First data on the summer phytoplankton composition of 21 microreservoirs in Bulgaria and their floristic similarity

Abstract

The present paper provides first detailed data on the phytoplankton species composition collected during two summer campaigns (2019 and 2021) from 21 Bulgarian microreservoirs (<100 ha). By conventional light microscopy (LM) 414 algae from seven phyla were identified, among which Chlorophyta were the taxonomically richest group (143 taxa). The recorded high algal biodiversity corresponded to the average species contribution of 36 taxa per site. It was associated with a significant variability between the phytoplankton composition in different microreservoirs: the total number of species ranged from 9 to 97. The dominant/co-dominant and sub-dominant phytoplankton composition comprised 46 algae from six phyla, most of which were cyanoprokaryotes (26 species, out of which 17 dominated in 12 microreservoirs and 11 sub-dominated in seven microreservoirs). The floristic similarity estimated through Sørensen’s Correlation Index (SCI) was quite low (0-43%) corresponding to the high number of species (256, or 61%) found in a single waterbody. We strongly believe that the obtained results will stimulate further investigations of such small waterbodies as unexplored genetic reservoirs of algae.