Dinoflagellate cyst assemblages as indicators of environmental conditions and shipping activities in coastal areas of the Black and Caspian Seas

Abstract

Pontocaspian ecosystems have deteriorated due to increasing anthropogenic pressures, including shipping activities. We studied the relationships between sedimentology, environmental and shipping variables, and the dinocyst distribution and abundance across the Pontocaspian region. Cyst diversity was characterized by the presence of 36 dinocyst morphotypes. Western Black Sea assemblages were dominated by Lingulodinium machaerophorum and Round brown cysts reaching values of 60% and 31.6% respectively. Lingulodinium machaerophorum, Impagidinium caspienense and Round brown cysts dominate the Caspian Sea assemblages with relative abundances of 80, 68 and 52%, respectively. Temperature, salinity and primary productivity are the main drivers for dinocyst distribution and species assemblages. Temperature controls the distribution and relative abundance of the potentially toxic species L. machaerophorum. Dinocysts assemblages reflect enriched-nutrient conditions in the North Caspian Sea and the Western Black Sea. Distance from the harbour correlates with dinocyst assemblages in the North and Middle Caspian Sea. This is likely to be related to the high shipping activities.