Benthic diatom species richness at Dvuyakornaya Bay and other coastal sites of Crimea (Black Sea) under various environmental conditions

Abstract

Initial research of the pristine waters of Dvuyakornaya Bay (South-eastern Crimea, Black Sea) revealed a high taxonomic richness in benthic diatoms (Bacillariophyta). A total of 304 species, 78 genera, 37 families, and 20 orders were identified. Among these, 68 novel species for the Black Sea were noted. The largest number of species was identified in the genera Navicula (41 species), followed by Nitzschia (29), Amphora (25), Cocconeis (20), Diploneis (16), Lyrella, Fallacia, and Planothidium (10 species each, respectively). An inter-regional comparative analysis of diatom species richness was performed using Bray-Curtis similarity coefficient and Venn diagrams. The diatom taxocene of Dvuyakornaya Bay (DB) was compared with Bacillariophyta flora from several Crimean coastal sites under different levels of anthropogenic impact, i.e. relatively pristine waters near Cape Fiolent (CF) and heavy polluted Sevastopol Bay (SB) and Balaklava Bay (BB). The highest species composition similarity (58%) was registered between intact biotopes (DB vs CF) and between heavily polluted areas (SB vs BB), despite the geographical remoteness of the compared areas as well as differences in their hydrological-hydrochemical conditions and bottom substrates patterns. The lowest diatom taxocene species similarity was observed between SB and CF (32.3%) and between SB and DB (36.5%). It was concluded that the content of technogenic pollutants (trace metals, PCBs, PAHs, and pesticides) in the bottom sediments, as well as the heterogeneity of microbiotopes, represent major factors influencing the species composition of benthic Bacillariophyta in the investigated coastal areas.