The structure of bacterial metacommunities in river networks results from the balance between dispersal (mostly from upstream or from the nearby land) and environmental selection of local communities. Temporary river networks experience hydrological phases of drying and rewetting which may interfere in the dispersal and species sorting processes between habitats. We investigated the structure of river bacterial assemblages (through amplicon sequencing of the 16S rRNA gene) colonizing streambed sediments and floodplain habitats (4 different habitat types) in two river reaches (Permanent vs Intermittent) differing in their hydrology during 4 hydrological periods (encompassing the expansion, contraction, fragmentation, and non-flow phases). Our results indicate that environmental selection was the major structuring mechanism of sediment bacterial communities. We found high species turnover across habitats permanently and intermittently connected by water flow. Local communities were filtered by the specific environmental features of each habitat type. Isolated pools, for instance, favored habitat specialists within several exclusively bacterial taxa from aquatic habitats, while drying areas favoured the occurrence of taxa of terrestrial origin. Given that climate change is increasing the duration of drying periods, we may expect a future homogenisation of bacterial communities, corresponding to the lower duration of aquatic habitats.

Primary Presenter: Anna Freixa, Catalan Institute for Water Research (ICRA) (afreixa@icra.cat)

Authors:

Anna Freixa, Catalan Institute for Water Research (ICRA)  (afreixa@icra.cat)

Juan González-Trujillo, Museo Nacional de Ciencias Naturales (CSIC-MNCN)  (jdgonzalezt@unal.edu.co)

Sergi Sabater, Catalan Institute for Water Research (ICRA)  (ssabater@icra.cat)