Periphytic diatoms in the presence of a cyanobacterial bloom: A case study of the Vrutci Reservoir in Serbia

Abstract

Despite their unique ecology and implications for ecological assessment, diatoms in lentic ecosystems are still insufficiently studied in both scientific research and operational monitoring. In particular, the ecology of periphytic diatoms relative to the global expansion of cyanobacterial blooms in lakes has not been described at all. This study aims to describe the diversity and dynamics of a periphytic diatom community in the Vrutci Reservoir during Planktothrix rubescens bloom, and to evaluate the adequacy of standard diatom index implementation in lentic ecosystems relative to the diatom index adapted for lakes - the Trophic Diatom Index for Lakes (TDIL). The study was conducted in the Vrutci Reservoir in western Serbia. Periphyton was developed on an artificial glass substrate during the summer of 2015, following a depth gradient of a stratified water column. Diatom diversity and abundance, as well as diatom indices were estimated. Discounting the cyanobacterial bloom, 79 taxa of diatoms were recorded and among them the species Aneumastus stroesei as the first representative of the entire genus Aneumastus ever to be detected in Serbia. Diatom distribution along the depth gradient was clearly associated with shifts in environmental conditions. TDIL showed an advantage over standard diatom indices in terms of stability during experimental period and uniformity along the depth gradient, indicating the necessity for further testing of this index performance in lakes, and consequently local water-quality legislation update.