The present study attempts to decipher the seasonal variations in hydro-geochemistry of groundwater in the Terekhol River Basin, western coastal region, Maharashtra, India. A total of 65 groundwater samples of post-monsoon (POMS) and pre-monsoon (PRMS) seasons were collected and analyzed for major ion composition using standard analytical procedures of APHA. Piper and Gibbs plots is used to elucidate the controlling factors which altering the groundwater composition. Scatter plots of ions indicate that major ions from lithologies exposed in the study area and anthropogenic activities are altering the groundwater chemistry. Statistical analysis includes correlation, factor analysis and cluster analysis used to interpret the hydrochemical data. As compared to the WHO drinking standards, all the groundwater samples are fit for drinking. Irrigation water suitability was ascertained based on SAR, %Na and KR indices. Overall, the groundwater chemistry in study area is reflects changes in natural processes rather than anthropogenic inputs.

For understanding the significance of tidal pumping for driving submarine groundwater discharge (SGD), two time series observations were conducted over tidal cycles in typical mariculture areas of Sanmen Bay, China. Based on ²²⁴Ra and dissolved silicon (DSi), the tide-driven SGD fluxes showed significant negative correlations with tidal height, and were 16.4 ± 5.6 cm d⁻¹ and 21.7 ± 13.9 cm d⁻¹ at two coastal sites of the Sanmen Bay, highlighting the potential of DSi in SGD calculation when coastal waters are on short time scales. Furthermore, nutrient fluxes through tidally influenced SGD were estimated to be 11.5–26.5 mmol m⁻² d⁻¹ for dissolved inorganic nitrogen, 0.06–0.34 mmol m⁻² d⁻¹ for dissolved inorganic phosphorus and 11.5–32.1 mmol m⁻² d⁻¹ for DSi, which were higher than those from surface loadings, revealing that tide-driven SGD with large amounts of nutrient and high N:P ratios may significantly contribute to the development of marine aquaculture.

Plastic waste is a ubiquitous form of marine pollution and recent studies have identified threats of plastic debris and the associated chemical compounds to wildlife. Sponges pump substantial quantities of water and are important in benthic-pelagic coupling, making them susceptible to interacting with such pollutants in the water column. Here, a method to detect common plastic-associated compounds including phthalates, a phthalate metabolite, bisphenol-A, and a brominated flame retardant in sponge tissue was developed. The method was applied to samples of Xestospongia muta and Niphates digitalis from a reef in the Florida Keys. All sponge samples had quantifiable levels of di(2-ethylhexyl) phthalate, with trace levels of the associated metabolite detected in some N. digitalis samples. There was no quantifiable detection of bisphenol-A, or the brominated flame retardant. This work is a preliminary assessment of the relationship between plastic marine debris and marine sponges.

Dissolved heavy metal pollution in the ocean is becoming an environmental concern. Their distribution patterns are complex and influenced by multiple factors in the coastal ocean. Therefore, more investigations are needed to understand their behavior in the seawater. This study systematically investigated the distribution of Cu, Pb, Cd, As, Zn and seawater properties in the surface and bottom water off the Yangtze River Estuary, East China Sea in spring, summer and autumn, 2019. The results showed significant spatiotemporal distribution that three-zone-pattern of estuary, nearshore, and offshore can be divided. While sources, hydrodynamics, biological uptake and sediment resuspension affected the overall distribution, dissolved oxygen and pH dominantly influenced the estuary and offshore respectively, with more complex factors in the nearshore. Low ecological risks were assessed during the study, but global warming, ocean acidification and hypoxia are essential concerns to understand the biogeochemistry of dissolved heavy metals in the ocean.

Microplastics (MPs) in mariculture environments may have an impact on mariculture and ecosystems. This study sampled the sediments in mariculture ponds and offshore areas in Qingduizi Bay during winter and summer. The abundance, characteristics, spatiotemporal distribution and pollution risk of microplastics were analyzed. The results showed that the abundance of MPs in the mariculture pond and offshore area was 49.2 ± 35.9 items·kg⁻¹ d.w. and 17.1 ± 9.9 items·kg⁻¹ d.w.; the MPs were mainly composed of transparent fibers of thickness 2000–5000 μm, with the main polymers being polyethylene terephthalate (PET) and cellophane (CP). The spatial distribution showed a downward trend from the inside to the outside, but the difference was not significant when comparing different seasons. The pollution load index (PLI) risk assessment showed that all sampling sites were at Hazard Level I. This study can provide valuable information for the risk assessment of microplastic pollution in mariculture areas.

