In 2019–2020, a mysterious oil spill reached a large part of the Brazilian coast. In order to contribute to the clarification part of these mysteries involving this accident, the present study aims to estimate the initial volume spilled using the STFM (Spill, Transport and Fate Model). We started from the hypothesis that the leak was caused by tanker buoyancy problems (hull rupture or engine failure), resulting in slow loss of part of its cargo (leaking or dumping) in the subsurface waters. The estimated volume (5000–12,500 m³) was similar to that expected in a continuous leak from an internal compartment tanker with the size between PANAMAX and SUEZMAX. This volume may have been the largest oil spill on the Brazilian coast since 2004, and it caused institutional and socioeconomic crisis because of the poor management of public resources.

The Leach's storm-petrel (Hydrobates leucorhous) is one of the most abundant and widely distributed marine birds in the North Atlantic but is under global population decline, possibly linked to marine pollution. We determined levels of ingested plastic and hepatic total mercury (THg) in recently fledged juveniles that stranded in Newfoundland and Labrador, Canada, and assessed the relationship to body condition, size and diet. Plastic prevalence was high (87.5%) but hepatic THg was relatively low (mean 486.7 ng/g dry weight) compared to other studies. Levels of neither pollutant were significantly related to body metrics of health. Our data confirm that plastic and mercury are pervasive in the western North Atlantic Ocean, prominent even in young birds.

Natural processes and human activities exert important impacts on elemental cycling in coastal sediments, which has not been well documented. Sediments in the Bohai Sea and North Yellow Sea were investigated to assess the impacts of the Yellow River inputs and/or anthropogenic perturbations on diagenesis of iron and sulfur. Labile iron (0.5 M HCl-extractable iron) in the sediments is low due to iron-poor nature of source materials. Dynamic regimes and low availability of labile organic carbon (OC) result in relatively low sulfide contents in deltaic sediments. However, low but continuous supply of labile OC exported from an anthropogenically impacted bay could substantially elevate sulfide burial in sediments near the bay. Neither offshore oil exploitations nor frequent algal blooms in the seas have detectable influences on iron and sulfur diagenesis in the sediments. The sediments are capable of quickly consuming porewater sulfide by reaction with reactive iron under the current conditions.

The Gulf of Honduras includes extensive coral reefs in Belize and Guatemala, classified into four biogeographic zones, which are differentially affected by runoff, hurricanes, and fishing. Runoff mostly impacts the coastal and adjacent channel reefs. The Belize Barrier Reef (BBR) experiences less runoff impact due to the prevailing cyclonic ocean circulation. Hurricane waves powerfully impact the BBR, only occasionally the lee-side of Glover's Reef, and rarely the coastal and channel reefs. Fishing pressure is most intense on the coastal and channel reefs, comparatively modest on the BBR, and low at Glover's Reef. The effects of the three local stressors were evaluated using observations from 24 sites in the Gulf of Honduras. Data were analyzed using the Reef Health Index (RHI), with the highest RHI (4.3) for two Glover's Reef sites, medium RHI (2.6) for 10 sites on the barrier reef, and lowest RHI (2.1) for 8 coastal reef sites.

Despite a progressive reduction of oil spills caused by the activity of maritime transportation, the latent sources of pollution still exist. Although the harmful impact of heavy fuel oil (HFO) on the marine environment is widely known, many shipwrecks cause contamination of the surrounding areas. In this paper, an approach to monitor the area of the HFO spill around a shipwreck is made using a bottom backscattering strength (BBS) obtained by a multibeam echosounder (MBES). As a case study, the s/s Stuttgart wreck located in the Gulf of Gdansk (Poland) is verified. Two different measurement campaigns have been carried out in shallow waters using low (190 kHz) and high (420 kHz) MBES frequency. The results indicate that the polluted area around s/s Stuttgart was estimated at 49.1 ha, which is around 18.3% more in comparison to the geological surveys made four years earlier.

