Finfish cage culture is the most predominant form of mariculture. The rapid expansion of fish cage culture systems has raised concerns about their environmental impact, such as nutrient release. In this study, for the first time, we estimated the release of nitrogen (N) and phosphorus (P) from fish cage culture in Daya Bay, southern China, by constructing N and P budget models based on a mass balance principle. In addition, the contribution and importance of nutrients from fish culture and other nutrient sources, including submarine groundwater discharge, benthic sediments, local rivers, and atmospheric deposition were assessed. The annual amount of N and P released from fish cage culture was 205.6 metric tons (hereafter tons) of N and 39.2 tons of P, including 142.7 tons of dissolved inorganic nitrogen (DIN) and 15.1 tons of dissolved inorganic phosphorus (DIP). Among the analyzed nutrient sources, the contributions of DIN and DIP from fish culture were 7.0% and 2.7%, respectively. For cages consuming conventional trash fish, 142 kg of N and 26 kg of P were released into the environment per ton of fish products, much higher than the values (72 kg N and 17.3 kg P) for cages using formulated feed. In fish culture, the dissolved nutrients were more N rich, but the particulate nutrients were more P rich. The ratio of cage-derived N and P was 21.1, higher than the ratio of coastal seawater (27.1), indicating that cage culture may also impact the local nutrient forms around farming regions. Oyster cultivation and harvest removed 126.3 tons of N and 35.1 tons of P from of the bay. Replacing trash fish with formulated feed and co-culturing of nutrient extractive species (e.g., bivalves, macroalgae) and deposit-feeding species (e.g., sea cucumber) in fish culture zones can be efficient nutrient mitigation strategies.

Concentration of organochlorine pesticides (OCPs) (α-, β-, γ- hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE)) in four species of Pacific salmon (pink, chum, chinook, and sockeye) are presented. OCPs in salmon organs increased in the following order: muscle < liver < eggs < male gonads. Concentrations of the OCP in salmon organs increased in following order: DDE < γ-HCH < α-HCH. The level of pollutants in salmon is compared with the sanitary and epidemiological norms of Russia and other countries. Cancer and noncancer hazard ratios through consumption of salmon in Russian Far East for both men and women also were summarized. Noncancer and cancer hazard ratio values were far below threshold values (<1.0).

Zooplankton assembly was characterized during the spring tide near a submarine outfall that discharges raw sewage directly into the southeastern portion of Guanabara Bay, near the Niterói, a highly urbanized center. The rain period directly influences water surface temperature and salinity, as has been previously observed in this bay. Dissolved oxygen (DO) and biochemical oxygen demand (BOD) were within the concentrations stipulated by the Brazilian legislation. The low chlorophyll a values observed herein may be associated with a nutritional imbalance to which phytoplankton may be subjected, observed through the carotenoid/chlorophyll ratio, which probably reflects zooplankton community composition. Twenty major zooplanktonic taxonomic groups were recorded, with a predominance of holoplanktonic taxa, mainly copepods. Mean zooplankton density and composition were in agreement with other studies in the region, however, these community characteristics at each of the sampling stations appear to be related to the urbanization degrees of each Niterói neighborhood.

Plastics in the ocean are of great concern nowadays, and are often referred to as the apocalyptic twin of climate change in terms of public fear and the problems they pose to the aquatic and terrestrial environment. The number of studies focusing on the ecological effects and toxicity of plastics has substantially increased in the last few years. Considering the current trends in the anthropogenic activities, the amount of plastics entering the world oceans is increasing exponentially, but the oceans have a low assimilative capacity for plastics and the near-surface layer of it is a finite space. If loading of the oceans with plastics continues at the current rate, the thin sea surface microlayer can have a substantial amount of plastics comparable to the distribution of phytoplankton, at least in the major oceanic gyres and coastal waters in the future. Also, processes like biofouling can cluster microplastics in dense fields in the near-surface layer. Plastics can contribute to the warming or cooling of the water column by scattering and attenuating incoming solar radiation, leading to a potential change in the optical and other physico-chemical properties of the water column. We propose a new notion that changes in solar radiation in the water column due to the plastics have the potential to affect the physical processes in the ocean surface and near-surface layers, and can induce climate feedback cycles. The future can be very different, if plastics evolve as one of the key players affecting the ocean physical processes and hence this is the time to tackle this puzzle with appropriate strategies or let the genie out of the bottle.

