The epilithic algal assemblages of Lake Kinneret, Israel

We studied for the first time the effects of geological substrates on taxonomic composition of epilithic algal assemblages in Lake Kinneret and their seasonal fluctuations. It is shown that both species richness and cell densities increase during the winter. Among the fifty-four species identified, the major groups were Bacillariophyta, Chlorophyta, and Cyanobacteria (41%, 37%, and 16%, respectively). The dominant alga on stony substrates throughout the study period was the diatom Gomphonema sp., accompanied by Cymbella sp., Navicula spp., and Nitzschia spp. The Chlorophyta were represented by Cladophora glomerata (Linnaeus) Kutzing, Tetraedron minimum (A.Braun) Hansgirg, and the Cyanobacteria by Lyngbya sp. The substrate effect on algal growth was also determined. The results show that 66%, 20%, and 14% of all epilithic algae were found on limestone, basalt, and flint, respectively. In the depth profile, two peaks of epilithic algae were revealed. The first was found at 0.25-0.70 m, dominated by the Bacillariophyta Gomphonema sp., Nitzschia spp., Navicula spp., Cymbella sp., Cocconeis sp., Achnanthes sp., and Synedra ulna (Nitzsch) Ehrenberg. A second peak was found between 1.20-1.60 m, with Chlorophyta, mainly Cladophora glomerata, being dominant. The Cyanobacteria Lyngbya sp. and Chroococcus sp. were evenly distributed at all depths.