BENTHIC MICROALGAE UNDER THE INFLUENCE OF beach NOURISHMENT IN THE GULF OF ODESSA (THE BLACK SEA)

The coast of the Gulf of Odessa (Odessa Bay) in the north-western part of the Black Sea is exposed to abrasive processes, which lead to its destruction. One of the measures for landslides stabilization is sand nourishment, which was held on the beach of the gulf in October 2007. As a result of shore protection works, the sand grain size on the beaches of Odessa has decreased by 53% on average. The influence of sand grain size on the abundance and biomass of benthic microalgae was investigated. Benthic microalgae were presented mostly by Bacillariophyta and Dinophyta. Other groups of Chlorophyta, Cyanophyta and Cryptophyta were less presented. The abundance and biomass of algae increased threefold and fourfold, accordingly, as a result of sand nourishment. Significant influence of fine sand particles on the biomass and abundance of microalgae was revealed. However, the structure of algological assemblages changed because of the increase of mixotrophic groups of algae contribution.