CYANOPROKARYOTE AND ALGAL BIODIVERSITY IN THE TROPICAL LAKE EDWARD (AFRICA) WITH NOTES ON NEW, RARE AND POTENTIALLY HARMFUL SPECIES

The paper presents data on the biodiversity of prokaryotic and eukaryotic algae in the tropical Lake Edward, compiled from publications of the Damas mission (1935-1936), Hecky & Kling (1987) and our own results from a recent investigation of the lake phytoplankton in a three-year period (2016-2018) in the frame of the HIPE (Human impacts on ecosystem health and resources of Lake Edward) project (http://www.co2.ulg.ac.be/hipe). The provided checklist is based on modern algal taxonomy with relevant synonymizing of lists of previous authors.
In total, 577 taxa from seven divisions were registered in the lake waters and in the Kazinga
Channel. The richest division was Ochrophyta (287 taxa, 274 of which from Bacillariophyceae),
followed by Chlorophyta (131 taxa), Cyanoprokaryota (134), Streptophyta (14), Euglenophyta
(8), Pyrrhophyta (5) and Cryptophyta (1). 52 species (or only 1% of the taxa found) persisted in the lake since 30s of the 20th century till nowadays. More than half of the cyanoprokaryotes (65) are potentially toxic and harmful species. The checklist contains also data on algal abundance and frequency of occurrence, originally provided by the authors. In the phytoplankton samples, collected during the three cruises of the HIPE project, 248 taxa were found, among which the richest division was Cyanoprokaryota (104). From this total of 248 taxa, only 3 were frequent and 199 were very rare (from 1-3 samples) with 121 taxa found in one sample only. During 2016-2018, the most abundant species in the lake phytoplankton belonged to Cyanoprokaryota, Bacillariophyceae and Chlorophyta. The algae found in the lake have different ecological requirements and besides clear tropical species and some cosmopolites, some “cold water species” from northern and temperate regions were found. For them, as well as for some thermophilic species, considered alien for the lake, transport through different vectors was supposed. In the literature analyzed, 36 new taxa were described. Among them 26 taxa had Lake Edward as a single locality, and 10 were found also in other lakes and adjacent water bodies. Twelve of these new taxa were checked by modern taxonomists, but 24 still need taxonomic reconsideration.