Distribution of Dolichospermum in European waterbodies: a multidisciplinary approach

Dolichospermum lemmermannii is distributed in northern temperate and boreal regions. In the last 20 years, this Nostocales species appeared in all the large (62-368 km2) lakes south of the Alps (Garda, Iseo, Como and Maggiore), often in the form of summer water blooms. The study of the sub-fossil akinetes in sediment cores allowed to antedate the introduction of Dolichospermum in Lake Garda between the 1960s and the 1970s. The successive establishment was hypothesized to be linked to the increase of nutrients following the economic development of the region, and to the high warming documented in this lake district. The new recent spread of this species in Southern Europe emphasizes the ecological heterogeneity and the possible existence of ecotypes, confirmed by the recent discovery of strains showing high temperature optima for growth. In this work, the biogeography and characteristics of strains isolated in different European climatic regions were carried out by adopting a multidisciplinary approach. A phylogenetic study of the 16S rRNA and rpoB genes was integrated with the assessment of the toxic potential by PCR and LC-MS. The study will contribute to identify better management options aimed to mitigate the effects of this new cyanobacterium on the large subalpine lakes.