Estuarine Coastal and Shelf Science最新文献

Demand for ray consumption has been increasing considerably along coastal areas of the Western Atlantic Ocean, especially Northeast Brazil. Species previously caught as bycatch are now targeted by fisheries but the available information on these species remains scarce. In the present study, we provide the first application of stable isotopes from muscle tissue (δ¹³C and δ¹⁵N) and vertebrae microchemistry (²⁴Mg, ⁴³Ca, ⁵⁵Mn, ⁸⁶Sr, ¹³⁸Ba) data to analyze the habitat use of batoids. We employ these techniques on three sympatric demersal stingray species across different life stages. Our approach revealed entry and exit movements in estuarine areas by Hypanus guttatus, a strong specificity for coastal reef habitats for Hypanus marianae, and the use of deeper waters by adults of Hypanus berthalutzae. We also found significant between-sex differences in habitat use for H. berthalutzae, especially for elements associated with hypoxic zones (⁵⁵Mn) and salinity variations (⁸⁶Sr and ¹³⁸Ba), suggesting that males move to deeper areas farther from the coast during ontogeny. Both data sources employed were considered good descriptors for the various environments these species are found in. Our results suggest that mangroves and coral reefs are the most important areas for H. guttatus and H. marianae, respectively, while H. berthalutzae seems to use the entire continental shelf throughout its life cycle. We further discuss how these results may translate into each species distribution range and fishing pressure.

Definitions of saltmarsh vary, with approaches based on the European Union Water Framework Directive (WFD) and the Habitats Directive differing from major definitions in the literature, and from each other, giving rise to confusion and differing approaches to calculations of extent. Habitats Directive definitions also differ across Europe. This paper's main aim is to derive a detailed definition of the saltmarsh habitat that satisfies the ecological principles of saltmarsh as defined in the literature. This is then related to the Directives by examining each Directive in the context of phytosociology and UK and European Ellenberg Numbers for Salinity. A definition is offered that is precise in vegetational terms and complies with most literature definitions, notably in respect of the importance of halophytes. Although our method has been applied to the UK National Vegetation Classification, the technique can be extended to any vegetation type for which a salt tolerance index is available. Conflation of saltmarsh definition and conservation is reviewed and removed in a way that retains the ability to protect the habitat in its wider context. It is essential that all accounts of saltmarsh, and especially those that quantify extent, specify their terms of reference.

Benthic communities perform many important roles within mangrove ecosystems and are responsible for facilitating many of the functions attributed to mangrove forests. For instance, they are instrumental in mediating mangrove system productivity, and provide crucial food for juvenile nekton. Despite their importance, very few studies have investigated the benthic community of mangrove forests, and among those the results are inconsistent. This variability manifests in strong location effects, with low organism density and species richness in Indo-Pacific mangroves, compared to West Atlantic sites. These regional difference are confounded by differences in within-region environmental settings (e.g. rainfall, tidal range, spatial location along the coastal mosaic), and this complicates the development of a clear understanding of underlying consistencies. To assess the influence of contrasting environmental influences on the benthic community of mangrove forests we studied the benthic community of Rhizophora stylosa forests at two coastal estuaries and along the shores of two islands within a 75 km radius. The results showed that the community composition differed among settings, with several taxa only occurring at one of the two forests type. Furthermore, Peracarida, a common prey found in the gut of juvenile fish, was only found through the island forests, but never observed within the estuarine forests. This indicates that environmental setting can play a key role in determining the nature of mangrove benthic assemblages and their potential ecological roles. Consequently, caution is required when attributing the ecological roles of mangrove forests without accounting for changes in settings. Additionally, we only investigated a single mangrove species within the same climatic region, meaning that even greater variability is likely when the full range of mangrove types, conditions and areas are assessed. Understanding this variation is important because it implies that mangrove forest restoration projects are unlikely to achieve their desired outcomes unless setting-specific conditions are understood and taken into account.

The Baltic Sea coastal lagoons are shallow reservoirs affected by eutrophication which is manifested by, inter alia, persistent phytoplankton blooms the remains of which (phytodetritus) sink to the bottom. The research in the Szczecin Lagoon (a component of the River Odra/Oder estuary in the south-western Baltic Sea) was aimed at finding out whether (a) the autochthonous primary production, specifically the resultant phytodetritus sedimentation, was the main pathway of the sediment organic enrichment, (b) the deposition of the phytoplankton material elicited temporal and spatial responses in the Lagoon's sediment visible as changes in its organic enrichment metrics. The data were collected monthly (April–November) in 2010 (a ‘wet’ year, with a higher river water supply) and 2011 (a ‘dry’ year), from 5 stations differing in the hydrodynamic regime (two stations situated in erosional and three in depositional areas). The study revealed the presence of climatic controls over the Lagoon system manifested as differences in the phytoplankton biomass between the wet and the dry year, with a higher biomass in the latter. There were also hydrodynamic controls (depositional vs. erosional bottoms) over the ability of the sediment to accumulate and retain organic material supplied primarily by the autochthonous primary production of the phytoplankton and microphytobenthos. Differences between the depositional and erosional areas were visible also as differences in the dominant marker pigments, with fucoxanthin (diatoms) being characteristic of the erosional stations and zeaxanthin (cyanobacteria) and lutein (chlorophytes) being typical of depositional areas. In addition, the study provided evidence for the persisting eutrophication of the Lagoon, manifested as high values of the phytoplankton biomass marker (chlorophyll a). The high organic enrichment of the sediments was shown to be decoupled from, but sustained by, the autochthonous plant biomass supply.

