Ecosystem based water quality models are important tools for prognostic site assessment and evaluation of ecosystem-performance of marine fish farms. We present the development and application of a comprehensive Fish Culture Zone Water Quality Model using continuous bi-weekly field data over a six-year period (2012–2017). The model simulates five interacting subsystems: phytoplankton, phosphorus and nitrogen cycles, and the dissolved oxygen (DO) and particulate organic carbon balance. The application of the model to two fish culture zones in Hong Kong shows the model captures the trends of nutrient and DO variation and the performance in quantitative prediction of algal biomass is challenging. The effect of errors in the specification of primary model inputs are evaluated using dimensionless sensitivity coefficients based on First Order Variance Analysis reveals the relative importance of fish stock (loading), physical size (volume), tidal flushing rate and boundary conditions in the prediction of key water quality variables.

Microplastics (MPs) in soil and sediment (SS) matrices are emerging pollution hazards to ecosystems and humans. To mitigate MP pollution, suitable extractors and associated extracting solutions are required to efficiently separate MPs from SS matrices. In this study, we introduced a four-stage microplastic extractor (ME) device and investigated the fractional separation efficiencies of three extracting solutions (ultrapure water, saturated NaCl, and corn oil-in-NaCl) plus aeration, magnetic stirring, and electric stirring for three kinds of SS matrices (loam soil, sandy sediment, and muddy sediment) with four types of virgin MP pellets (acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polypropylene, and polystyrene). In addition, fragments of these four types of post-consumer MPs were also tested by the ME device. The mean recovery efficiencies of these MPs in the three SS matrices were 88.3 %–100 %. Oil-in-NaCl further improved the recovery efficiencies for the denser ABS and PC up to 40 % based on NaCl extraction.

Aquaculture, also known as aqua farming, is defined as farming fish, crustaceans, mollusks, aquatic plants, algae, and other marine organisms. It includes cultivating fresh- and saltwater populations under controlled conditions compared to commercial fishing or wild fish harvesting. Worldwide, carp, salmon, tilapia, and catfish are the most common fish species used in fish farming in descending order. Disinfectants prevent and/or treat different infections in aquatic animals. The current review indicates the uses of different disinfectants against some important pathogens in aquaculture, with particular reference to tilapia (Oreochromis niloticus) farming. A single review cannot cover all aspects of disinfection throughout aquaculture, so the procedures and principles of disinfection in tilapia farming/aquaculture have been chosen for illustration purposes.

The eastern part of the Bay of Seine (English Channel) is highly impacted by harbour activities and the dumping of dredged sediment by the port authorities of Le Havre (GPMH) and Rouen (GPMR). Sediment dredged by the GPMH (2–2.5 millions of m³ per year) has been disposed at the subtidal Octeville site since 1947. Since the 2000s, mainly fine sediment (80% of fine particles <63 μm) has been disposed using alternate mosaic boxes with limited thickness (0.2 to 0.6 m per box per year), preventing the accumulation of disposed sediment in some parts of the dumping site. During the period August 2016 to September 2017, an experimental study was set up to identify the spatio-temporal changes of the macrobenthos collected at ten stations on six dates: three stations where different volumes of sediments were dumped (from 41,000 to 186,000 m³), two stations located within the Octeville site but without dumping operations during the study and five stations outside the disposal site (northern and southern zones). The Taxonomic Richness, total abundance and abundances of the polychaete Owenia fusiformis show negative correlations with the volumes of deposited sediment, whereas use of the AMBI (AZTI's Marine Biotic Index) and B2OA (Benthic Opportunist Annelids Amphipods) indices does not allow us to distinguish the impacted zone. Our study shows that the impact of dumping remains local and the benthic habitats display a high degree of resilience with rapid recovery of the community after the cessation of disturbance. Recommendations on the future long-term strategy are proposed to improve assessment and minimise the impact of dumping sediment on this benthic habitat.

Ocean acidification has emerged as a major concern in the last fifteen years and studies on the impacts of seawater acidification on marine organisms have multiplied accordingly. This review aimed at synthesizing the literature on the effects of seawater acidification on tropical scleractinians under laboratory-controlled conditions. We identified 141 articles (published between 1999 and 2021) and separated endpoints into 22 biological categories to identify global trends for mitigation and gaps in knowledge and research priorities for future investigators. The relative number of affected endpoints increased with pH intensity (particularly for endpoints associated to calcification and reproduction). When exposed to pH 7.6–7.8 (compared to higher pH), 49% of endpoints were affected. The diversity in experimental designs prevented deciphering the modulating role of coral life stages, genera or duration of exposure. Finally, important bias in research efforts included most experiments on adult corals (68.5%), in 27 out of 150 (18%) coral ecoregions and exclusively from shallow-waters.

