Microscopic eukaryotes living in a dying lake (Lake Koronia, Greece).

The morphological and phylogenetic diversity of the microscopic eukaryotes of the Lake Koronia water column was investigated during a mass kill of birds and fish in August-September 2004. The dominant morphospecies corresponded to the known toxin-producing species Prymnesium parvum, followed by Amoebidium sp., a taxon belonging to the group of parasitic Mesomycetozoea, and the common chlorophyte Pediastrum boryanum. Prymnesium exhibited heteromorphic life-cycle stages (flagellate and nonmotile coccoid cells). Phylogenetic analysis with 18S rRNA gene suggested that these heteromorphic stages belonged to the Platychrysis-Prymnesium monophyletic group. The most abundant phylotype was almost identical to P. boryanum. The fungal phylotypes were related to the Chytridiomycota, and the ciliate-like ones were closely related to Enchelys polynucleata and Pattersoniella vitiphila. Two phylotypes representing novel members belonging to the Jakobida and the Apicomplexa were also found. The microscopic eukaryotes of Lake Koronia include several organisms that are related to parasitic life modes.