Mid-ocean ballast water exchange (BWE) is recommended for international vessels to minimize the transfer of nonindigenous species (NIS). When this cannot be accomplished due to safety concerns, alternate ballast water exchange zones (ABWEZ) may be used. A coupled-ice-ocean model with meteorological forcing and particle tracking was used to evaluate the relative risks from BWE along primary shipping routes into Canada's eastern Arctic. Relative risk to receiving habitats from BWE was calculated from the product of likelihood of exposure, likelihood of establishment, and habitat sensitivity to potential NIS. Modelling results indicate that existing ABWEZs in and around Lancaster Sound and Hudson Strait are among the areas of highest relative risk for introductions of NIS via ballast water. The deeper offshore regions of Labrador Sea and Baffin Bay should be considered as alternatives. However, further research is recommended to assess the risks of NIS associated with BWE in the Canadian Arctic.

Surface sediments were collected from the shore and lagoons of Kavaratti, Kadmat and Agatti islands of Lakshadweep Archipelago and analysed for trace element concentration. The sediment contamination was assessed on the basis of geochemical, biological hazard and ecological risk indices. Except Cd and Pb, all the other trace elements selected for the study were below the contamination level. Compared to Kadmat, Kavaratti and Agatti were more polluted and the pollution was pronounced in lagoons than shore. Population pressure, untreated sewage, diesel based power generation, shipping and tourism activities contribute to sediment contamination. Statistical analysis revealed the association of trace elements with sedimentary characteristics due to anthropogenic sources.

In this study, positive matrix factorization, multilinear engine 2, and geographic information systems were used to characterize the spatial-temporal patterns of sources for nine heavy metals in the surface sediments of the Yangtze River Estuary in different seasons. Results showed that six sources were identified: agricultural pesticide, marine transportation, chemical factory wastewater, metal smelter waste, atmospheric deposition, and agricultural fertilizer. The proportions of sources were similar during the entire year but varied among the seasons. The differences in the proportions of agricultural pesticide between winter and other seasons were greater than 12%. Over 40% of the Cd concentration in most seasons was attributed to atmospheric deposition, while less than 5% in autumn. The impact strength of most sources, except marine transportation and metal smelter waste, decreased from the inner regions to the adjacent sea. The difference in the impact strength of agricultural pesticide was the largest throughout the study area.

Metal contamination in fish is a concern worldwide, including in the Arabian/Persian Gulf region. This review summarizes the findings from 55 papers about metal concentrations in Gulf fish. Metal concentrations in muscle tissue were screened against the most recent maximum allowable levels (MALs) for fish in international commerce. We identified metals, fish species, and locations where concentrations exceeded the MALs. For some metals, recent MALs have been set to lower concentrations as more toxicological data have become available. Mean fish tissue concentrations exceeded the MAL in 13% (arsenic), 76% (cadmium), 56% (lead), and 10% (mercury) of species means. We identified 13 fish species with the potential to serve as bioindicators of metal contamination for use in four Gulf habitats: pelagic, benthopelagic, demersal, and coral reefs. Recommendations are provided for a regional approach to improve consistency of sampling, data analysis and reporting of metal concentrations in Gulf fish.

Nutrients distribution and influencing factors in three seamount areas named Y3, M2 and C4 of the Tropical Western Pacific Ocean (TWPO) were investigated. Nutrients showed obvious uplifts around the three seamounts, consistent with the uplifts of isotherms and isohalines, indicating the existence of a bottom-up process of nutrients. Meanwhile, compared with the stations away from seamount and the reference stations in the TWPO, nutrients concentrations around seamount were much higher. Among the three seamounts, the average nutrients concentrations were highest in Y3, while they were lowest in C4. Moreover, compared with the obvious nitrogen limitation in Y3 and M2, the N:P (13.5:1) and Si:N (6.1:1) were closed to the Redfield ratio. The current-seamount interaction was the determining influencing factor on nutrients distribution, causing the hydrology dynamic changes such as uplifts and Taylor column. Meanwhile, T and S also affected nutrients distribution, especially nutrients and T showed significant negative correlations.

An Eulerian passive tracer model coupled with a quadruple-nested 3D circulation model was used to assess the coastal dispersal of treated wastewater effluent from a sewage treatment plant and the associated impacts on an adjacent seaweed farm using three different operational scenarios. When the discharged volume and source effluent fluxes were decreased by ~16.7%, the accumulated effluent in the farm was reduced by ~25.4%. A tracer flux budget analysis revealed the apparent predominance of the transient component that accounts for the nonlinear interactions primarily from tidal currents and eddies. The transient flux promoted the effluent influx to impede effluent accumulation in the farm, whereas the mean flux contributed to the outgoing flux. A source flux reduction caused a remarkable decrease in the transient flux and thus an even greater effluent accumulation reduction. In turn, a modified source density scenario without total effluent volume change did not work as expected.

