The isotopic compositions (δ¹³C and δ¹⁵N) and C/N ratios of suspended particulate organic matter (POM) were investigated off the east coast of Hainan Island in the South China Sea during summer. Coastal upwelling influenced the nearshore stations of transects S2 and S3, and higher δ¹³C and δ¹⁵N values suggested that coastal upwelling played a significant role in determining the POM sources. The POM at the nearshore area of transect S1 was controlled by the coastal current and freshwater discharge. Additionally, organic matter may be transported to the offshore area via tidal movements in transects S1 and S3. Based on the stable isotope analysis in an R model, the marine organic matter contribution in the upwelling area (19%) was higher than that in the other areas (transect S1 and the offshore area) (7%). The δ¹³C and δ¹⁵N values and C/N ratios reflect the carbon and nitrogen sources and their cycling in the upwelling zone off the east coast of Hainan Island.

Metal contamination can change ecological interactions with potential effects on community dynamics. However, understanding real effects of metals on biota relies on studies undertaken in natural conditions. Through a field experiment, we investigated the effects of copper contamination on the responses of a barnacle prey and its predator, the dogwhelk, and explicitly their interaction. Contamination increased barnacle mortality and reduced predation with no effects on interaction strength. This was because the higher mortality of the prey compensated for the lower consumption of the predator. Despite not affecting the interaction strength, these results suggest a decrease in energy flow in the trophic chain that may lead to important changes in community structure and ecosystem functioning. This study shows the importance of manipulative experiments designed to provide mechanistic insights into ecological interactions to better clarify the effect of stressors on the structure and dynamic of communities.

In a Mediterranean lagoon characterized by high levels of Hg in the sediment, Hg content in commercial fish species was determined, and, in order to establish Hg concentration in the water column, Diffusive Gradient in Thin films technique (DGT) was used. The results allowed to state (1) the disturbance of the surface sediment and its resuspension in the water column did not cause detectable increase in Hg releases, (2) the East basin acted more than the West one in contamination of fish species, (3) the small-sized sea-breams (<400 g) were more contaminated than larger sizes ones (>400 g). We concluded: (1) fish contamination may also depend on direct contact with releases of the contaminant and small, gregarious and less sedentary subjects are more likely to incur releases of Hg; (2) Hg releases can be greater in areas with a relatively low sedimentary organic matter load compared to areas subjected to high density macroalgal mat, regardless of the amount of Hg present in the sediments; (3) wind transport of plant masses in low energy storage areas, may constitute an increase factor of Hg in the sediment. A critical review of the results was made in comparison with the available literature reports and some hypotheses were proposed regarding the possible dynamics and availability of the contaminant.

Marine sediments serve as a sink for environmental pollutants, such as lipophilic marine phycotoxins (LMPs). To reveal the fate of LMPs, we studied their distribution characteristics in sediments. From January 2016 to August 2017, we sampled surface sediments from Jiaozhou Bay (JZB) of the North Yellow Sea, and their solid-phase extracts were analyzed using liquid chromatography-tandem mass spectrometry. Three LMPs viz. okadaic acid (OA), dinophysistoxin-1 (DTX1), and pectentoxin-2 (PTX2) were predominant in the sediments. Also, PTX2 distribution was more extensive in the area, while OA and DTX1 were more concentrated. Having the same toxigenic algae origin, the spatial distribution of OA, DTX1, and PTX2 in the sediments was similar.

There is limited understanding on nearshore fish community functioning in relation to changing environmental gradients. To address this, we investigated the trait composition of fish communities in five regions along the Portuguese coast during 4 years. Northern regions were characterized by higher Chlorophyll-α and small-sized species with short lifespans. The southernmost region was characterized by warmer waters, more intense upwelling events and typical warm-water species. Higher species richness and functional redundancy at the southernmost region suggested that in case of potential species loss, community functioning would be less affected in this region, and thus, a certain level of community resilience is maintained. The central region presented lower functional redundancy and high functional richness, which indicated the presence of rare species with rare traits, suggesting a more vulnerable community. This information on the nearshore fish community distribution may be particularly important towards managing coastal ecosystems in response to changing environmental conditions.