The highly efficient carbon storage capacity of beds formed by Posidonia oceanica, an endemic Mediterranean seagrass species, has been widely recognized. Recently, the supra-littoral deposits of leaf litter (i.e., banquettes) have been investigated in terms of their nutrients, biomass and associated community. Nevertheless, an overlooked fraction of the P. oceanica detritus never reaches the shore and sinks far away to deeper seafloor. Additionally, part of the supra-littoral deposit goes back to the sea during winter swells. This deep detrital compartment, mainly composed of sediment mixed with dead leaves and rhizomes coming from P. oceanica beds, has only been described once by Pères in 1953, who focused on the macrofaunal component. Here, we investigated for the first time the meiofaunal community inhabiting sediments characterized by P. oceanica detritus in a deposit located at 65−80 m depth off the Ischia Island (Gulf of Naples, Italy, Tyrrhenian Sea). Our results show that the meiofaunal community appears highly diversified and strongly dominated by nematodes (from 85% to 93%). Differences in meiobenthic assemblage structures were significant only when rare taxa were considered (i.e. taxa found in low abundances and characterized by a sporadic distribution in the study area). The nematode community revealed a very high biodiversity (number of families and genera: 31 and 104, respectively), with a clear prevalence of selective and non-selective deposit feeders that suggest the key role of this habitat in the benthic detrital food web. The richness of meiofauna and the taxonomic and functional diversity of the nematode assemblages account for a “good” to “moderate” ecological quality status. These findings support the high ecological value of the macerating seagrass bottoms, an overlooked component of the blue carbon cycle that deserves to be further investigated.

Background

Nitrogen significantly influences plant performance and vegetation development in nutrient-poor ecosystems like coastal dunes. While various sources contribute nitrogen, including N₂ fixation and marine inputs, the significance of seawater spray remains understudied. In this study, we aimed to assess the relevance of seawater spray as a source of nitrogen input and its potential role in plant community composition in dune ecosystems.

Methods

The δ¹⁵N, δ¹³C, N, and C content of leaves from the most abundant 21 species were measured in 6 positions across a beach inland gradient in a Mediterranean dune system in SW Spain. Soil samples at different depths were collected in each position and N, C, P, K, NH4⁺, NO3⁼, and organic matter were measured. Salt spray accumulation was determined on Achillea maritima leaves across the gradient.

Results

Leaf nitrogen content did not exhibit a beach-inland gradient, but δ¹⁵N decreased with distance from the sea. Species displayed three distinct N uptake strategies along the gradient: species from Upper Beach and Foredune communities showed high δ¹⁵N values, suggesting a marine origin; species distributed across the gradient exhibited decreasing δ¹⁵N patterns from the Upper Beach to the Inland, indicative of seawater spray influence; species farthest from the sea relied on non-marine nitrogen sources.

Conclusions

These results indicate the importance of seawater nitrogen income for the dune system vegetation and evidence that dune plant species exhibit varied N uptake strategies influenced by their position across the beach-inland gradient.

As the intersection between land and sea, the estuary is a hotpot for natural and human-induced processes that affect its physical and chemical characteristics, as well as biodiversity and ecosystems. Due to a combination of freshwater discharge and the unique topography of river estuaries, submesoscales with a spatial scale of O(1) km can be easily generated due to the presence of strong salinity fronts at river estuaries. As the biggest river in Asia, the basically dynamical characteristics and their seasonal mechanisms of submesoscales at the Yangtze estuary remain unclear. Using a nested high-resolution (300 m) simulation established by the Coastal and Regional Ocean Community model (CROCO), the seasonal variability of submesoscales at the Yangtze estuary is investigated and the underlying generation mechanisms are analyzed based on the analysis of kinetic energy budget. The results of normalized relative vorticity, horizontal salinity gradient, and submesoscale kinetic energy (SMKE) show that submesoscale processes have a seasonal variation at the Yangtze estuary. This seasonality is tightly related to the freshwater input with a correlation coefficient of up to 0.66 (the confidence level >99%). To figure out the dominant energy sources that control the SMKE budget, five terms including the baroclinic term (BC), the barotropic term (BT), the advection of submesoscale kinetic energy term (ADK), the pressure work term (PW), and vertical mixing term (VM) are diagnosed. The results suggest that BC, BT, and PW are the source producing SMKE, while ADK and VM tend to dissipate SMKE. This work suggests the important role of submesoscale activities in the energy cascade and enhancing the transports of tracers at the estuary.

Chemotaxonomic analysis, a functionally efficient method, was performed every week over a year in the semi-enclosed Jangmok Bay to determine the composition of major phytoplankton assemblages, including small phytoplankton. Multiple blooms occurred through a year: two in summer and one in fall. The high abundance of diatoms in summer resulted in an intensive bloom of cryptophytes with a one-week time lag, followed by a dinoflagellate bloom in the fall. Additional microscopic analysis revealed an ecological succession of major phytoplankton species: a bloom of fast-growing Pseudo-nizschia sp. in summer was replaced by a bloom of Cryptomonas sp. one week after the diatom bloom, and then further succeeded to an Akashiwo sanguinea bloom in fall. The dominance of relatively small-sized Cryptomonas sp. led to a mismatch between the microscopic and chemotaxonomic results during the second bloom, indicating size dependence. In contrast, for the Akashiwo bloom, the microscope analysis was significantly underestimated by the chemotaxonomic analysis. Additionally, the ecological traits inherited by bloom-forming species play a role in their bloom dynamics. This study highlighted that the frequent sampling with the rapid HPLC analysis is effective for accurately understanding spatiotemporal variations of blooms, and can be an invaluable strategy for early warning and understanding bloom patterns in changing coastal ecosystems.