Recent bloom of filamentous algae in Lake Baikal is caused by Spirogyra Link., 1820 of local origin

Abstract

Molecular phylogeny inferred from rbcL nucleotide sequences obtained from the single sterile filaments of green algae collected around the perimeter of Lake Baikal indicates the polyphyletic origin of the representatives of genus Spirogyra Link., 1820 inhabiting the lake. The common ancestor of all Baikal Spirogyra dates back at least to 20 MYA. This roughly coincides with the age of continuously existing freshwater body in the confines of current Baikal. The descendants of this node include both Baikal and non-Baikal species and thus suggesting a complex history of multiple emigrations and immigrations. There is at least one major lineage of the Baikal Spirogyra in the phylogeny descending uninterruptedly from the common ancestor of all Spirogyra species found so far in the lake. The likely explanation is its permanent presence in the ecosystem. All this allows us to hypothesize that the current bloom is a spectacular but natural response of the Baikal ecosystem to the increased pollution.