Biomarkers of stress in common coastal amphipods and bivalves under salinity gradient and pollution influence (the White Sea)

Studies of the biochemical parameters of aquatic organisms are important for understanding the mechanisms of their adaptive reactions in response to the influence of environmental factors. They are also used in a comprehensive assessment of the quality of the aquatic environment under the influence of anthropogenic pollution. The purpose of the work is a comparative study of the biochemical parameters of marine invertebrates, showing neurotoxic effects, the process of antioxidant protection, and the functioning of the biotransformation system. These indicators are considered “biomarkers of stress” in aquatic organisms. Widespread White Sea species were chosen as model species: Gammarus oceanicus (Amphipoda: Malacostraca), Mytilus edulis (Mytilida: Bivalvia), and Mya arenaria (Myoida: Bivalvia). At the end of August 2015–2016, these invertebrates were collected from several locations of the littoral zone of the Kandalaksha Bay of the White Sea: the wild littoral in the absence of visible anthropogenic influence, and with different levels of local pollution (far from an urban settlement (Maly Pitkul Bay), on a wild beach near the confluence of the Niva River, near the port of Kandalaksha at the boat pier, and at the Kartesh biological station). In addition, a comparison was made between molluscs (M. edulis) living in the intertidal and subtidal zones (as part of mussel rope aquaculture). The highest levels of enzyme activity (catalase, glutathione-S-transferase) and increased levels of lipid peroxidation, indicating the state of oxidative stress in the amphipods and molluscs, were determined for animals living at the mouth of the Niva River and local pollution with oil products in the port of Kandalaksha. For each indicator, interspecies differences in response to impacts of one nature or another were found. Principal component analysis revealed two factors that explained 81.08% of the variability of the variables. The main influencing factors were the river reducing the salinity of the water and introducing pollutants into the sea, increasing the levels of metals (copper, zinc, and lead) in the water. The second important impact factor was local pollution of habitats with oil products (motor boats), and it was this second factor that was associated with changes in a large number of biochemical parameters of molluscs and amphipods, indicating the state of stress in organisms. The results of this study confirm the usefulness of using biochemical indicators of marine invertebrates to assess their condition under the influence of environmental stress factors, including pollution, and the high indicator significance of the applied biomarkers.