Taxonomic diversity and structure of benthic diatom taxocenes (Bacillariophyta) along the Crimean Coast (the Black Sea)

Diversity and structure of benthic diatom assemblages in 16 Crimean nearshore habitats with varying levels of technogenic bottom area pollution at depths range 0.5–50 m were investigated and accessed using Taxonomic Distinctness indices (TaxDI). In total 793 species and intraspecific taxa, belonging to 736 species, 130 genera, 53 families, 27 orders and 3 classes of Bacillariophyta were registered. The structure of diatom assemblages from polluted sites can be described as having low species richness and a large proportion of mono- and oligospecies branches at the family and order levels. In locations under a moderate anthropogenic impact, the structure was characterised by relatively high species richness and an equal ratio of oligo- and poly-species branches closed at genus level, with the presence of monospecies branches converging at family or order level. Taxocenes in pristine sites were distinguished by the highest species richness and a predominance of poly-species branches closed at different hierarchical levels.