Coastal sediments in marine waters of Qatar have the potential of being contaminated by Polycyclic Aromatic Hydrocarbons (PAHs) due to extensive petroleum exploration and transportation activities within Qatar's Marine Exclusive Economic Zone. In this study, the concentration and distribution of sixteen PAHs classed as USEPA priority pollutants were measured in sediments from the eastern Qatari coast. PAHs were recovered from sediments via accelerated solvent extraction and then analyzed using Gas Chromatography–Mass Spectrometry. Total concentrations of the PAHs were in the range of 3.15–14.35μg/kg, and the spatial distribution of PAHs is evaluated in the context of sediment total organic content, depth and the grain size together with and the proximity of petroleum exploration and transportation activities. The data show that the concentrations of PAHs within the study area were in the low-range, suggesting a low risk to marine organisms and limited transfer of PAHs into the food web.

Antarctica and surrounding waters are often considered pristine, but may be subject to local pollution from tourism, fishing and governmental research programme activities. In particular, the quantification of microplastic pollution within the Antarctic Treaty area (south of latitude 60°S) has received little attention. We examined microplastic particle concentrations in sediment samples from 20 locations up to 7 km from Rothera Research Station. The highest concentrations of microplastic (<5 particles 10 ml⁻¹) were recorded in sediment collected near the station sewage treatment plant outfall. The concentrations were similar to levels recorded in shallow and deep sea marine sediments outside Antarctica. The detected microplastics had characteristics similar to those commonly produced by clothes washing. We recommend further research on microplastics around Antarctic stations to inform policy discussions and the development of appropriate management responses.

Forensic chemistry assessments documented the presence of Macondo (MC252) oil from the Deepwater Horizon (DWH) spill in offshore water samples collected under Natural Resource Damage Assessment (NRDA) protocols. In ocean depths, oiled water was sampled, observed, photographed, and tracked in dissolved oxygen (DO) and fluorometry profiles. Chemical analyses, sensor records, and observations confirmed the shifting, rising oil plume above the wellhead while smaller, less buoyant droplets were entrapped in a layer at ~1000–1400 m and advected up to 412 km southwest. Near-surface oil samples showed substantial dissolution weathering from oil droplets rising through the water column, as well as enhanced evaporative losses of lighter n-alkanes and aromatic hydrocarbons. Dispersant effects from surface applications and injected at the wellhead were seen in oil profiles as enhanced weathering patterns (increased dissolution), thus implying dispersants were a functionally effective mediation treatment. Forensic assessment methods are detailed in the Supplemental information (SI).

During the Deepwater Horizon blowout, unprecedented volumes of dispersant were applied both on the surface and at depth. Application at depth was intended to disperse the oil into smaller microdroplets that would increase biodegradation and also reduce the volumes buoyantly rising to the surface, thereby reducing surface exposures, recovery efforts, and potential stranding. In forensically examining 5300 offshore water samples for the Natural Resource Damage Assessment (NRDA) effort, profiles of deep-plume oil droplets (from filtered water samples) were compared with those also containing dispersant indicators to reveal a previously hypothesized but undocumented, accelerated dissolution of the polycyclic aromatic hydrocarbons (PAH) in the plume samples. We interpret these data in a fate-and-transport context and conclude that dispersant applications were functionally effective at depth.

Sediment geochemical characteristics were analyzed to assess how anthropogenic activities affected the Daya Bay, a subtropics bay adjacent to the most economically developed region of China. Vertical profiles of heavy metal contents and their enrichment factors indicated the development of Daya Bay environment in the past 100 years basically experienced three stages, which were closely consistent with the economic development. Before 1980s, the concentration of heavy metals was basically at the background level. Contamination of metals, particularly for Cr, Ni, Cu, Zn, Cd, and Pb, generally began in mid-1980s and became serious in 2000s. However, after late-2000s, the sediment quality had been radically improved. Heavy metals in nearshore sediment of Daya Bay were all closely related with import of anthropogenic and/or terrestrial material, whereas those in offshore were likely to be related with joint influence from the anthropogenic activities and the natural processes.

Annual rates of plastic production have been increasing rapidly since the 1950s. Inadequate or improper disposal of plastic products has contributed to a significant increase in plastic debris in the world's oceans and a corresponding increase in the number of species negatively affected by this debris. Here we investigate trends in the type, amount, and colour of ingested plastic over time, and determine whether ingested plastic contributes to reduced health of Wedge-tailed Shearwaters (Ardenna pacifica) on Lord Howe Island, Australia. The results show no clear influence of ingested plastic on body condition, while trends in the prevalence, number, and mass of plastic items ingested per bird during 2005 and 2013–2018 were more variable. There was some evidence adult birds are selecting plastic by colour. Future monitoring of this pan-tropical seabird would provide a unique opportunity to gather data from multiple sites, concurrently.

There are significant differences in the aggregation mechanisms and types of aggregates that form by oil-particle interactions in marine and laboratory environments depending on the state of oil (i.e., dissolved, emulsified, floating), size and type of particles involved (i.e., colloidal, granular, organic, inorganic), oil-particle interaction mechanisms, and settling/suspension characteristics. Distinct characteristics of oil-particle aggregates that form by interaction of granular particles with floating oil separate them from the well-known oil-colloidal particle aggregates (OcPA), which are sometimes called Pickering emulsions. Unlike OcPA, which involve emulsified oil (entrained oil droplets suspended in the water column) and colloidal particles, the oil-granular particle aggregates (OgPA) involve the floating oil and granular particles. Here, to clarify the differences and similarities between the two types of aggregates (OcPA and OgPA), we present classification of oil aggregates, drawing attention to important characteristics of OcPA, marine oil snow (MOS), and OgPA.

Water quality monitoring is important to assess changes in inland and coastal water quality. The focus of this study was to improve understanding of the spatial component of spatial-temporal water quality dynamics, particularly the spatial variability in water quality and the association between this spatial variability and catchment characteristics. A dataset of nine water quality constituents collected from 32 monitoring sites over a 11-year period (2006–2016), across the Great Barrier Reef catchments (Queensland, Australia), were evaluated by multivariate techniques. Two clusters were identified, which were strongly associated with catchment characteristics. A two-step Principal Component Analysis/Factor Analysis revealed four groupings of constituents with similar spatial pattern and allowed the key catchment characteristics affecting water quality to be determined. These findings provide a more nuanced view of spatial variations in water quality compared with previous understanding and an improved basis for water quality management to protect nearshore marine ecosystem.

This paper evaluated the total carbon stock of mangrove ecosystems in two contrasting sites: a fishing village in Delta Kelantan (DK) and Ramsar sites in Johor Park (JP). In both sites, aboveground carbon was significantly higher than belowground carbon, and stems contained more carbon than leaf and root partitions. The average carbon concentration of individual mangrove species (44.9–48.1%) was not significantly different but the larger biomass of the DK samples resulted in vegetation carbon stock that was higher than that in JP. Season played an important role in soil carbon stock—a pronounced wet season in DK coincided with the dry season in JP. The total carbon pool was estimated to be 427.88 t ha−1 in JP and 512.51 t ha−1 in DK, where at least 80% was contributed by soil carbon. The carbon dioxide equivalent was 1570.32 t ha−1 CO2e (JP) and 1880.91 t ha−1 CO2e (DK).