Diversity and ecology of small coccoid green algae from Lake Itasca, Minnesota, USA, includingMeyerella planktonica, gen. et sp. nov

We characterized 81 isolates of picoplankton and other small planktonic coccoid green algae from Lake Itasca, Itasca State Park, MN, USA. Sequence analysis and examination by light microscopy revealed three common algae: Pseudodictyosphaerium/Korshpalmella spp. (Chlorophyceae), Choricystis spp. (Trebouxiophyceae) and a previously undescribed autosporic coccoid. The Pseudodictyosphaerium and Korshpalmella species that were evaluated all possessed identical 18S ribosomal DNA (rDNA) and rbcL sequences, but this 18S rDNA sequence differed from the published 18S rDNA sequence for P. jurisii isolated from Europe. These chlorophycean algae were isolated from samples collected from Lake Itasca during all seasons. The 18S rDNA sequence of some of the Itasca isolates of Choricystis was nearly identical to the published sequence for C. minor; however, six different rbcL sequences were detected among the Choricystis isolates and none of these rbcL sequences matched published sequences for isolates from sever...