Alfa and beta diversity of planktonic and periphytic cyanobacteria based on 16S rRNA gene in a subtropical lake system: How similar are they?

Cyanobacteria are an abundant component of both free-living (phytoplankton) andsurface-attached (periphyton) freshwater communities. Despite this, it remainsunknown whether planktonic and periphytic cyanobacteria are structured by the sameecological processes. Here, we explored the distribution of planktonic and periphyticcyanobacteria diversity, based on 16S rRNA gene, in a subtropical lake system.Variation partitioning analysis was employed to determine the influence ofenvironmental (water conditions) and biotic (abundance of heterotrophic bacteria)variables on the cyanobacteria variation. We found that periphytic assemblagesshowed a richness about three times higher than the planktonic ones, highlighting theimportance of the periphytic community to the overall diversity in subtropical lakes. Thepicocyanobacteria Synechococcus was the dominant component of the plankton, ataxon often underestimated using classical methods of quantification (e.g. opticalmicroscopy). Species replacement was the major component explaining the distributionof diversity in both planktonic and periphytic assemblages. However, while planktoniccyanobacteria was primarily influenced by water conditions, periphytic cyanobacteriawas influenced only by the abundance of heterotrophic bacteria. Together, our findingsshowed that assemblages of planktonic and periphytic cyanobacteria are distinct,suggesting a high habitat specialization, and the importance of environmental filteringand biotic interactions in structuring planktonic and periphytic cyanobacteriadistribution, respectively.