In Chile, the toxic dinoflagellate A. catenella shows an apparent oceanic range expansion from south to the north since its first detection in 1972 in the Magallanes Region (56° S). Until 2017, A. catenella detections were restricted to a geographic area between Magallanes to Los Rios Regions (40° S). The establishment of a monitoring program in the offshore Pacific coast allowed the detection of A. catenella between 2018 and 2019 in northern areas off the Bío-Bío Region (36°S). Monoclonal cultures established from the Bío-Bío coast were genetically identified, and PSTs screened. Phylogenetic analyses determined that the Bío-Bío isolates aggregated in Group I ribotype (previously A. tamarense or A. fundyense) and the presence of PSTs analogs were confirmed. It is the northernmost detection of the toxic dinoflagellate A. catenella in the Pacific coast of Chile. These results have important implications for species monitoring and governmental management in the Bío-Bío Region.

Outdoor mesocosms with constantly flowing natural seawater were used to test the effects of littered cigarette butts on the filter feeder Mytilus edulis (blue mussel), the macroalga, Ulva lactuca (sea lettuce) and sediment microphytobenthos in a semi-natural marine setting. Either conventional, cellulose acetate, or biodegradable, cellulose, smoked cigarette butts were added at densities of 0.25 or 1 butt L⁻¹. The clearance rates of mussels exposed to 1 butt L⁻¹ of cellulose acetate butts were three times less than the controls. The growth of U. lactuca was not measurably affected by cigarette butts, however the sediment chlorophyll content was significantly less in mesocosms exposed to 0.25 and 1 butt L⁻¹ of cellulose acetate butts. These effects occurred despite constant replacement of seawater indicating how hazardous conventional cigarette butts are to marine life. Biodegradable cellulose cigarette butts had minimal effects on the measured variables but should still not be discarded as litter.

Fielding a well-trained, combat-ready military, and observing Canada's responsibility as environmental stewards are at times conflicting priorities for the Department of National Defence (DND). As new low frequency sources are introduced into service, DND must review and update policies and procedures regarding the use of active sonar to minimize its impacts on marine mammals with an evidence-based approach. Risk is mitigated primarily through avoidance, which requires an understanding of marine mammal distribution in order to avoid the most sensitive species and their habitats. In parallel, a research and development program evaluates and develops technological solutions to minimize the risk of harm. By first embracing an empirical framework to assess acute and chronic impacts, DND has been able to partner with other government departments and researchers to develop technology targeted towards the residual risks to marine mammals posed by sonar operations.

Annual monitoring was carried out in the shoreline sediments of the Calicut beach, from 2016 to 2019 to understand the distribution and abundance of microplastics and its environmental implications. Further, the impact of the severe fluvial floods of Kerala during the August months of 2018 and 2019, on the microplastic pollution of the Calicut beach was also determined. Microplastic concentrations ranged between 80.56 items/kg of dry sand to 467.13 items/kg of dry sand during the sampling period. Polyethylene type was consistently higher in all the samples. There was a surge in microplastics concentration during both the floods with a higher proportion of low-retention-period microplastics. Among the different oceanographic parameters, it was found that significant wave height and surface wind speed are positively correlated to the number of the microplastics in Calicut beach.

Human disturbance of karst landscapes in tropical volcanic islands present a unique challenge for understanding sediment transport to the coastal zone. Here we present the first evidence of urban drinking water quality impacts from industrial logging in the Solomon Islands. Despite only 6% of the Honiara's drinking water catchment being disturbed by logging, rhodamine dye tracers demonstrated complex karst sinkholes that led to high suspended sediment concentrations being transported from neighbouring Kovi catchment into the Kongulai water supply offtake point for Honiara. This has resulted in the exceedance of practical treatment thresholds of 20 NTU 9.5% of the time, leading to water supply for the majority of Honiara's residents being unavailable for 58 days in 2019. This work highlights the cost-benefit disparity between industrial logging yielding minimal short-term economic yields in comparison to on-going broader impacts of increased coastal sediment transport while restricting water supply to a developing nation's capital.