Persistent organic pollutants and the Mussel Watch Program in the Sea of Japan (Peter the Great Bay)

Persistent organic pollutants (POPs) are among the most hazardous and under-investigated compounds. They are characterized by bioaccumulation, biomagnification, high toxicity, and the ability to migrate through water and air masses far from the original pollution source. Despite the signing of the Stockholm Convention in 2001, some countries still retain the right to use DDT for sanitary and epidemiological control purposes. This study aims to estimate current levels of POPs in the soft tissues of Mytilidae bivalve mollusks (Crenomytilus grayanus, Modiolus kurilensis, Mytilus trossulus, and Mytilus galloprovincialis) and to analyze temporal trends in toxicant accumulation by comparing the current data with results from earlier studies, using the Sea of Japan and the Asia-Pacific region as case examples. Samples of mollusk soft tissues were collected from various locations in Peter the Great Bay during the summers of 2017 and 2018 (See Fig. 1). Additional specimens from Amur Bay were collected during the summer-autumn period of 2022 (See Fig. 1 ). Concentrations of persistent organic pollutants (POPs), including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), were measured in the samples using gas chromatography with an electron capture detector (GC-ECD). The results revealed the presence of persistent organic pollutants (POPs) in all samples analyzed, ranging from 0.6 to 12,955.1 ng/g lipid weight (lw). The highest concentrations of organochlorine pesticides (OCPs) were detected in mollusks from Amur Bay (See Fig. 2). Isomers of hexachlorocyclohexane (HCH) were predominant, with P-HCH as the main form (447.02 ± 1612.00 ng/g Iw), indicating long-term pollution. Among DDT and its metabolites, degradation products (DDE and DDD) were dominant. The major metabolite, o,p"-DDE, was found at concentrations ranging from 4.2 to 453.37 ng/g lw. However, almost all specimens also contained the original compounds (o,p’-DDT and p,p’-DDT), suggesting recent exposure to the toxicant. The lowest levels of OCPs were detected in samples from Cape Kozmina (20.12 ± 4.78 ng/g lw), which may be related to specific flow dyke issues in Nakhodka Bay (See Fig. 2). The highest concentrations of PCBs were found in Amur Bay (See Fig. 3). The primary congeners were highly chlorinated PCBs: 118 (70.53 ± 79.83 ng/g lw), 153 (62.94 ± 63.14 ng/g lw), and 138 (65.63 ± 97.37 ng/g lw), indicating a historical input of these toxicants. The lowest levels of PCBs were detected near Bolshoy Pelis Island, likely due to the absence of local pollution sources (See Fig. 3). Time trend analyses showed a gradual decrease in DDT and PCB concentrations; however, a slight increase in HCH isomer levels was observed (See Table 2). When comparing these data with published results from the Asia-Pacific region (APR), it was found that DDT and PCB concentrations in Russia were lower than those in most APR countries (See Table 3). However, the detected HCH concentrations exceeded those reported in nearly all countries in the region and were comparable to the levels observed in China (See Table 3). The article contains 3 Figures, 3 Tables, 14 References. the authors thank Olga V. Podgurskaya (Cand. Sci. (Biol.), NSCMB FEB RAS) for providing samples of biological material. The Authors declare no conflict of interest.

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