Elucidating taxonomic and functional differences between the presence and activity of the microorganisms that inhabit the phycosphere of Microcystis spp. blooms.

Abstract

As it is well known, the constant climate warming and eutrophication of water bodies, had led to an increase in cyanobacterial blooms worldwide, especially from the Microcystis genus. Due to the nature of Microcystis colonies, which are surrounded by a mucilaginous layer populated by microorganisms, knowing about the interplay between the cyanobacteria and their microbiome, the role of each partner in Microcystis dynamics and their evolutionary history is useful for bloom management and prediction. With that in mind, in this study we evaluate if the heterotrophic bacterial community structure corresponded with the active taxa using 16S gene metabarcoding of gDNA and cDNA, respectively, of a size fractionated sample taken from a site within the Salto Grande reservoir in the Uruguay River during a Microcystis spp. bloom. Firstly, it was seen that the diversity was higher in the smallest fractions than in the largest ones, and that was accompanied by a decrease in activity of the majority of taxa. Also, a very interesting fact was that besides it was definitely a Microcystis bloom (microscopic images, not shown), when the data was analyzed Microcystis was not the most abundant taxon, and did not even reach 15%, but was the most active one. This study is a novelty mainly because of the data generated related to activity (cDNA), which was never done before for this kind of sample.