FIRST ASSESSMENT OF THE PRESENCE OF MICROPLASTICS IN BIVALVE MOLLUSKS OF WATER BODIES OF THE TRANSITIONAL “RIVER–SEA” COMPLEX IN THE WESTERN PART OF THE VOLGA DELTA

Abstract

The article presents the results of the first study of microplastic content in bivalve mollusks (Bivalvia) in the transitional “river-sea” zone of the western part of the Volga delta. Sampling was carried out in 2024–2025 at sites with different hydrological regimes: natural (“slow flow”) and anthropogenically modified (“fast flow”). The detected microplastic particles were represented by fibers; their identification was performed visually under a stereomicroscope using the “hot needle” method, without spectroscopic determination of polymer composition. The obtained values should be considered as preliminary estimates of the content of presumably microplastic. The content of presumably microplastic particles in bivalve mollusks at individual stations varied within 0.08–1.60 particles/ind. during the autumn low-water period and 0.26–0.29 particles/ind. during the flood period. It is important to note that presumably microplastic in mollusks at the “fast flow” site of the marginal filter of the Volga delta during the autumn period was one and a half times lower than at the “slow flow” site. This is explained by differences in the hydrological regime of the studied areas, where the “slow flow” site acts as the most effective zone for retaining suspended matter, including presumably microplastic particles. The obtained results represent important baseline data for monitoring anthropogenic pollution and developing strategies to mitigate its consequences in vulnerable ecosystems of the Volga delta and the Northern Caspian.