Metazoan Microzooplankton in the Crimean Coastal Waters of the Black and Azov Seas in Spring: Composition, Abundance and Spatial Distribution
The study was carried out during the 84<sup>th </sup>expedition of RV “Professor Vodyanitsky” in the coastal waters of the Black and Azov Seas from 19 to 26 April 2016. The goal of the study was to assess the abundance and species composition of the “spring” micrometazooplankton (MMZP), providing previously unavailable data. A total of 59 samples were collected at 20 stations within the upper 50-m layer of water. The average MMZP abundance in the surface layer of the Black Sea waters was 14.8 ± 5.8 thousand ind. m<sup>-3</sup>. The greatest number (up to 35 thousand ind. m<sup>-3</sup>) was observed in the coastal waters of Kalamitsky and Karkinitsky bays and the smallest (1-13 thousand ind. m<sup>-3</sup>) in the waters of the south coast of Crimea. In the Azov Sea, MMZP abundance was almost one order of magnitude higher and ranged from 52.4 to 198.6 thousand ind. m<sup>-3 </sup>in the surface layer and from 39.0 to 89.0 thousand ind. m<sup>-3 </sup>in the bottom layer. The species composition of the MMZP in the Black Sea waters was characterized by the predominance of the crustacean fraction with copepods as its major part (81.9 and 77.4% of the total abundance, respectively). In the Azov Sea, meroplanktonic larvae of barnacles dominated, constituting over 65%; larvae of polychaetes, bivalve veligers, and rotifers were also abundant. The vertical distribution patterns were determined by the biotope and predominant composition of MMZP. The abundance maxima in the middle and lower layers of the water column in the shallow-water zones were associated with veligers of mollusks while copepods were responsible for the local maxima in different layers of deeper habitats, where they dominated.