Port environments are highly dynamic and hotspots for marine bioinvasion. This study investigated the bacterial diversity at two geographically distant ports (Mangalore-marine port; and Haldia-riverine port) using next-generation sequencing during southwest monsoon and non-monsoon (Pre-monsoon) seasons. During southwest monsoon, at both marine and riverine ports, operational taxonomic units (OTUs) affiliated to bacteria reported to have hydrocarbon degrading ability were observed. Whereas during pre-monsoon, a significant increase in benthic bacterial OTUs was evident at the marine port, and the riverine port was characterized by oceanic species OTUs. Results suggest that the dynamics of prevalent environmental conditions, driven by seasons, led to emergence of ecologically relevant bacteria, many of which have been observed for the first time in Indian coastal waters. Their presence could be used as indicators of prevailing environmental conditions and nature of anthropogenic influence in port ecosystems. Unravelling functional roles of such ecologically relevant species is a way forward.

Given the increase in plastic production, persistence, and toxicity in the environment, understanding the probability of microplastics (MPs) accumulation in the sediments of the rivers' estuary is urgently needed. In this study, sediments of the estuary of 17 rivers, ending to the Caspian Sea, were evaluated at two depths (0–5 cm and 5–15 cm). Plastic particles were categorized into two groups in terms of size: small MPs and large MPs. The combination of observational techniques, FTIR, and SEM analysis was applied to identify MPs. The mean of MPs in 17 rivers was obtained at a depth of 0 to 15 cm of sediments 350.6 ± 232.6 MP/kg. The fiber was identified as the predominant particles in sediments, and foam-shaped particles were the least amount in the sediment. In terms of polymer structure, polyethylene (PE) (20%) and polyvinyl chloride (PVC) (2%) showed the highest and lowest prevalence, respectively. In the current study, the number of MPs was higher than the average of MPs in sediments of recreational-tourist areas and non-tourist areas of the southern Caspian coast. Results from this study indicate that sediments of the rivers' estuary are a hotspot of plastic particle pollution. Therefore, plastic management in the path of the Caspian catchment area of Iran, and cleaning rivers coast and rivers mouth from plastic is recommended.

Anthropogenic activities experienced a pause due to the nationwide lockdown, imposed to contain the rapid spread of COVID-19 in the third week of March 2020. The impacts of suspension of industrial activities, vehicular transport and other businesses for three months (25 March-30 June) on the environmental settings of Chennai, a coastal megacity was assessed. A significant reduction in the key urban air pollutants [PM₂.₅ (66.5%), PM₁₀ (39.5%), NO₂ (94.1%), CO (29%), O₃ (45.3%)] was recorded as an immediate consequence of the reduced anthropogenic activities. Comparison of water quality of an urban river Adyar, between pre-lockdown and lockdown, showed a substantial drop in the dissolved inorganic N (47%) and suspended particulate matter (41%) during the latter period. During the pandemic, biomedical wastes in India showed an overall surge of 17%, which were predominantly plastic. FTIR-ATR analysis confirmed the polymers such as polypropylene (25.4%) and polyester (15.4%) in the personal protective equipment.

The use of dispersants can be an effective response tool for large offshore spills by applying dispersants on unemulsified slicks and treating as much oil as possible before it becomes too viscous. Assessing the dispersibility of an oil slick under actual environmental conditions is an important step in spill response decision-making. This research seeks to develop a new field kit that is quick and reliable and could be used by spill response personnel without scientific training. The resulting Dispersibility Assessment Kit (DAK) incorporates an automated mixing unit to standardize the applied energy, thereby eliminating the variability in “hand mixing” that is used in other dispersant field kits. The automated mixing energy was studied to determine the optimal mixing regime that correlates with ocean conditions and was incorporated in the DAK protocol. The DAK was validated against 14 oils and emulsions and was successfully tested by response personnel during at-sea demonstration.

This is the first investigation of the potential for using Cymodocea nodosa to biomonitor trace element (TE) contamination in Marchica lagoon (Morocco), a Mediterranean pollution hotspot. We measured concentrations of seven TEs in seagrass tissues (leaf-rhizome-root) and sediments. Single and multi-element indices confirmed that sediments near illegal discharges were heavily polluted and we predicted risks of frequent adverse biological effects in these areas. Four of the TEs increased concentrations in C. nodosa leaf and root along sediment pollution gradient. Leaves and roots were both good indicators of Cu and Cd contamination in sediment, whereas leaves were the best indicator of Zn and roots for Pb. This seagrass was not a bioindicator of Al, Cr and Ni contamination. These results show the bioaccumulation patterns of TEs in C. nodosa, and can be used to design biomonitoring programs.