Surface microplastics were sampled monthly in four tropical bays (Manzanillo, Santiago, Navidad and Cuastecomates) of the central Mexican Pacific during March 2017 to February 2018. Microplastic concentrations ranged between 0.01 and 1.05 particles/m² with a median per bay ranging between 0.26 and 0.40 particles/m². Raman spectroscopy registered polypropylene (40%), polyethylene (40%) and polyester (20%) polymers. Fibers dominated all samples, except for Manzanillo where fragments numerically dominated during the rainy season (Jun-Oct). Fiber concentration was not significantly different among bays or seasons, likely associated with continuous wastewater discharge. Fragment concentrations were significantly higher in Bahía Manzanillo and Santiago than the other two bays. Non-metric multidimensional scaling showed distinct distribution of Manzanillo samples (which has important port activities) as compared to Santiago, Navidad, Cuastecomates (where tourism economic activities predominate). This first direct comparison of sea surface microplastic concentration among four bays in Mexico provides a baseline to study impacts on marine zooplankton in this tropical ecosystem.

Very Low Sulfur Fuel Oils (VSLFO, <0.5% S) are a new class of marine fuel oils, introduced to meet recent International Maritime Organization regulations. The MV Wakashio was reported to have released 1000 t of VLSFO when it grounded on a reef in Mauritius on 25th July 2020. A field sample of oily residue contaminating the Mauritian coast was collected on 16th August 2020 and compared with the Wakashio fuel oil. Both oils were analyzed for organic and elemental content, and stable isotope ratios δ¹³C and δ²H measured. Comprehensive two-dimensional gas chromatography with high-resolution mass spectrometry was used to identify and compare biomarkers resistant to weathering. The aromatic content in the VLSFO was relatively low suggesting that the potential for ecosystem harm arising from exposure to toxic components may be less than with traditional fuel oil spills. The Wakashio oil spill is, to our knowledge, the first documented spill involving VLSFO.

A two-dimensional hydrodynamic model that couples hydrology and water quality processes was developed to simulate the concentrations of PAH in water phase and sedimentation rates of PAHs in marine environment. The kinetic processes of the model included atmospheric exchange, transportation, deposition, etc. Taking Liaodong Bay as an example, the pollution level, spatial distribution of PAHs in sediments were analyzed and the transport, transformation and sedimentation processes of PAHs were simulated. The results show that PAHs concentrations in sediments are at a “moderate risk” level, and the distribution has a conspicuous spatial variation. According to the results of simulation, the PAHs in sediments are easily accumulated with weak hydrodynamic conditions. Thus, hydrodynamic is one of the important factors affecting the spatial distribution characteristics of PAHs in the sediments. The PAHs numerical calculation model established in this paper and its evaluation results have important research value for PAHs pollution prevention and control.

Marine debris is a global issue with adverse impacts on marine organisms, ecological processes, aesthetics, and economies of nations. Several studies have been conducted to quantify the plastic debris along Indian beaches. This baseline study describes the results of a survey conducted on the types of plastic litters and their quantification during January to March 2020 along Mandvi beach in Gujarat. A quadrate having 10 × 10 m size was used for sampling the plastic litter on the shoreline. A total of 10 quadrates along the shore was considered for quantification of the plastic materials based on their density, color, and weight. The plastic material observed includes gutkha pouches, food wrappers, and fragments, along with plastic straws, cutleries, and fragments of various dimensions and thickness. The major contributing factors for the debris abundance in Mandvi beach are land-based sources and recreational activities. The results suggest that similar long-term projects covering extensive areas should be undertaken for accurate quantification of available debris and their impacts on coastal habitats of Gujarat.

Understanding of the pre-development, baseline denudation rates that deliver sediment to the Great Barrier Reef (GBR) has been elusive. Cosmogenic ¹⁰Be in sediment is a useful integrator of denudation rates and sediment yields averaged over large spatial and temporal scales. This study presents ¹⁰Be data from 71 sites across 11 catchments draining to the GBR: representing 80% of the GBR catchment area and provide background sediment yields for the region. Modern, short-term, sediment yields derived from suspended load concentrations are compared to the ¹⁰Be data to calculate an Accelerated Erosion Factor (AEF) that highlights denudation “hot-spots” where sediment yields have increased over the long-term background values. The AEF results show that 58% basins have higher modern sediment yields than long-term yields. The AEF is considered a useful approach to help prioritise on-ground investments in remediation and the additional measured empirical data in this paper will help support future predictive models.