Surface sediments (n = 35) and a core sample around Pars Special Economic Energy Zone were analyzed to address spatiotemporal variations of heavy metals. Enrichment factors classified the elements as: (1) poorly enriched, geogenic elements (Co, Cr, Fe, Li, Mn, Mo, Ni, Ti, and V), (2) minimal enriched elements (Zn and Mg), (3) moderately enriched elements (Ag, Cd, Pb, Se, and Sr), and (4) significantly enriched element (As and Hg). The core profile showed that As, Hg, Ag, and Cd had considerable anthropogenic inventories. Arsenic levels were continuously increasing toward the top of the core and sedimentary cycling was not an effective factor on its enrichment. Pollution load index classified the area as a severely affected region and Risk Index values suggested that 57% of the sediments had a moderate potential risks. The mapping techniques proposed a polluted and hazardous patch at the entrance and center part of the Nayband Bay.

The toxic equivalences (TEQs) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) from sediment of aquatic systems in Durban, South Africa were determined in two ways: 1) TEQs of PAHs and PCBs were determined by instrumental analyses and converted to 2,3,7,8‑tetrachlorodibenzo‑para‑dioxin equivalence (TCDDeq). 2) Bioassay equivalences (BEQs) of aryl hydrocarbon receptor (AhR) ligands were analysed using the H4IIE-luc bioassay. TEQs of PCBs ranged from below limit of detection (<LOD) to 57 pg TCDDeq·g⁻¹ while PAHs ranged from <LOD to 790 pg TCDDeq·g⁻¹. BEQs were 100- to 1000-fold greater than TEQs. Potency-balance revealed <10% of the BEQs were explained by instrumentally analysed compounds. Sediment quality guidelines indicated di minimis risk relating to TEQs, however had potential risk due to BEQs. The results reveal that far more AhR ligands were present in the sediments than what was instrumentally analysed and capable of causing AhR-mediated toxicity.

Seagrass meadows are declining at alarming rates globally due to both anthropogenic activities and natural threats. Seagrasses play key ecological roles in coastal ecosystems as primary producers and providers of habitat and environmental structure. Therefore, mapping seagrass beds is indispensable for the effective monitoring and management of coastal vegetated habitats. In contrast to direct sampling techniques and optical remote sensing, active hydroacoustic techniques are relatively inexpensive and efficient for the detection of seagrass. We used a single beam echosounder to detect the spatial and temporal distribution characteristics of the eelgrass Zostera marina L. in an important overwintering habitat for the whooper swan Cygnus cygnus (Swan-Lake lagoon), northern China. We also distinguished echograms of the macroalgae Chaetomorpha linum K. and outlined its threat to seagrass. We also propose a method for calculating the accuracy of interpolation analyses. Results showed that: (1) The distribution of seagrass in Swan Lake varies with seasons, with maximum distribution area in summer. The maximum distribution area of seagrass beds in Swan Lake was 199.09 ha–231.67 ha, accounting for 41.48%–48.26% of the area of Swan Lake; (2) C. linum is a growing threat for seagrass beds of Swan-lake, with distribution area as high as 129.28 ha in May 2018. The invasion and competition by C. linum against seagrass beds could be one of the reasons for the decline in seagrass beds in Swan-Lake; (3) Topo to Raster has the highest interpolation accuracy and is the most conservative among three interpolation methods. Topo to Raster was the most suitable interpolation method for the sonar detection of seagrass beds. The findings may facilitate the application of sonar technology in seagrass monitoring and provide data for the formulation of appropriate seagrass bed management and restoration strategies and policies.

In this article we compare the efficiency of different methods of rapid-response remediation of beach sand contaminated with microbiological and/or organic matter. Contaminated beach sands were treated in laboratory by different treatment methods (i.e., oxidation, UV-photoexposure, or thermal methods) and the efficiency of disinfection and breakdown of organic matter were evaluated. Contaminants in raw and treated beach sands were measured by membrane filtration method, and by chemical and biochemical oxygen demand, and chromatographic analysis. All the methods tested were efficient for disinfecting beach sand with microbiological contamination, except for the UV-photoexposure method, which showed only moderate disinfection potential. Chemical degradation efficiency of beach sand contaminated by crude petroleum was higher with Fenton and Photo-Fenton (associated with the use of surfactant and ultrasound) methods. Photo-Fenton method improvement can increase the efficiency of contaminated beach sand treatment, and can also help beach managers when selecting which method to adopt for remedial actions.