Concentrations of total mercury, total selenium, and cadmium ([THg], [TSe], [Cd]) were determined in hair of California sea lion (Zalophus californianus) pups from four islands of the Gulf of California and the Baja California Pacific coast (NG, CG, NP, and CP) to identify geographical differences and the effect of Se against Hg toxicity (TSe:THg molar ratio). THg displayed a strong north-south trend for both ecoregions, while TSe presented a significantly high concentration only for CG. TSe:THg molar ratios decreased when [THg] increased, with the lowest ratios presenting in NG pups, in which [THg] exceeded toxicological thresholds of concern. [Cd] presented similar values at all study sites except CG, which presented the lowest level. The present study shows that proximity to urbanized coastal areas has a strong influence on [THg] in pups, while [TSe] and [Cd] are probably more related to the physiological requirements of the species, and environmental conditions.

Oysters and clams are abundant and popularly consumed seafood in Viet Nam. These bivalves were proved to be suitable bioindicators to assess the heavy metal accumulation in the aquatic environment. The study is to investigate heavy metals such as As, Cd, Hg and Pb in the cultured oysters Saccostrea glomerata and clams Meretrix lyrata collected in VanDon - Quang Ninh, and CatBa - Hai Phong. The results showed that the metal heavy concentrations in the oysters Saccostrea glomerata and clams Meretrix lyrata presented in the order of As > Cd > Pb > Hg. The most polluted concentration with As among four heavy metals studied in six sampling sites was 2.81 ± 1.07 and 1.6 ± 0.62 mg/kg wet weight for clams and oysters, respectively. Investigated heavy metals in cultured oysters and clams indicated potential risks for human health in future by assessment of the heavy metals.

Based on survey data from the Bohai Sea of China in autumn (October) and winter (December) 2019, the structural characteristics of phytoplankton communities and their relationship with environmental factors were analysed. A total of 114 species of phytoplankton belonging to 84 genera and 3 phyla were identified. Warm-water species occurred frequently but cold-water species decreased in the Bohai Sea. This was associated with global warming and rising water temperatures. By comparing with historical data, Paralia sulcata gradually flourished and became the dominant species in autumn and winter, whereas the dominance of Skeletonema costatum decreased. The marine environment of the Bohai Sea has improved significantly in recent years, and phytoplankton biodiversity has increased. In autumn, both total phytoplankton and dinoflagellates were negatively correlated with salinity, and Pseudo-nitzschia delicatissima was positively correlated with nitrite and ammonia nitrogen. In winter, Nitzschia spp. showed a positive correlation with nitrate and a negative correlation with salinity.

The seasonal pattern of microplastics (MPs) contamination of the French littoral area of the Pertuis Charentais, one of the main French shellfish production regions, was assessed for the first time, between May 2019 and May 2020 at four different sites. The reference site was located at “Ile de Ré” and the other sites were located in the estuaries of the Sèvre Niortaise, Charente and Seudre rivers. Both blue mussels (Mytilus edulis) and Pacific oysters (Magallana gigas), that are considered sentinel species for the quality of the marine environment were analysed, along with sediment and seawater samples. MPs were extracted from each sample, counted, measured and sorted by colour and type. Micro-Raman spectroscopy was used to determine the proportion of confirmed MPs and the polymer types. The results showed that the contamination of mussels by fibres and fragments (1.9 ± 2.1 MPs/g ww) was significantly higher than for oysters (0.4 ± 0.4 MPs/g ww). Specifically, the contamination by fibres in both species was significantly greater than the contamination by fragments. Significant variations of MPs contamination were observed across the seasons and sites in bivalves, and depended on the species and the type of MPs (fibres or fragments). Mean concentrations of MPs measured in water and sediment were 0.007 MPs/L and 210 MPs/kg dw, respectively. Finally, blue was the dominant colour for fibres (79 %) and fragments (81 %). Blue fragments were mainly made of PS (70 %) followed by PC (18 %) and PP, PA or PLA (3 %) whereas blue fibres were mainly made of PA (80 %) followed by PET (13 %) or PP (7 %). This rare environmental case study of long-term chronic exposure of farming areas to MPs provides new knowledge on in situ variations of plastic fibres and fragments contamination throughout the seasons.

