Acute salt stress promotes altered assembly dynamics of nascent freshwater microbial biofilm communities

Freshwater ecosystems are under increasing threat of salinization due to human activity. Given the contributions of microbial communities to stream ecosystems, it is critical to understand how these communities are affected by the increasing presence of salt in the environment. We investigated how salt concentrations representing the 95th- and 99th-percentile of concentrations observed in NE Ohio streams affect bacterial community succession and what implications this has on community-level functional capabilities. We observed considerable structural changes in bacterial composition among treatments that corresponded with niche expansion by more salt-tolerant taxa. Increases in denitrification gene abundances and modifications to extracellular enzyme activity were also observed. These data suggest that continued salt pollution can dramatically affect community structure and has the potential to modify the functional contributions of the bacterial community to the ecosystem.