Ostracod assemblages from the Golubaya (Rybatskaya) Bay area on the outer northeastern Black Sea shelf over the last 300 years

Abstract

A multi-proxy study of core Ash-2012-02 from the outer shelf of the northeastern Black Sea allowed us to define recent environmental changes, on a seven-year period resolution for the last 300 years. The age model of the core Ash-2012-02 based on radionuclide (210 Pb, 137 Cs, 241 Am) measurements suggests an average sedimentation rate of 1.4 mm/y and, consequently, a sedimentary record from end of the Little Ice Age to present. We subdivided the core section into five intervals mainly based on changes in relationships between ostracod species and their total abundance. Besides, the modern ostracod distribution on the northeastern Black Sea shelf was studied. Six main habitats with a specific ostracod species composition and environmental conditions have been investigated, as well as information on the temperature and salinity preferences for some ostracod species was provided. The ostracod species composition of assemblages remained similar throughout the core, but there were significant variations in the main ostracod species and the foraminiferal abundance. The hydrodynamic variations caused by climatic changes in the region are responsible for oxygen content in the bottom waters and affect the structure of the faunal assemblages. During the second half of the 20th century, an increasing trend of TOC and CaCO3 as well as considerable reduction in the ostracod diversity and the ostracod and foraminifera abundance are recorded in the muddy habitats, likely associated with unfavorable oxygen conditions and increased anthropogenic pressure.