Using diatoms to assess river restoration: A pilot study inWhychus Creek, Oregon,USA

A primary goal of river restoration is to reestablish lost ecological functions. Yet the impact of restoration on diatom assemblages and algal biomass in a stream is rarely addressed in the scientific literature reporting the outcomes of restoration projects aimed at improving riverine habitat. To investigate the potential for using benthic diatoms as indicators of the benefits to habitat associated with river restoration, we conducted a pilot diatom study in Whychus Creek, a headwater tributary of the Deschutes River in Oregon, USA. As part of a work study project for college students, we collected periphyton samples in a restored reach, a restored transition reach and an unrestored reach (control) and compared diatom assemblages and algae biomass of these reaches. Diatom assemblages and traits differed substantially between the control and restored reaches and the median percentage of chlorophyllain the periphyton biomass increased from 9% in the control reach to 12% in the restored reach. The results of this pilot study suggest that benthic diatom assemblage may be useful indicators of river restoration success, particularly for approaches that aim to reconfigure channels and increase floodplain connectivity and habitat complexity.