The influence of sedimentary metals on the cockle A. trapezia tissue was examined using a strong difference in sedimentary metal concentrations in an embayment (Hen and Chicken Bay) highly contaminated in Cu and an adjacent cove (Iron Cove), strongly enriched in Cd, Cu, Pb and Zn within the heavily-urbanised Sydney estuary catchment (Australia). Statistically significant differences were recorded for cockle tissue metal concentrations between the study locations reflecting differences in surficial sediment metal concentrations. Low metal uptake was apparent in A. trapezia tissue, which were considerably less than background sedimentary concentrations and was of low-risk for human consumption. Dissimilar bioconcentration of Cd, Cu, Pb and Zn was apparent in tissue of cockles (A. trapezia), prawns (Metapenaeus bennettae), mussels (Mytilus galloprovincialis) and oysters (Saccostrea glomerata), due possibly to different feeding patterns and biogeochemical conditions in bottom sediments.

Microplastic pollution has gained significant attention, and there are growing concerns about its potential effects on aquatic environments. The lack of proper solid waste management in Egypt has resulted in the accumulation of plastic litter and its deposition in waterways. However, no attempts have been made to identify or assess marine plastic litter in Egypt. We provide, for the first time, a precise, simple, and cost-effective method to identify microplastics in Eastern Harbor by using differential scanning calorimetry (DSC). This screening revealed the presence of ten polymers in seawater and shoreline sediments. Most of the extracted microplastics are secondary microplastics, as they appear to be remnants of larger plastic fragments.

Hydrocarbonoclastic bacterial consortium that utilizes crude oil as carbon and energy source was isolated from marine sediment collected at a depth of 2100 m. Molecular characterization by 16S rRNA gene sequences confirmed that these isolates as Oceanobacillus sp., Nesiotobacter sp., Ruegeria sp., Photobacterium sp., Enterobacter sp., Haererehalobacter sp., Exiguobacterium sp., Acinetobacter sp. and Pseudoalteromonas sp. Self-immobilized consortium degraded more than 85% of total hydrocarbons after 10 days of incubation with 1% (v/v) of crude oil and 0.05% (v/v) of Tween 80 (non-ionic surfactant) at 28 ± 2 °C. The addition of nitrogen and phosphorus sources separately i.e. 0.1% (v/v) of CO (NH₂)₂ or K₂HPO₄ enhanced the hydrocarbon utilization percentage. The pathways of microbial degradation of hydrocarbons were confirmed by FTIR, GC–MS, ¹H and ¹³C NMR spectroscopy analyses. These results demonstrated a novel approach using hydrocarbonoclastic self-immobilized deep sea bacterial consortium for eco-friendly bioremediation.

Microplastics (MPs) are widespread and cause many impacts, yet their distribution and abundance are unknown for the Amazon coast. We estimated the abundance and distribution of microplastics at a sandy beach on the northern Brazilian coast during April 2014. Sand was collected and analyzed at three depth strata (0–20, 20–40 and 40–60 cm). MPs (250–500, 501–5000 μm) from each depth were sieved and retrieved by flotation when necessary. We found 492.5 ± 556.4 particles m⁻³, with fibers comprising up to 95%. The abundance decreased with depth (61.5, 25 and 13.5% from the surface to 40–60 cm) and the deposition zone showed higher densities compared to the erosion zone. Although present in low to moderate abundance, MPs were widespread on the beach. The Amazon coast is an important area for fisheries and traditional communities, and further studies of its potential as a source or sink of MPs are needed.

With the status as the world's top contributor of marine plastic debris, Indonesia has committed to reduce marine plastic debris up to 70% in 2025 by establishing the National Action Plan (NAP) on Marine Debris. The high amount of marine plastic debris as a result of transport and accumulation become a complex issue in Indonesia due to its ocean-atmospheric circulation, high population of coastal communities, and marine activities. Based on our findings, there are gap of publications related to marine debris in Indonesia that had been already published. Marine debris is ubiquitous and transboundary, as they were found in marine environment and transported by currents to various direction including uninhabited islands, thus, we propose more comprehensive future research about the impact of marine debris on ecosystem (e.g. biological impact of organisms in the water column, ecological alteration in distribution pattern, and invasive species), human health, and economic loss.

