A comparative analysis of the community structure and seasonal dynamics of quantitative parameters of cyanobacteria in periphyton and epilithon in Karantinnaya Bay in the Black Sea, linking them to the environmental factors.

The total number and biomass of cyanobacteria were quantified on the basis of established methods for the benthic cyanobacteria.

The abundance and biomass of cyanobacteria were 0.38 × 10⁶–4.20 × 10⁶ cells cm⁻² in periphyton and 0.004 × 10⁶–0.158 × 10⁶ cells cm⁻² in epilithon, 0.0035–0.160 mg cm⁻² in periphyton and 0.00002–0.004 mg cm⁻² in epilithon. Maximum values were recorded in November for periphyton and August for epilithon; minimum values were recorded in March. Thin filamentous cyanobacteria are more responsible for changes in abundance, and biomass is determined by thick filamentous species, and in their absence, by unicellular cyanobacteria.

Cyanobacterial communities in periphyton and epilithon differed in density, seasonal dynamics, dominant species composition and response to the nutrient contents. Nitrogen, phosphorus and their ratio at optimal pH were most important for cyanobacteria, but the requirements for certain nutrients varied between biotopes.

This study will clarify microbial assemblages’ ecological roles in coastal ecosystems and their utility as sensitive biomonitoring indicators.