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The estuaries of the Razdolnaya and Partizanskaya Rivers in the Peter the Great Bay were chosen to conduct the comparative studies of the effects of pollution on aquatic organisms. Corbicula japonica, a bivalve mollusk, was used as an indicator species. Molecular biomarkers in the digestive gland and gills of C. japonica were used to determine the indicators of oxidative stress, such as lipid peroxidation (malondialdehyde), antiradical activity, DNA damage and microelement composition of tissues. High concentrations of iron, zinc and lead were identified in the tissues of C. japonica from the Partizanskaya River. A high concentration of copper was found in the tissues of those from the Razdolnaya River. The level of lipid peroxidation products in the digestive gland of C. japonica from the Partizanskaya was higher than that of the other areas under study, Moreover, the level of antiradical activity and the genetic damage index in its tissues were two times higher. It is found that chronic oxidative stress is observed in all the estuaries under study. The proposed biomarkers clearly show the state of C. japonica in the biotopes of different pollution levels, indicating that the worst state is attributable to the estuary of the Razdolnaya River.

The article touches upon the problem of sustainable development of the sea hydrobionts. Deep-sea scallop Mizuhopecten yessoensis is one of the most common breeding species in Primorsky Kray usually grown by two methods: cage and bottom. The cage (industrial) cul-tivation type is the most developed, but requires close attention. Improper planning of the mariculture development can affect the scallop survival, which in turn will lead to significant financial losses. Nowadays mariculture farms in different countries register the mass mortality of the cultivated aquatic organisms, the causes of this phenomenon being not clear, and often their identification requires a lot of time, as well as financial expenses. The use of prognostic mechanisms based on biomarkers can help identify the hidden threats in the body of cultivated scallops that lead to the mass mortality. The assessment of the state of mollusks at earlier stages of development will allow predicting and preventing significant losses of commercially valuable species. There have been analyzed the biomarker and scallop mortality rates of the scallop Mizuhopecten yessoensis cultivated by the cage method. Different groups of mollusks from 2 generations with the age difference of 10 years have been evaluated. In the course of the study it was found that with the increasing number of DNA defects and active accumulation of malondialdehyde in tissues the mortality of mollusks increases. It was stated that in scallops aged 1+ generations of 2015 there were registered the great number of DNA molecule defects and the high level of malondialdehyde concentration in the digestive gland and in the gills, which subsequently led to the mortality of almost all commercially valuable species aged 3+.