Methods standardisation in microplastics research is needed. Apart from reagent-dependent effects on microplastics, varying target particle sizes can hinder result comparison between studies. Human health concerns warrant recovery of small microplastics. We compared existing techniques using hydrogen peroxide, Proteinase-K, Trypsin and potassium hydroxide to digest bivalve tissue. Filterability, digestion efficacy, recoverability of microplastics and subsequent polymer identification using Raman spectroscopy and a matching software were assessed. Only KOH allowed filtration at ≤25 μm. When adding a neutralisation step prior to filtration, KOH digestates were filterable using 1.2-μm filters. Digestion efficacies were >95.0% for oysters, but lower for clams. KOH destroyed rayon at 60 °C but not at 40 °C. Acrylic fibre identification was affected due to changes in Raman spectra peaks. Despite those effects, we recommend KOH as the most viable extraction method for exposure risk studies, due to microplastics recovery from bivalve tissues of single-digit micrometre size.

Sediments of Yellow Sea dumping sites (YSDS) collected in 2015 were analyzed using the European Community Bureau of Reference (BCR) sequential extraction method to assess the contamination and potential risk to the environment. Cr, Ni, Cu, and Zn exhibited the most dominant residual fraction, whereas Cd was mostly in the exchangeable fraction and Pb in the reducible fraction. Cr contains a significant amount of oxidizable fraction in the dumping area due to the dumping of tannery sludge with high concentrations of Cr, mainly in the organic matter-bound form. The global contamination factor (GCF) showed that high non-residual fractions of Cd and Pb contributed considerably to contamination. Nevertheless, modified potential ecological risk index (MRI) suggested low ecological risk for metals in YSDS because of the low total content of Cd and the small mobile fraction of other metals.

With the recovery of whale populations, carcass strandings on beaches are growing. Beach burial is a common management option for stranded carcasses. However, communities fear shark attraction following leachate transport to the ocean via submarine groundwater discharge. Here, a sediment column mesocosm experiment indicated that carcasses can be a localised source of dissolved organic carbon (DOC), phosphate and ammonium to groundwater. The spatial reach of the leachate plume was <2.5 m, while the temporal stabilisation occurred over 100–300 days. No significant chemical signals were observed under a beach-buried carcass, implying effective attenuation of decomposition plumes. For beaches with conditions similar to our one-directional, fast-flowing sediment experiment generating extreme groundwater contamination, it is unlikely that any leachate from a whale carcass would reach the ocean if buried >25 m onshore. Therefore, carcass leachate plumes would only potentially attract sharks to the surf under specific conditions not experienced during our experiments.

The 90Sr activities of seawater were investigated in the high-latitude region of the Arctic Ocean from August–September 2017. The 90Sr activities in seawater in the Chukchi Sea, central Arctic Ocean and East Greenland Sea were 0.31–2.42, 0.12–1.86 and 0.13–1.20 Bq m−3, respectively. The average 90Sr activity (0.92 Bq m−3) below 500 m in the central Arctic Ocean was higher than those in previous reports. Our study provided high-resolution baseline 90Sr activity data for the whole water column in the high-latitude region of the Arctic Ocean (~85°N). The inventory of 90Sr in the central Arctic Ocean was higher than those in the Chukchi Sea and East Greenland Sea. The results of our study indicated that 90Sr could be transported to the deep seawater and remain in the Arctic Ocean for a long time.

The northeastern Arabian Sea (NEAS) experiences convective mixing during winter, but this mixing does not reach up to the silicicline, resulting in the limited supply of silicate (Si) compared to nitrate (N) and phosphate (P) to the mixed layer (ML) and formation of non-diatom blooms. The poleward advection of waters of low surface salinity by the West India Coastal Current (WICC) to the NEAS weakens the vertical mixing and reduces the Si input to the mixed layer, resulting in occurrence of Noctiluca scintillans blooms. The saturation of dissolved oxygen in the NEAS varied between 88 and 98%, suggesting N. scintillans blooms occur in oxic conditions. Enhanced cell abundance of N. scintillans was observed in the bloom region in the upper 10 m. Phytoplankton pigments data revealed higher contribution of Chlorophytes, Prasinophytes, Prymnesiophytes and Prochlorophytes in the bloom than non-bloom region. The isotopic composition of nitrogen and carbon of particulate organic matter indicated that natural and in situ processes contributed to both nutrients and organic carbon pool in the NEAS in supporting the massive occurrence of N. scintillans blooms than hitherto hypothesized to anthropogenic sources. This study further suggests that the effect of anthropogenic pollutants released into the NEAS from the mega-cities is limited to the neighbourhood of these cities and does not affect the open ocean.