Saline inland waters are ubiquitous in arid and semi-arid regions and host a very unique ecology and biogeochemistry. Yet, how salinity shapes the structure and functioning of aquatic microbial communities in these systems remains elusive. Here, we investigated the diversity and functioning of bacterioplankton communities in shallow lakes and ponds across a wide range of naturally occurring salinity levels, from freshwater to hypersaline systems (specific conductivity ranging from 0.2 to >150 mS/cm). We characterized the diversity of the total (DNA-based) and active (RNA-based) community members and combined these genetic data with community-level metabolic profiles, extracellular enzymatic activities, and in situ organic carbon degradation essays. Bacterioplankton compositional differences across sites strongly aligned with the salinity gradient, indicating that salinity exerts a major environmental filtering on the community assemblages. Despite showing high bacterial abundance, communities in more saline systems had lower taxonomic and functional diversity, which translated into less diverse metabolic profiles (higher specialization) and lower carbon degradation rates. Altogether, our results provide new insights into the processes that shape bacterioplankton community assembly in saline lakes and may help anticipate how freshwater ecosystems willrespond to salinization in the mid-long term.

Primary Presenter: Joan Casas-Ruiz, University of Girona (jpcasasruiz@gmail.com)

Authors:

Joan P. Casas-Ruiz, GRECO, Intitute of Aquatic Ecology, University of Girona  (jpcasasruiz@gmail.com)

Joan Ferriol, GRECO, Intitute of Aquatic Ecology, University of Girona  (joanferriol98@gmail.com)

Anna Doménech-Pascual, GRECO, Intitute of Aquatic Ecology, University of Girona  (a.domenech@udg.edu)

Lluís Bañeras, Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona  (lluis.banyeras@udg.edu)

Núria Perujo, UFZ Helmholtz Centre for Environmental Research  (nuria.perujo.buxeda@gmail.com)

Dani Vall-llosera, GRECO, Intitute of Aquatic Ecology, University of Girona  (danvallllosera@gmail.com)

Andrea Butturini, Department de Biologia Evolutiva, Ecologia i Ciencies Ambientals, Universitat de Barcelona  (abutturini@ub.edu)

Anna M. Romaní, GRECO, Intitute of Aquatic Ecology, University of Girona  (anna.romani@udg.edu)