoting litter production.

Mussel populations (Mytilus edulis) around the coasts of Europe and the North Atlantic are often ephemeral and have notably experienced a large decline in abundance. Since 1993, annual blue mussel stock surveys have been carried out in the Limfjorden, Denmark. We used the stock survey data combined with electronic monitoring fishing data and Mechanistic Models for the Limfjorden, providing environmental data to investigate the impact of various stressors. Multiple factors were found to affect the longevity of subtidal mussel beds in Limfjorden. Predation by starfish, fishing activities, shell length of the mussels, amplitude in summer temperature and consecutive days of oxygen depletion decreased the longevity of the beds. Conversely, increased biomass, multiple cohorts and increasing water depth demonstrate stabilising effects. Water column stratification had both a negative and positive impact on bed longevity depending on the duration. These analyses can help inform environmental, conservation, and fisheries managers on the long-term trends of population dynamics and gain a deeper understanding of what factors can affect mussel bed longevity in the context of declining stocks.

Investigating the potential and mechanisms of thermal adaptability in scleractinian corals is critical for aiding corals in dealing with global warming and improving the efficiency of coral reef restoration efforts. Although thermal acclimation facilitates the resistance of branching corals to thermal stress, little is known about the physiological processes of massive and platy corals in the South China Sea or their ability to adapt to heat stress. In this study, we conducted indoor short-term thermal acclimation simulation experiments on three types of corals: massive Porites lutea, platy Pavona decussata, and branching Pocillopora damicornis. Subsequently, we studied the responses and adaptive mechanisms of the three corals to heat stress and explored the effects of short-term thermal acclimation using physiological and biochemical markers. The results showed that the three corals exhibited comparable phenotypic and physiological responses to heat stress, including tentacle retraction and decreases in zooxanthellae density, maximum quantum efficiency of photosystem II, and glutathione content, along with increases in antioxidant activity (catalase and superoxide dismutase), ammonium assimilation (glutamine synthetase), and apoptosis (lipid peroxide and caspase-3). Additionally, heat tolerance differed among the different species of coral. Furthermore, the physiological markers performed better in all three coral types after acclimation, and the effects of short-term acclimation decreased from P. lutea to P. damicornis to P. decussata. We propose that short-term thermal acclimation enhances the heat tolerance of corals by affecting their metabolism and antioxidant capacity. Leveraging short-term thermal acclimation in coral reef restoration efforts could help corals adapt to the threats posed by global warming and enhance restoration efficiency.

Mangroves, tidal marshes, and seagrasses have been recognized as blue carbon coastal ecosystems as they accommodate large carbon stocks, enable long-term carbon storage, have the capacity to control greenhouse gas emissions and possess the potential to reduce the rise in atmospheric CO₂ levels. In the tropical and subtropical intertidal zones, mangroves show significant productivity and rapid deposition rates. Mangroves play an important role in capturing, transforming, and storing CO₂ in the atmosphere into coastal sediments for a long time, displacing organic carbon from the coastal zone to the offshores and the ocean. Mangroves also help in preventing storms, hurricanes, coastal erosion, and tidal waves. Recently, mangroves have been threatened by natural and anthropogenic activities such as urbanization, pollution, aquaculture and tourism. They are expected to hamper their essential services, such as coastal defense, breeding grounds for aquatic organisms' seafood supply, etc. Despite the importance of mangrove forests in carbon sequestration and the numerous goods and services they offer humans, wood and non-wood forest products, food, fisheries, medicines, eco-tourism, and recreation. These mangrove ecosystems are deteriorating at alarming rates, necessitating immediate intervention. Thus, the protection, restoration and conservation of this ecosystem are gaining considerable attention from researchers across the globe. This paper provides information on different mangrove adaptations, their mechanisms, roles in the ecosystem, carbon estimation, influencing factors, threats, and conservation strategies for carbon sequestration in this invaluable coastal habitat.

With the entry into force of the International Maritime Organization's International Ballast Water Management Convention in September 2017, ships have begun to install and operate onboard ballast water management systems (BWMS) to reduce the number of live organisms in ballast water. Scientific methods were developed to assess the effectiveness of BWMS at reducing the number of live organisms in ballast water. However, detecting low organism concentrations in treated ballast water is challenging when considering the small sample volume (6 mL) analyzed for organisms in the 10–50 μm size class. The volume analyzed can be increased by concentrating the sample prior to analysis, but it is important to assess the effects of the sample concentration method due to potential cell loss experienced during the concentration step. Therefore, laboratory experiments were conducted to assess the effects of a gravity filtration method to concentrate samples to a factor of 40:1. Experiments were conducted for both low and high organism abundances. For unpreserved samples at low organism abundances (∼10 cells mL⁻¹), concentrated samples had on average 31% fewer live cells mL⁻¹ than unconcentrated samples for four out of five experiments. At high organism abundances (≥ 120 cells mL⁻¹), unpreserved concentrated samples had on average 55% fewer live cells than unconcentrated samples. Alternatively, with preserved samples at low organism abundances, concentrated samples had on average 4.5× more cells than unconcentrated samples. At high organism abundances, concentrated samples had on average 6.4× more cells than unconcentrated samples. Differences were also observed between preserved and unpreserved samples. These findings can help to improve ballast water monitoring procedures and BWMS assessments, addressing a critical challenge to maritime environmental protection.