We studied the concentrations of terrestrial and anthropogenic radionuclides in seawater and shore sediment/sand of three selected regions; Khafji, Safaniyah and Menifah along the Saudi Arabian Gulf coast. The mean activity concentrations of the ²²⁸Ra, ²²⁶Ra, and ⁴⁰K in the analyzed sand samples are 5.9, 3.5 and 113.5 Bq/kg, and the respective values in seawater samples are 1.6, 0.8 and 10.4 Bq/L. All data show lower than the corresponding UNSCEAR (2000) reported world average values of 35, 30 and 400 Bq/kg for soil matrix. A few relevant radiological hazards were quantified by the estimation of the absorbed dose rate, and the results are compared with the prescribed limits set by international regulatory bodies. Measured data indicates that the studied coastal regions pose a negligible radiological hazards to the public, and show an insignificant radioactive loading to this coastal region by the Busher nuclear power plant.

Spatiotemporal concentration patterns for 19 parents and their alkyl homologues were measured in Pinctada radiata from 7 locations in the central Arabian Gulf around Qatar in the winter, spring and summer (2014–2015). The concentrations of PAHs ranged from 20 to 2240 (262 ± 38.0 ng·g⁻¹ dw) with the highest occurrence in the Doha harbor (738.4 ± 197.3 ng·g⁻¹ dw) and the lowest in the west coast of Qatar (48.3 ± 5.8 ng·g⁻¹ dw). Residual PAHs in the oysters were about two times higher in winter than in spring and summer (P < 0.05). PAHs in oysters are dominated by 2 and 3 rings PAHs and their alkyls. Alkylated PAHs (APAHs) comprised >55 % of the ΣPAHs. Statistically significant differences in PAHs profiles among oysters were due in part to differences in lipid contents and shell biometrics. Principal component analysis (PCA) and diagnostic ratios for sources identifications suggested that PAHs accumulations in oysters were due to petrogenic and fuel combustion.

The number of studies on microplastic accumulation in marine organisms has increased precipitously recently, though information is geographically-skewed and limited in terms of local effects. We characterized microplastic accumulation in oysters (Saccostrea cucullata) along a Bornean coastline, focusing on spatial variation. Comparisons were made between locally-polluted (Brunei Estuarine System, BES) and relatively pristine, open-shore (South China Sea, SCS) coastlines. Sixteen coloured microplastic types were characterized into three shapes (fragments, fibres, pellets). Fragments (74.9%), especially smaller polypropylene black fragments predominated in the samples (<50 μm, 31.7%). Site-specific levels of microplastic accumulation varied from 0.43 to 7.20 particles/g oyster tissue. BES and SCS sites differed qualitatively, indicating limited interaction. In the BES, accumulation was greatest near the predicted source (Bandar) and declined strongly seawards, implying current flow, environmental sequestration (local sinks) and seawater dilution effects. Such local-scale variation in microplastic loading in estuaries cautions against extrapolating from limited sampling.

Plastic waste is a ubiquitous form of marine pollution and recent studies have identified threats of plastic debris and the associated chemical compounds to wildlife. Sponges pump substantial quantities of water and are important in benthic-pelagic coupling, making them susceptible to interacting with such pollutants in the water column. Here, a method to detect common plastic-associated compounds including phthalates, a phthalate metabolite, bisphenol-A, and a brominated flame retardant in sponge tissue was developed. The method was applied to samples of Xestospongia muta and Niphates digitalis from a reef in the Florida Keys. All sponge samples had quantifiable levels of di(2-ethylhexyl) phthalate, with trace levels of the associated metabolite detected in some N. digitalis samples. There was no quantifiable detection of bisphenol-A, or the brominated flame retardant. This work is a preliminary assessment of the relationship between plastic marine debris and marine sponges.

In this study, the pollution level of heavy metals (HMs), their sources as well as factors influencing their distribution, were studied using data about the concentration of Cr, Pb, Cu, As, Hg and Zn in surface sediment samples from Haiyang coastal areas, and those on sediment grain size and tidal residual currents. Cr, Cu and Pb originated from natural processes and had similar distributions which were mainly affected by sediment grain size, tidal residual currents and coastal currents. Areas with high levels of these elements were also mainly located in the sedimentation zone of fine materials with weak hydrodynamic force. In contrast, Zn and Hg were derived from anthropogenic activities such as industrial sewage and raft cultures, while As originated from both natural and human sources. Overall, sediment grain size, hydrodynamic effects and human activities were the main factors affecting the distribution of HMs in the Haiyang coastal sea.