A numerical model was applied to simulate the transport of ¹³⁷Cs released with the waters which were used to cool Fukushima reactors. These stored waters will be released to the Pacific Ocean according to Japanese government plans. The radionuclide transport model is Lagrangian and includes radionuclide interactions with sediments and an integrated dynamic foodweb model for biota uptake. Calculations made from a conservative approach indicate that expected concentrations in sediments and marine fish would be orders of magnitude below those detected after Fukushima accident and also lower than those resulting from global fallout background.

Seafloor litter was investigated in the Bohai Sea, Yellow Sea, and northern East China Sea (BYnECS) based on fisheries-independent bottom trawl surveys in 2019. The mean density of seafloor litter was 48.44 items∙km⁻² (44.56 kg∙km⁻²) in the BYnECS, which was at an intermediate level compared with the values observed in other continental shelf areas worldwide. There were significant differences in the density of seafloor litter among different regions (P < 0.05), and the high-density litter accumulation areas in the northern Yellow Sea and Changjiang estuary and adjacent waters were close to the sediment accumulation areas. Plastics were predominant in the BYnECS and accounted for 72.80%/44.05% (number/weight) of the seafloor litter. Fishery-related litter was the main source of seafloor litter in the BYnECS. This study systematically reports the density, composition, sources and spatial distribution of seafloor litter in the BYnECS, thereby providing a scientific basis for the management of marine litter.

Contaminants adsorbed on microplastics (MPs) are a potential risk to aquatic environments. Several studies have demonstrated that polycyclic aromatic hydrocarbons (PAHs), which adsorb on MPs, can be photolyzed in aqueous solutions. We investigated photolysis of PAHs on MPs under sunlight conditions to estimate their environmental fate for the first time. The PAHs (25 ng each) were added to polyethylene powder, which was used as the MP sample. The MP sample was agitated in water with sunlight irradiation; thereafter, the concentration of the PAHs on the MP sample was determined by high-pressure liquid chromatography with a fluorescence detector. The half-life values of the PAHs were estimated between 3.4 × 10² (pyrene) and 3.2 × 10⁴ min (benz[j]fluoranthene). These values are 0.5 (fluoranthene) to 25 (benzo[a]pyrene) times larger than those in the aqueous phase. Additionally, the degradation of PAHs by OH radicals produced by the photolysis of nitrate was observed.

Bivalves are the focus of experimental research as they can filtrate a broad size range of microplastics (MPs) with negative consequences for their physiology. Studies use a range of MP shapes, materials, sizes and concentrations raising the question on whether these reflect environmental observations. We review experimental studies on the effects of MPs on marine bivalves and contrast the MP characteristics used with corresponding data from the environment. Mussels were the most common bivalve across experiments which reflect their high abundance and broad distribution in the field. Although fibres are the dominant shape of MPs in coastal systems, most studies focus on spherules and beads, and MP concentrations are often orders of magnitude higher than environmental levels. For higher relevance of experimental findings we recommend that maximum experimental concentrations of MPs are in the range of 100–1000 particles/L, that there is more focus on microfibers and that concentration is reported in particles/volume.

The death of microalgae plays an important role in ocean energy flow and material circulation. The existing methods for the identification of dead and living microalgae cells all have defects such as the need for staining and pre-treatment. In this work, a label-free method to identify living and dead algae cells based on digital holography microscopy and machine learning was designed. At the stage of model training, ten feature vectors were extracted from the holograms, and twelve classification models of machine learning algorithm were trained. Compared with the staining method results, the accuracy of this method can reach 94.8%. At the stage of field verification, the death rate calculated by this method was also consistent with staining method. The method proposed in this paper provides a new method for the study of marine microalgae death which has the advantages of label-free, non-invasive, high accuracy and potential for in-situ application.

