Planktonic microbial communities from microbialite‐bearing lakes sampled along a salinity‐alkalinity gradient

Abstract

Abstract Continental freshwater systems are particularly vulnerable to environmental variation. Climate change‐induced desertification and the anthropogenic exploitation of hydric resources result in the progressive evaporation and salinization of inland water bodies in many areas of the globe. However, how this process impacts microbial communities and their activities in biogeochemical cycles is poorly known. Here, we take a space‐for‐time substitution approach and characterize the prokaryotic and eukaryotic microbial communities of two planktonic cell‐size fractions (0.2–5 μ m and 5–30 μ m) from lakes of diverse trophic levels sampled along a salinity‐alkalinity gradient located in the Trans‐Mexican Volcanic Belt (TMVB). We applied a 16S/18S rRNA gene metabarcoding strategy to determine the microbial community composition of 54 samples from 12 different lakes, from the low‐salinity lake Zirahuén to the hypersaline residual ponds of Rincón de Parangueo. Except for systems at both extremes of the salinity gradient, most lakes along the evaporation trend bear actively forming microbialites, which harbor microbial communities clearly distinct from those of plankton. Several lakes were sampled in winter and late spring and the crater lakes Alchichica and Atexcac were sampled across the water column. Physicochemical parameters related to salinity‐alkalinity were the most influential drivers of microbial community structure whereas trophic status, depth, or season were less important. Our results suggest that climate change and anthropogenic‐induced hydric deficit could significantly affect microbial communities, potentially altering ecosystem functioning.