Wednesday, August 8, 2007 - 3:40 PMOOS 28-7: Protozoan assemblage dynamics in headwater streams: A potential water-quality bioassessment tool
Deborah K. Hersha and Lance R. Williams. The Ohio State University
Landuse degradation, predominantly agricultural, profoundly impacts headwater stream integrity because of the tight interface between the landscape (<5 mi2 drainage area) and stream channel. Anthropogenic influences may be readily expressed in the local region, as well as the downstream watershed compartments. A protozoan bioassessment tool may augment commonly-used, and often unstable, biological indicators (fish, macroinvertebrates, and salamanders) in intermittent headwater stream assessment. Twenty-four 100m reaches impacted by a landuse gradient of woodlots, urbanization, feedlots, and agriculture were identified in two subwatersheds, across two ecoregions in the Sugar Creek, Ohio watershed. Two seasonal, protozoan sample sets (including abiotic parameters) were collected on colonizing, benthos-surface contact polyurethane foam units. Protozoan abundance, diversity, and assemblage composition were microscopically assessed live within 24 hours after extraction. Indication of impacted water quality obtained via protozoan bioassessment “signatures” were analyzed using a multivariate statistical procedure. Protozoan assemblage composition clustered in response to the headwater stream’s impact gradient and across ecoregions. A community shift of microbial organisms from those responsible for primary production (e.g., algae) to those predominately responsible for secondary production (e.g., nanoflagellates and ciliates) was apparent in the highly impacted stream reaches. A strong relationship between the protozoan candidate metrics and land use parameters (the apparent driving force within this system) were evident. A protozoan bioassessment tool may provide a more accurate assessment of water quality under certain conditions in headwater streams. Use of this tool offers quantitative evidence that influences and supports effective restoration and/or management practices in promoting ecosystem sustainability.