Aquatic microbial community structure and function across a gradient of logging, fire, and industrial watershed disturbance.

Abstract

The role of microbial communities in the recovery of aquatic ecosystems from watershed disturbance has received little attention despite their important role in energy and nutrient cycling. This study investigates the structure and function of microbial communities on a standardized substrate (alder leaves) in small streams across a wide gradient of watershed disturbances. Microbial communities exhibited variation with disturbance regime with lower hydrolase enzyme activities at all disturbed streams compared to undisturbed streams, and the lowest rates of microbial decomposition, fungal biomass, and differences in microbial community composition at the most severely disturbed streams. Forest and wetland cover were identified as important watershed features that provide DOC to fuel microbial activity in aquatic ecosystems. Increasing road density within the watershed was identified as having a negative impact or association on microbial activity that appeared to be linked to inputs of inorganic solutes that were measured through increased levels of specific conductance in stream water samples. This study is one of the first of its kind and it provides some important evidence that leaf litter associated microbial communities can be influenced by factors linked to watershed disturbance and as such may be useful as indicators of watershed disturbance and potentially the state of recovery of aquatic ecosystems.