Dynamics of periphytic Bacillariophyta at different stages of operation of the Chornobyl Nuclear Power Plant cooling pond (Ukraine)

Abstract

The paper deals with the long-term dynamics of taxonomic composition of diatom periphyton in the Chornobyl nuclear power plant cooling pond (ChNPP cooling pond) at different stages of its operation: before the accident, after the accident and during the present period. The dominant complex of diatoms was marked by the highest diversity in the period after the accident, due to water temperature decreasing and new habitats appearing. The large-scale water-level drawdown in the present period caused the water table to reduce, and the habitats became less diverse. Owing to this, the number of dominant species decreased. Studying the present-day taxonomic composition of periphytic algae in the ChNPP cooling pond by way of light microscopy and scanning electron microscopy made it possible to identify 141 diatom species, represented by 143 infraspecific taxa, from 45 genera, 20 families, 12 orders and 3 classes. 14 species and infraspecific taxa of diatoms from genera Amphora, Cocconeis, Gomphonema, Hippodonta, Karayevia, Navicula, Placoneis, Planothidium, Psammothidium, Sellaphora are new for Ukrainian flora. High contamination of the ChNPP cooling pond with man-made radionuclides 90Sr, 137Cs and the large-scale water-level drawdown did not cause a significant degradation of diatom periphyton, which, in new ecological conditions, is distinguished by high taxonomic diversity and spatial heterogeneity.