The pollution characteristics, potential sources, and potential ecological risk of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the Hangzhou Bay (HZB) and East China Sea (ECS). Total OCPs concentration ranged from 2.62 to 102.07 ng/L and 4.41 to 75.79 μg/kg in the seawater and sediment samples, with PCBs concentration in the range of 0.40–51.75 ng/L and 0.80–45.54 μg/kg, respectively. The OCPs were positively correlated with nutrients, whereas PCBs presented a negative correlation. The newly imported dichlorodiphenyltrichloroethane (DDT) in HZB is mainly the mixing of technical DDT and dicofol sources. The PCB source composition is more likely related to the mixture of Kanechlor 300, 400, Aroclor 1016, 1242, and Aroclor 1248. Risk assessment results indicate that OCPs posed low risk in seawater. The potential risk of DDTs in the sediments is a cause of concern.

As an important biological indicator, multivariate dispersion in homogeneity of an observed community is a useful parameter for bioassessment of environmental heterogeneity. To identify the influence of tidal events on homogeneity of protozoan periphyton fauna from the highest tideline to the lowest, a 1-month baseline survey was carried out along five tidelines (sites A–E) in an intertidal zone of the Yellow Sea, northern China. There was a significant influence of tidal events on the homogeneity in both compositional and community structure among five tidelines. The β-diversity measures generally decreased from the highest tideline to the lowest. The biodiversity indices of the protozoans dropped sharply from the highest to the middle tidelines, followed by an increase until to the lowest tideline. These findings suggest that the homogeneity of protozoan periphyton in both species composition and relative abundance was significantly shaped by the environmental heterogeneity in intertidal zones of marine ecosystems.

The effects of reduced forms of nitrogen (NH₄⁺ and dissolved organic nitrogen (DON)) on the spatial distribution of diatoms and dinoflagellates in an estuarine-coastal water continuum were investigated from 2015 to 2019. The proportion of non-DIN in total nitrogen was utilized as an indicator of DON along with direct measurements of DON. While NO₃⁻ originated from Seomjin River, the abundant NH₄⁺ and DON occurred from Gwangyang Bay through Namhae. Diatoms were mostly confined to the upper estuarine system and dinoflagellates dominated in the regions with high levels of NH₄⁺ and DON. Generalized additive models also presented the different responses of diatoms and dinoflagellates to increases in NH₄⁺ and DON. Thus, our results highlight that diatoms dominate in NO₃⁻-replete water with full access to the source and dinoflagellates take over the ecologically open niche in an anthropogenically polluted estuary with full access to reduced forms of nitrogen.

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources.

The oceanic acidification and coastal hypoxia have potential to enhance biological uptake of dissolved iron (Fe) by phytoplankton. In this study, the Fe uptake rate (FeUR) in Daya Bay was significantly negatively correlated with pH and dissolved oxygen (DO) (r = −0.81 and −0.73, respectively, p < 0.001). In addition, binary regression (FeUR = −1.45 × pH − 0.10 × DO + 13.64) also indicated that both pH and DO played key roles in FeUR variations. As pH and DO decreased, Fe uptake by phytoplankton was promoted, and the contribution of nano-phytoplankton to Fe uptake increased significantly, while that of pico-FeUR decreased. These will result in the phytoplankton community to be miniaturized and Fe requirement of phytoplankton goes higher, thereby leading changes of phytoplankton composition and coastal ecosystem. This study helps to understand how Fe could affect the coastal ecosystem under the increasing anthropogenic influences.

Trace Metals (TMs: Pb, Zn, Cu, Cr, Cd, and Ni), major elements (Al and Fe) and radionuclides (²¹⁰Pb/¹³⁷Cs) investigations on EL-C01 sediment core provides new information on sedimentary regime and anthropogenic impacts during the last 175 years in the Po river prodelta area. The results allow to identify some TMs/Al peak in the upper part of the core, likely related to the major flood events of the Po river during the XXth century. Sediments deposited after the year 1900 exhibit a gradual increase of some TMs concentrations compared to pre-industrial era values. In particular, Pb, Zn, and Cu high contents are detected after the World War II and during the “Italian Economic Miracle” period. The decrease of heavy metal (Zn and Pb) contents from the second half of the 1980s is probably the effect of the Italian Law 319/76 and anti-pollution environmental policies concerning industrial and urban emitters.