Biocides used in offshore oil and gas operations could be present in water discharges, and thus identifying such chemicals and their hazard could help address concerns regarding non-target organisms. Aquatic toxicity data, queried from different sources and augmented with predictive models, were used to develop species sensitivity distributions and their corresponding 5th percentile hazard concentrations (HC5s). Curated data, including over 1000 empirical records for 137 species, indicated no evidence of bias when comparing sensitivity between marine and freshwater species, even when predicted data were used. HC5s facilitated estimation of an acute-to-chronic ratio (ACR = 10), appropriate for most chemicals and useful in filling data gaps. Comparison of chronic-HC5s with the default approach for deriving predicted no effect concentrations showed that the latter systematically overstates aquatic hazard. The present approach shows promise of using acute-to-chronic HC5 ratios for defining assessment factors for different chemical classes, instead of the use of generic assessment factors.

Plastic additives are utilized during the production of plastic to modify the attributes and stability of the polymer. As oceanic plastic waste degrades, these additives can leach, and are harmful to global marine ecosystems. Despite the high abundance of additives leached into the marine environment, little is known about their direct impact on marine zooplankton. Here we test for impacts of four plastic additives, UV-327, Irganox 1010, DEHP, and methylparaben, all commonly used in plastic manufacturing, on purple sea urchin (Strongylocentrotus purpuratus) larval growth and survival in a serial dose response for 4 days. Methylparaben, UV-327, and Irganox 1010 significantly reduced larval body length by about 5% for at least one dose. In contrast, all compounds reduced larval survival by 20–70% with strongest effects at intermediate rather than high doses. Our results highlight that plastic additives should be tested for their effects on marine organisms.

The Severn Estuary is a large macrotidal estuary which includes an extensive mudflat with microphytobenthos (MPB) playing a key role in the ecosystem. This study evaluated the impact of chlorination at two different dosing levels (0.05 and 0.5 mg/l as total residual oxidants, TRO, representative of potential concentrations in the mixing zone and within the cooling water systems of a power station) on a MPB community representative of the Severn Estuary. Biomass and diversity were not negatively impacted while physiology was partially affected at the beginning of the experiment, and it recovered towards the end of the experiment. Further investigations for diversity are needed to consolidate our findings. In conclusion our results show that MPB is resilient to chlorination up to a concentration of 0.5 mg/l which is much higher (>10 times) than what might be expected near the chlorinated discharges for most coastal power stations.

This study has been carried out to understand the geochemistry of elements namely, iron (Fe) and phosphorus (P) in the core sediments of an urbanized tropical mangrove ecosystem along the Southwest coast of India. The study revealed the coupling of iron and phosphorus in which the reductive conditions induced reductive dissolution and upward transport of Fe, causing surface coprecipitation of phosphorus incorporated Fe oxyhydroxides. The accumulation and transformation of phosphorus were significantly influenced by processes viz., phosphorus regeneration due to organic matter mineralization and adsorption to inorganic iron oxides/Ca bound minerals in the surface sediments, and phosphorus retention in the sedimentary column by transformation into refractory organic phosphates. Bioavailable phosphorus (BAP) accounted for more than 50% of TP, so that the mangrove sediments act as an important internal nutrient source of iron and phosphorus for coastal eutrophication.

Laizhou Bay is plagued by many environmental problems (e.g., acidification and eutrophication) that are likely to increase in the coming decades along with social and demographic trends. We thus conducted 12 cruises from July 2019 to December 2021 in the Laizhou Bay to evaluate the potential influences of human activities on its eutrophication status. The results showed that the parameters of dissolved inorganic nitrogen (DIN) and oxygen (DO) exceeded the water quality standard in some cases during the past 3 years, suggesting DIN and DO were the crucial factors controlling water quality in the bay. Meanwhile, DIN was identified as a major pollutant in the region, and played an important role in driving the phytoplankton dynamics. Furthermore, with the increases in human-related nutrient inputs (especially DIN), the bay environment reached the mild eutrophication level and was probably at risk from excessive nutrient loads at present, further evidencing the ecosystem degradation.

Recent completion of oil fate modeling and a mass budget of the Deepwater Horizon (DWH) oil spill allows for a counter-historical study using quantitative Comparative Risk Assessment (CRA) methodology. Novel application of subsea dispersant injection (SSDI) during the response reduced surfacing oil, volatile organic carbon emissions, and oil on shorelines. The effectiveness of that application, and potential alternatives had dispersant not been used or been used more aggressively, were evaluated by modifying and comparing the validated oil fate model under different SSDI strategies. A comparison of mass balance results, exposure metrics, and CRA scoring for Valued Ecological Components (VECs) shows the value of SSDI in achieving risk reduction and tradeoffs that were made. Actual SSDI applied during the DWH oil spill reduced exposures to varying degrees for different VECs. Exposures and relative risks across the ecosystem would have been substantially reduced with more effective SSDI.