The present study aims to analyze the level and total toxicity of the most common pollutants in surface sediments and assess their impact on the occurrence of antibiotic resistance genes (ARGs) in the Sea of Azov. Biotesting using the whole-cell bacterial lux-biosensors showed high integral toxicity of surface sediments and the presence of genotoxicants and substances that cause oxidative stress and protein damage. Using cluster analysis, it was shown that the distribution of pollutants in the Sea of Azov depends on the type of surface sediments. The relative abundance and distribution of 14 ARGs in surface sediments were shown. Principle component analyses results suggest that non-corresponding contaminants do not exert direct influence on the ARGs abundance in the surface sediments of the Sea of Azov. Thus, the need to investigate the significance of non-corresponding pollutants in the selection and distribution of ARGs in the aquatic environment remains a pressing problem.

In this study, we explored the heavy metal elements in 42 surface sediments from the Malacca Strait in terms of distribution, controlling factors, environmental quality, and primary sources. An analysis of grain size revealed finer sediments near the coast of Malaysia, which gradually thickened toward offshore. In addition, heavy metal elements were abundantly distributed near the coastal area of Malaysia, with a gradual decrease toward the sea; their content increased within waters close to the Perak estuary. Source analysis of heavy metals showed that Cr, Hg, Zn, Cd, and Cu were mostly derived from natural weathering, and their distribution was significantly influenced by sediment grain size. As and Pb were affected by human activities. The environmental quality assessment results showed that Cu, Cr, Cd, and Zn in our study regions were pollution-free. Pb elements showed low-to-moderate pollution, and Hg showed a certain degree of ecological risk due to its high toxicity coefficient. The content of As elements in surface sediments increased significantly when compared to the background value, with several evaluation methods indicating a high-risk index. According to these findings, the area near the mouth of the Perak River is the most polluted, followed by the surrounding coastal areas.

Metal contamination is a threat for marine ecosystems from an environmental, economic and public health perspective, particularly in regions where local communities rely on marine resources such as the Gulf of Guinea. Plankton are the point of entry for metals in the marine food web, potentially contaminating seafood. We investigated the bioaccumulation of 12 metals in three size classes of plankton from the coast of Ghana. Metal concentrations were high in the micro- and mesoplankton, in particular for Mn, Mo and Zn (up to 100 mg kg⁻¹) and Fe (>100 mg kg⁻¹). All metals significantly bioaccumulated (10³–10⁶ L kg⁻¹) and the bioaccumulation increased from the smallest to larger size fractions, suggesting a biomagnification. These metals included the highly toxic elements As, Cd and Pb. Our results highlight the need to monitor metal occurrence in the Gulf of Guinea, to reduce pollution and ensure food safety, in accordance with the UN SDG #14.

Estuarine ecosystems are considered hotspots for productivity, biogeochemical cycling and biodiversity, however, their functions and services are threatened by several anthropogenic pressures. We investigated how abundance and diversity of benthic macrofauna, and their functional traits, correlate to sediment biogeochemistry and nutrient concentrations throughout an estuarine-to-hypersaline lagoon. Benthic communities and functional traits were significantly different across the sites analysed, with higher abundance and more traits expressed in the estuarine region. The results revealed that the benthic trait differences correlated with sediment biogeochemistry and nutrient concentrations in the system. The estuarine regions were dominated by high abundance of large burrowing and bioturbating macrofauna, promoting nutrient cycling and organic matter mineralisation, while these organisms were absent in the hypersaline lagoon, favouring accumulation of organic matter and nutrients in the sediment. The results highlight the importance of preserving healthy benthic communities to maintain ecosystem functioning and mitigate the potential impacts of eutrophication in estuarine ecosystems.

In this study, the abundance, and characteristics of the microplastics on the southern coast of the Black Sea were assessed. More than 70% of the detected microplastics were smaller than 2.5 mm and mostly consisted of fibers and fragments. The average microplastic abundance in the beach sediment and seawater were 64.06 ± 8.95 particles/kg and 18.68 ± 3.01 particles/m³, respectively. The western coast of the study area (Marmara region) was the most polluted area, and a spatially significant difference was determined in terms of abundance. The composition in the beach sediment (particles/kg) was dominated by styrene acrylonitrile copolymer (SAC) (40.53%), polyethylene terephthalate (PET) (38.75%), and polyethylene (PE) (6.91%), whereas the seawater (particles/m³) was dominated by PET (57.26%), PE (13.52%), and polypropylene PP (11.24%). The results of our study can be a baseline for environmental modeling studies and experimental studies on the marine organisms inhabiting the Black Sea.