The hydromedusa Blackfordia virginica is an invasive species that has disrupted coastal marine food webs throughout the world. Here, we report the response of plankton community to B. virginica blooms in a subtropical lagoon in China. Chlorophyll-a concentrations increased after the peak of B. virginica abundance, which was coincident with high concentrations of ammonium. An increase of the biomass and composition of pico- and nano-phytoplankton during the bloom resulted from bottom-up effects due to the nutrients excreted by B. virginica. The average size and grazing rates of microzooplankton concurrently decreased. The negative correlation between the abundances of B. virginica and microzooplankton was accurately simulated by a generalized linear model and redundancy analysis. This study provided empirical evidence of the impacts of the B. virginica bloom on the food web and the mechanisms responsible for those effects. These impacts may lead to serious ecological and environmental consequences for the lagoonal ecosystem.

Eighteen trace elements were analyzed in a 120-year sediment core from Daya Bay. Burial flux history and potential provenance, the relationships among trace elements, and biogenic compositions were analyzed for determining the trend and extent of trace element accumulation and identifying corresponding anthropogenic effects. Additionally, the effects of anthropogenic activities on Daya Bay were reconstructed, and a baseline/background estimation was provided for Daya Bay. The burial fluxes of V, Cr, Cd, Cu, Zn, Mn, Fe, Co, Ni, Pb, Hg, Zn, Mo, Ag, As, Se, and Tl increased from 1960 to 2010, especially after the late 1980s. Our results are useful for understanding pollution and land-sea interactions along the coasts of the South China Sea, especially in the Guangdong-Hong Kong-Macao Greater Bay Area.

Statistically distinct ‘high’, ‘moderate’ and ‘low’ metal contamination positions were distinguished across five Sydney estuary embayments for total sedimentary metal concentrations of Ni, Pb and Zn. While statistically distinct total sedimentary As, Cd, Co and Cu concentrations were indicated for the ‘low’ position samples. Mangrove (Avicennia marina) pneumatophore tissue metal concentrations from ‘high’ position trees were statistically distinct for Cd, Ni, Pb and Zn, while root tissue samples from ‘low’ position trees were statistically distinct for As, Cd and Zn. Outcomes from CAP, simple linear regression and DISTLM modelling indicated sedimentary metals were predominantly assimilated into mangrove root tissue, with smaller uptake into pneumatophore tissue. A comparison of floristic tissue metal concentrations indicated mangrove (A. marina) root tissue assimilated higher sedimentary metal concentrations than leaf and root tissue of seagrasses (Zostera capricorni and Halophila ovalis), which had relatively higher metal concentrations than those from pneumatophore and leaf mangrove tissue.

Gillnets can cause impacts on marine ecosystems when they become abandoned, lost or otherwise discarded fishing gear (ALDFG). Fishing gear marking is a tool to address ALDFG and its impacts. This study aims to compare the characteristics and fishing activities of fishers in small-scale fishery (SSF) and industrial fishery (IDF) as well as their viewpoints on fishing gear marking practice. Data were collected during July-November 2020 from 95 fishers in five coastal provinces of Thailand. Most fishers used crab gillnets; besides, fishing capability and intensity of fishers in IDF were higher than in SSF. Awareness of fishing gear marking practice of fishers in IDF was higher than in SSF, but acceptance was not different. Preferred material was fabric for fishers in SSF and plastic for fishers in IDF. Most fishers anticipated government as producer. Moreover, further studies are needed to develop suitable materials, installation and cost for fishing gear marking.

The commercially important marine microalgae Nannochloropsis oceanica is easily ingested by protozoan predators during large-scale cultivation. However, investigations into the effect of microalgae on the growth of protozoa are scant. A feeding experiment was conducted with Euplotes vannus grazing on different concentrations of N. oceanica. The ciliate population was significantly lower in the high concentration of algae than that in the low or medium algal concentration treatments. The density of ciliates cultured in algae filtrate media was significantly lower than that in lysate media and the blank control. Furthermore, the algal cell filtrate was added to three other protozoan populations, and they all gradually lost their ability to move and their body shape changed. This study investigated the interactions between N. oceanica and protozoan predators and provides insight on using microalgal extracellular substances to control biological contamination in the future.