Plastics accumulate in the environment and the Mediterranean Sea is one of the most polluted sea in the world. The plastic surface is rapidly colonized by microorganisms, forming the plastisphere. Our unique sampling supplied 107 plastic pieces from 22 geographical sites from four aquatic ecosystems (river, estuary, harbor and inshore) in the south of France in order to better understand the parameters which influence biofilm composition. In parallel, 48 enrichment cultures were performed to investigate the presence of plastic degrading-bacteria in the plastisphere. In this context, we showed that the most important drivers of microbial community structure were the sampling site followed by the polymer chemical composition. The study of pathogenic genus distribution highlighted that only 11% of our plastic samples contained higher proportions of Vibrio compared to the natural environment. Finally, results of the enrichment cultures showed a selection of hydrocarbon-degrading microorganisms suggesting their potential role in the plastic degradation.

Quantification of four toxic metals (As, Cr, Cd, and Pb) in water and sediments at the Sitakunda ship breaking area in Bangladesh was studied. Along with this, sediment quality and ecological risk were evaluated for the metal intrusion to the study area. A total sample number of 120 (water; n = 60 and sediment; n = 60) were analyzed for both winter and summer seasons using atomic absorption spectrophotometer (AAS). The trace metal concentration in both water and sediment showed decreasing trend as follows; Cr (mean-W: 0.118 mg/L; mean-S:121.87 mg/kg) > Pb (mean-W: 0.064 mg/L; mean-S: 65.31 mg/kg) > As (mean-W: 0.03 mg/L; mean-S: 32.53 mg/kg) > Cd (mean-W: 0.004 mg/L; mean-S: 4.81 mg/kg). However, in both segments, the concentrations of the toxic metals exceeded the recommended acceptable limits. As and Cd showed significant variation (water and sediment) between the seasons, while Pb and Cr had no seasonal impact. Metal pollution index (MPI) and contamination factor (CF) was evaluated and revealed that the study area exhibited the critical score of water quality (MPI > 100). The cumulative effect of the metal concentrations was high (CI > 3). The assessed mean geoaccumulaiton index (Igₑₒ) revealed that the study area was moderate to strongly polluted except for Cr. According to the contamination factor (CF), the sediment samples were moderate to highly contaminated by Cd, Pb, and As. Moreover, the explored range of pollution load index (PLI) in all sampling sites in the ship breaking region was from 1.75 to 3.10, suggesting that the sediment in the study area was highly polluted by heavy metals (PLI > 1). The risk index and the potential ecological risk index (PERI) suggested that the study area was at high risk due to metals pollution. Therefore, it is obligatory to maintain some crucial efforts for the betterment of the surrounding environment near the investigated sites.

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in three sediment cores from Brunei Bay, Southern South China Sea was investigated. The total concentrations of 16 priority PAHs (∑PAH₁₆) and their alkyl-substituted derivatives ranged from 10.4 to 376 ng g⁻¹ and 30.7 to 2263 ng g⁻¹, respectively. PAH biomarker diagnostic ratios and principal component analysis (PCA) combined with absolute principal component score (APCS) and multiple linear regression (MLR) were performed to apportion the source contribution. The results revealed mixed inputs of fuel combustion residues and uncombusted petrogenic products. The downcore PAH profile revealed that the highest peaks could be related to past human activities using biofuel and coal during the industrialization/agriculture revolution period. The 1,7/(2,6+1,7)-dimethylphenanthrene ratio also highlighted wood combustion during forest fire outbreaks, which appeared to coincide with the past climate events.

The establishment of water quality criteria (WQC) for copper (Cu) was used as the basis for an ecological risk assessment of marine Cu pollution in Liaodong Bay, China. Published ecotoxicity data for Cu were obtained and supplemented with the results of acute Cu toxicity tests. The marine WQC for Cu in Liaodong Bay was developed using a species sensitivity distribution method with a safety factor of 2.0 and the USEPA acute-to-chronic ratio method. The ecological risk of Cu in Liaodong Bay was assessed by comparing the seawater Cu concentrations with the developed WQC. The results of this study showed that the acute and chronic Cu concentrations in Liaodong Bay were 3.31 and 2.18 μg/L, respectively. Comparison of the WQC to Cu concentrations in the bay resulted in risk quotients slightly >1.0 and typically ≤2.0. These data suggest that certain organisms in Liaodong Bay are at risk. These results can assist in the development of a pollution control management approach for the bay.