Desmids of the Staurastrum tetracerum-group from a eutrophic lake in mid-wales

Abstract

Seven desmids have been found in the phytoplankton of a markedly eutrophic lake in mid Wales. All have grown well in laboratory cultures and so an opportunity has been provided to explore the taxonomy and morphological variability of four species, Staurastrum tetracerum, S. irregulare, S. bibrachiatum and S. pseudotetracerum, previously described inadequately. Suggestions for nomenclatural changes are made for S. irregulare and the very variable S. bibrachiatum, which is recorded from the British Isles for the first time. Reasons for the occurrence of the seven desmid species in the eutrophic lake plankton are discussed.