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

Abstract

Continental freshwater systems are particularly vulnerable to environmental variation. Climate changeinduced 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-fortime substitution approach and characterize the prokaryotic and eukaryotic microbial communities of two planktonic cell-size fractions (0.2-5 μm and 5-30 μm) 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 Rinc on 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.

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

“…It could also be argued that large OM particles in Alchichica for example (Ardiles et al, 2012) favor the sedimentation of OC rather than DOC production, thereby favoring the oxygenation of deep waters as suggested for the beginning of the Phanerozoic period with advent of eukaryotic plankton (Lenton and Daines, 2018;Fakhraee et al, 2021). Yet, plankton of the studied Mexican lakes is overall dominated by prokaryotic communities and not large organisms (Iniesto et al, 2022). Besides, rapid sinking of OM particles in modern oceans does not necessarily preclude important fluxes of benthic DOC from the sediments (around ~ 100 PgC.yr -1 in today's ocean; Burdige and Komada, 2015) and especially in anoxic bottom waters (Dadi et al, 2017).…”

“…5a). Some purple sulfur bacteria (anoxygenic phototrophs belonging to the Proteobacteria) have been identified but they become significant towards the end of the stratification (from July/August to December/January; Alcántara-Hernández et al, 2022;Iniesto et al, 2022).…”

“…Vilaclara et al, 1993;Zeyen et al, 2021) and isotopic compositions of dissolved inorganic and particulate organic carbon (DIC, POC) measured in the same lakes (Havas et al, submitted). The four lakes exhibit distinct water chemistries aligning along an alkalinity/salinity gradient (Zeyen et al, 2021) and diverse planktonic microbial communities (Iniesto et al, 2022;Havas et al, submitted). This allows us to examine the effect of specific environmental and ecological constraints on the DOC reservoir, and how this latter influences the overall C cycle in redox-stratified environments.…”

Single-cell transcriptomics reveals functional insights into a non-model aquatic phytoflagellate and its metabolically linked bacterial community

“…They exhibit a varied catalogue of gene expression quirks, such as mRNA fragmentation, trans ­splicing or translational slippage (Smith and Keeling 2016). They are ubiqui­tous across various aquatic and terrestrial environments (Geisen et al 2015, 2016, Pernice et al 2016), ranging from freshwater to extreme habitats (Iniesto et al 2022, Jamy et al 2022), tropical to polar (Marshall and Laybourn-Parry 2002, Mahe et al 2017), and are furthermore subject to very strong spatial (Forster et al 2016) and seasonal constraints (Moreira and Lopez-Garda 2019, Vass et al 2020). The unifying feature that groups them together, beyond their eukaryotic character, is that they are single celled and, therefore, microscopic.…”