The 2010 Deepwater Horizon (DWH) oil spill affected nearly 1105 km of coastal marsh. Long-term shoreline loss in the northern Gulf of Mexico is an important question with far-reaching ecological and human-use implications. Numerous studies have examined potential exacerbated marsh shoreline retreat after the DWH using ground-level sampling and/or aerial/satellite imagery interpretation. This paper reviews previous DWH erosion studies, discusses their limitations and sometimes conflicting results, and provides a comprehensive analysis of a larger data set. Shoreline retreat measurements from multiple studies following the DWH incident were combined for 131 herbaceous marsh sample sites for the period from Fall 2010 to Summer 2015. Significant increases in shoreline loss were found only in the period from Fall 2010 to Fall 2011 for heavily oiled shorelines relative to other periods. The evidence does not suggest widespread long-term coastal marsh erosion from the DWH.

Three cruises were conducted during an Ulva prolifera bloom in 2018 off the Qingdao coast to observe early-, late-, and after-bloom characteristics. Spatio-temporal changes in dimethylsulfide (DMS), dimethylsulphoniopropionate (DMSP), and acrylic acid (AA) and their relationships with environmental parameters were examined. Mesocosm experiments tested the effect of nutrient on the release of biogenic sulfur compounds during the decline period. Biogenic sulfur concentrations contrasted with those in non-bloom regions and reached their highest values during the late-bloom period. The average sea-to-air DMS flux was about 5 times higher than those of non-bloom regions. The mean concentrations of DMS and DMSP in the enclosures were 3–5 times those of in-situ seawater. Biogenic sulfur release was promoted by the addition of high concentrations of nutrients as U. prolifera was declining. The contribution of the U. prolifera bloom to atmospheric DMS was estimated to be 125 kg S d⁻¹.

The focus of this study was to determine the depth-wise variability of physicochemical properties (i.e., pH, TOC, TN, and EC), and heavy metals (i.e., Pb, Cu, Zn, As, and Cr) concentration, and the associated biological and ecological risks of the mangrove sediment. The accumulation of metal contents and the phytoremediation and phytoextraction were also investigated in a mangrove species, Acanthus ilicifolius. The mangrove sediment consists of a higher proportion of sand fraction (56.6–74.7%) followed by clay (10–28%) and silt (10.1–15. 7%) fractions. The concentrations (mg/kg) of Pb, Cu, Zn, As, and Cr were ranged from 22.05–34.3, 8.58–22.77, 85.07–114, 5.56–12.91, and 0.98–5.12 in all the sediment layers. The hierarchy of the mean metal concentration in sediment was Zn (102 mg/kg) > Pb (25.6 mg/kg) > Cu (14.8 mg/kg) > As (8.79 mg/kg) > Cr (2.74 mg/kg) respectively. The examined metal concentrations were below the respective average shale values (ASVs). The degree of environmental, ecological, and biological risks was minimal according to various pollution indices like geoaccumulation index (Igₑₒ), contamination factor (CF), and pollution load index (PLI). According to sediment quality guidelines (SQGs), the adverse biological risk effect was not likely to occur. The result of the potential ecological risk index (PERI) demonstrated that the study area was in the low-risk condition as the corresponded RI value < 100. A combined influence of geogenic and anthropogenic factors was identified as the metal sources by multivariate analysis. The study found that the accumulation rate of the metal contents was higher in leaves than that of roots. The mean descending metal concentration values were Zn (107) > Pb (28. 7) > Cu (16.9) > As (11.2) > Cr (4.99) in leaves and Zn (104.32) > Pb (27.02) > Cu (15.29) > As (10.39) > Cr (3.80) in roots. The translocation and bioaccumulation factors of heavy metals suggested that the mangrove plant species, A. ilicifolius can be used for phytoremediation and phytoextraction since the bio-concentration factor and translocation factor > 1. The studied species exhibited the metal tolerance associated with two following strategies, metal exclusion, and metal accumulation. However, excess metal tolerance can impact the surrounding marine environment.

Elemental profiles in seawater, sediment and green-lipped mussels (Perna canaliculus) were determined, following the deposition of earthquake demolition rubble into a newly developed sea-fill located adjacent to a busy commercial port with a history of diverse contaminant inputs. Zinc and lead displayed environmental concentrations that varied over time during sea-fill construction, and which declined with distance from the sea-fill, indicating that the sea-fill activity was the source of these two contaminants. A transplantation study using reference site mussels caged near the sea-fill, supported this finding. However, none of the trace metal burdens in resident or transplanted mussels were of regulatory concern. An integrated approach comprising the monitoring of multiple environmental matrices, examination of contaminant burdens as a function of time and distance from a putative point source, and the use of active biomonitoring techniques, is necessary to robustly identify novel contamination inputs in historically-polluted marine settings.

Following accidental release into marine environments, crude oil progressively weathers, influencing composition, fate, and toxicity. However, published studies draw conflicting conclusions on the effects of oil weathering on ecotoxicity. Using the PETROTOX model, this study characterized the effect of weathering on acute oil toxicity for four aquatic species. Results indicated that predicted acute toxicity decreased with increased oil weathering, due to reductions in overall concentrations and bioavailability of hydrocarbon constituents.