Emiliania huxleyi fluctuation and associated microalgae in superficial sediments of the Romanian Black Sea shelf

Abstract

Several sites from the NW Black Sea, namely, the Romanian Black Sea shelf, situated at water depths ranging from 17 m to 80 m, have been investigated. The superficial sediments, i.e., the water/sediment interface, were analyzed for their calcareous nannoplankton content. Both quantitative and qualitative nannofloral analyses have been performed. The nannofloral assemblages that are in situ contain only Emiliania huxleyi and Braarudosphaera bigelowii. Offshore, in front of the Danube mouth, only resedimented calcareous nannofossils from older Mesozoic-Tertiary deposits are present. Concerning the nannofloras in situ, the maximum bloom of Emiliania huxleyi in the studied area is placed in the region where the influx in sediments and waters rich in nutrients is significant, due to the input of both the Danube and Dniepr rivers, at a distance exceeding 30-40 km from the coastline. Apart from the coccolithophore algae, other groups of organisms, such as silicoflagellates, diatoms and dinoflagellates, were recorded. Their distribution pattern clearly
reflects the marine setting; hence, differences in abundance and diversity between the inner and outer shelves have been observed.