Bioassessment of Stream‐Water Quality Using Benthic and Planktonic Algae Collected Along an Urban Intensity Gradient in the Eastern Cornbelt Plains Ecoregion, Ohio, USA

Abstract

AbstractAlgae possess many attributes that make them ideal organisms to employ in water‐quality investigations. They are ubiquitous, ecologically important, and sensitive to a broad range of stressors; moreover, they respond rapidly to changes in water quality. As part of the USGS National Water Quality Assessment (NAWQA) Program, two methods of analyzing stream‐dwelling algae were used to assess relations among nutrient concentrations, algae, and overall biological integrity of streams along a gradient from agricultural to urban land cover. One method is based on algal production (chlorophyll a, biomass, and 48‐h measures of dissolved oxygen), whereas the other is based on algal community assemblages (species abundance, biovolume, and autecology). Quantitative periphyton and phytoplankton samples were collected from 30 stream reaches in small watersheds (drainage area 7.7–188.7 km2) in south‐west Ohio, during July 2000. Phytoplankton Chl a ranged from 0.5 mg/L in an urban area to 43 mg/L in an agricultural basin, whereas the epilithic periphyton Chl a ranged from 2 mg/m2 in an urban area to 142 mg/m2 in an agricultural basin. Spearman correlations were used to indicate relations between the physical, chemical, and biological factors and measures of algal production. Multivariate analysis of algal species abundance and metrics will be used to characterize gradients of algal community response relative to chemical and landscape factors. Results will be discussed in relation to the influence of urban land‐use intensity and the US Environmental Protection Agency nutrient criteria proposed for this region. The extent to which the algal production and community structure results are useful for bioassessment of stream health will be evaluated with regard to understanding community responses to organic enrichment, dissolved oxygen, specific conductance, light availability, pesticide concentrations, and the monitoring of watershed management practices.