In the past, a large part of the seabed of the southern North Sea was covered by hard substrates, including oyster beds, coarse peat banks, and glacial erratics. Human activities, particularly bottom trawl fisheries, led to the disappearance of most of these hard substrates, resulting in the loss of its associated diverse benthic life as well. However, the introduction of human-made structures such as offshore wind farms in the North Sea, offers a chance to provide habitat of similar functionality as the former hard substrates. The offshore wind farm infrastructure generally contains layers of rock material deployed at the base of the wind turbine foundations and cable crossings, so-called scour protection, aiming to prevent seabed erosion. The scour protection offers a unique habitat for rock-dwelling benthic organisms in an otherwise mostly soft-bottom environment. By designing the scour protection to be more nature-inclusive, the biodiversity of benthic life can be increased. In this study we examined the effect of substrate material and grading of the scour protection on the epibenthic biodiversity in situ. This was done by deploying research cages containing crates (n = 15) with different types of substrates (concrete, granite, and marble) on the scour protection within an offshore wind farm in the Dutch North Sea. The study revealed a significant (p < 0.05) positive relation between available substrate surface (pebble size) and taxonomic richness. Furthermore, a biological trait assessment of living habits (Tube dwelling, Burrowing, Free living, Crevice dwelling, Epi/endobiotic, and Attached) revealed variations in habit modes across substrate types, with marble and concrete samples showing greatest divergence. Marble samples contained a higher prevalence of tube dwelling organisms, whereas concrete samples contained a relatively higher prevalence of free living, epi/endobiotic and crevice dwelling organisms. The findings support the value of nature-inclusive scour protection designs, emphasizing that both taxonomic and functional diversity can be enhanced by increasing the available surface area of the scour protection and incorporating a variety of substrate types. By adopting these nature-inclusive design components, the coexistence of renewable energy production and a diverse marine benthic community can be further optimized.

Dynamic influences of ocean processes on distribution, abundance, and diversity of zooplankton communities were studied over the continental shelf in the northern Gulf of Mexico (GoM) from 2015 to 2017. Zooplankton sampling was conducted on four summer cruises in the northcentral GoM. Sampling was designed in waters potentially influenced by the Loop Current (LC) and/or Mississippi River discharge to assess the impacts of these two mesoscale features on the abundance and diversity of zooplankton. During the three-year study, the LC displayed distinct spatial-temporal variations in penetration and occurrence in the northern GoM. Environmental conditions (i.e., sea surface temperature, salinity, and dissolved oxygen) varied between months and years sampled, and were significantly different among cruises (ANOVA, p < 0.001). The majority of zooplankton consisted of calanoid copepods (65% ± 7.2%, mean ± SD), while non-copepod taxa were primarily chaetognaths, polychaetes, tunicates, and ostracods (23 ± 9.2%). Species abundance and diversity of zooplankton were significantly correlated with sea surface temperature, salinity, and dissolved oxygen (p < 0.05). Canonical correspondence analysis displayed significant associations between mesoscale features and dominant zooplankton groups among cruises and by taxa (Monte Carlo Permutation Test, p < 0.001). In addition, non-metric multidimensional scaling indicated that zooplankton assemblages were distinct, likely caused by Mississippi River plumes during the study period. As one of the few efforts to examine zooplankton dynamics at a low taxon level over the GoM continental shelf regarding the impact of mesoscale features, this study revealed seasonal (i.e. summer) and spatial patterns in distribution, abundance, and diversity of zooplankton communities subjected to the dynamic physicochemical conditions in the northern GoM, which will continue in a changing climate.

The delimitation of fish stocks and how species use habitats are essential keys to develop and to implement fishery resources management and rational sustainable programs. Otolith shape and microchemistry analyses can provide helpful information for defining population units and solving ecological connectivity issues. The black drum, Pogonias courbina, is an important fishery resource in the southeastern Brazil lagoon systems, and is considered a vulnerable fish according to the IUCN Red List of Threatened Species. Thus, the present study aimed to understand the population structure and habitat connectivity of P. courbina in two lagoon systems in the south-east coast of Rio de Janeiro, Brazil. A total of 60 individuals were collected from the lagoons of Saquarema (SQ) and Araruama (AR), between November 2019 and April 2020. Thirty individuals from each location, all estimated to be two years old based on the counting of the annual growth increments, were used. The composition (multi-elemental signatures – MES) and shape (elliptic Fourier descriptors – EFD) of the sagittal otoliths were integrated to evaluate the population structure and the habitat connectivity of the fish inside these lagoon systems. EFD showed differences between lagoon systems, with an overall reclassification rate of 97%. The MES exhibited distinct patterns between lagoon systems, mainly driven by differences in Ba/Ca, Co/Ca, Li/Ca, Mg/Ca, Ni/Ca, Sr/Ca, and Zn/Ca ratios. The overall reclassification rate for MES was also 97% (93% and 100% for SQ and ARA, respectively). The overall reclassification rate obtained using both EFD and MES was 98%. The results suggest a clear spatial discrimination and low connectivity between these groups of two years old P. coubina individuals living in the studied lagoon systems. These findings imply that small-scale artisanal fisheries in the lagoon systems require more attention, aiming to maximize local management strategies for commercially exploited species.