This study investigated the network of polycyclic aromatic hydrocarbon (PAH) degraders in the Yangtze estuarine and coastal areas. Along the estuarine gradients, Proteobacteria and Bacteroidetes were the dominant bacterial phyla, and forty-six potential PAH degraders were identified. The abundance of genes encoding the alpha subunit of the PAH-ring hydroxylating dioxygenases (PAH-RHDα) of gram-negative bacteria ranged from 5.5 × 10⁵ to 5.8 × 10⁷ copies g⁻¹, while that of gram-positive bacteria ranged from 1.3 × 10⁵ to 2.0 × 10⁷ copies g⁻¹. The PAH-degraders could represent up to 0.2% of the total bacterial community and mainly respond to PAHs and Cu concentrations, which indicate anthropogenic activities. Salinity and pH showed negative regulating effects on the PAH-degrading potential and the tolerance of bacteria to pollutants. PAH degraders such as Novosphingobium and Mycobacterium exhibit heavy-metal tolerance and core roles in the network of PAH degraders. These outcomes have important implications for bioremediation.

Recent technology developments have turned present-day unmanned systems into realistic alternatives to traditional marine animal survey methods. Benefits include longer survey durations, improved mission safety, mission repeatability, and reduced operational costs. We review the present status of unmanned vehicles suitable for marine animal monitoring conducted in relation to industrial offshore activities, highlighting which systems are suitable for three main monitoring types: population, mitigation, and focal animal monitoring. We describe the technical requirements for each of these monitoring types and discuss the operational aspects. The selection of a specific sensor/platform combination depends critically on the target species and its behaviour. The technical specifications of unmanned platforms and sensors also need to be selected based on the surrounding conditions of a particular offshore project, such as the area of interest, the survey requirements and operational constraints.

Since 2011, tropical beaches from Africa to Brazil, Central America, and the Caribbean have been inundated by tons of sargassum seaweed from a new equatorial source of pelagic sargassum in the Atlantic. In recent years the extraordinary accumulations of sargassum make this a nuisance algal bloom for tropical coasts. In 2018 satellite data indicated floating mats of sargassum that extended throughout the Caribbean to the northeast coast of Brazil with the highest percent coverage over the water yet recorded. A literature review suggests that Atlantic equatorial recirculation of seaweed mats combined with nutrients from several possible sources may be stimulating the growth and accumulations of sargassum. In the western equatorial recirculation area, new nutrient sources may include Amazon River floods and hurricanes; in the eastern equatorial recirculation area, nutrient sources that could sustain the sargassum blooms include coastal upwelling and Congo River freshwater and nutrients.

The bioturbation potential of macrobenthos communities (BPc) is an important parameter in marine ecology. Based on macrobenthos field surveys, BPc values were estimated in Bohai Bay, China. The horizontal distribution of BPc values changed across seasons while showing a certain level of continuity over time. The maximum BPc value was recorded in summer while the minimum occurred in winter. Although only a few environmental variables showed a statistically significant (p < 0.05) correlation with BPc, about 20 environmental variables exhibited a moderate correlation with BPc (0.3 < r < 0.5). The depth of the redox potential discontinuity (RPD) measured in situ changed across seasons, and the biogenic mixing depth values derived from the BPc index exhibited a relationship with the lowest RPD depth measurements. Our results suggest that the RPD depth can be predicted from BPc values, thereby showcasing a useful application of the BPc index in marine benthic pollution and environmental management research.

The impact of ghost fishing in large coastal ecosystems has generated considerable interest. In smaller, understudied systems with fewer stakeholders, derelict fishing gear (DFGs) may have impacts similar to these larger systems at the same relative scale. Four years of side scan sonar surveys in the Mullica River-Great Bay Estuary (New Jersey, USA) supported the recovery of 1776 DFGs off-season by commercial partners. Locations with high densities of recovered DFGs (>200 DFGs/km²) occupied intersections of recreational vessel traffic and commercial crabbing activity. Condition and depth-in-sediment of recovered DFGs was used to evaluate true bycatch (terrapins, whelks, blue crabs) versus species utilizing degraded gear as habitat (juvenile tautog, oyster toadfish). Critically, gear recovered in-season with low cost sonars (an additional 225 DFGs) prevented the accumulation of new DFGs which likely generate the highest percentages of bycatch. Removal of DFGs in this system led to significant ecological (reduced bycatch), economic (>$61,000 in direct pay, reused gear), and anticipated future benefits (increased harvest).