ENVIRONMENTAL CONDITIONS INFLUENCING THE DISTRIBUTION OF BENTHIC FORAMINIFERA IN THE BALTIC SEA AS A BASIS FOR GEOECOLOGICAL MONITORING

Abstract

The expansion of hypoxic zones and the acceleration of eutrophication, caused by both natural and anthropogenic factors, have a significant negative impact on the Baltic Sea ecosystem. A synthesis of all available domestic and international studies (27 publications, 1930–2020) researching modern benthic foraminifera in the various basins of the Baltic Sea (Arkona, Bornholm, Gdańsk, and Gotland) and the straits (Kattegat and the Danish Straits), together with our own investigations in the southeastern part of the sea, we compiled a database of taxa and environmental factors controlling their distribution. Over the course of research development and data accumulation, the focus has shifted from documenting species diversity to detailed examination of the broad range of ecological conditions of benthic foraminiferal habitats; however, such data remain scarce and fragmented. The compiled data allowed us to delineate groups of taxa associated with limiting environmental factors such as salinity and bottom-water dissolved oxygen, as well as organic carbon content in bottom sediments. For the southeastern Baltic, based on a comparison of cruise data from 1978, 2016, and 2018, salinity below 12 psu was confirmed as the primary factor limiting the distribution of calcareous tests of Elphidium sp. indet. An increase in species diversity was observed over this period, which may be attributable to methodological differences, underscoring the need to standardize micropaleontological protocols in geo-environmental monitoring. The compiled table of ecological preferences of benthic foraminiferal taxa can serve as a basis for monitoring the state of the Baltic Sea ecosystem and for reconstructing past hydrochemical and hydrological changes.