HAMBROOK, JULIE A. U.S. Geological Society, 6480 Doubletree Ave., Columbus, OH 43229-1111. - Bioassessment of stream-water quality using benthic and planktonic algae collected along an urban intensity gradient in the Eastern Cornbelt Plains Ecoregion, Ohio, USA.
Algae 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-hour 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 to 188.7 km2) in southwest 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 U.S.
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.
Key words: bioassessment, Ohio, periphyton, phytoplankton, streams, urban intensity gradient