State of zoobenthos and marine ecological status along the central part of the Gulf of Finland in 2020, Baltic Sea

Abstract

The aim: to assess the ecological state of the Gulf of Finland in the summer of 2020 using the benthic index of the ratio of opportunistic polychaetes/amphipods (BOPA) and the benthic index of the ratio of opportunistic annelids/amphipods (BO2A). Research material and methods : the material was collected during the 55th cruise of the PV Akademik Ioffein July 2020. To assess the ecological state of the Gulf of Finland CTD‑soundings and macrozoobenthos data were used, the BOPA and BO2A indices were calculated. Results: the obtained values of the ecological state of water body based on the BOPA and BO2A indices in this study characterize the quality of the sea along the central part in the Gulf of Finland. The negative statistically significant correlation between indices BOPA, BO2A and concentration of the dissolved oxygen are established. Practical significance: a complete picture of the ecological state of the Gulf of Finland in 2020 was obtained. The presented data showed that the concentration of dissolved oxygen in the bottom layer, under conditions of unstable salinity stratification, affects the values of the BOPA and BO2A indices through the tolerance of various taxonomic groups. BOPA and BO2A indices can be used in assessing water quality