Development of the Water Quality Index (WQI) to assess effects of basin-wide land-use alteration on coastal marshes of the Laurentian Great Lakes

Abstract:

Water-quality impairment for many coastal wetlands of the lower Great Lakes has been attributed to nutrient and sediment inputs from agricultural and urban landscapes, although for some marshes, point-source pollution from municipal or industrial waste- treatment facilities and carp bioturbation have played an equally important role. Regardless of the pollution source, however, the resulting eutrophic and turbid conditions generally lead to a higher biomass of benthic algae, which can reduce the species richness of submergent plants, and which can in turn affect the species richness, species composition and size structure of higher trophic levels (i.e. zooplankton, benthic invertebrates and fish). A direct link should exist between basin-wide land use (e.g. percentage forested, agricultural and urban land) and water-quality conditions in coastal wetlands — although this assumption has not been tested rigorously at a lake-wide scale of all five Great Lakes. In this paper, I will use water-quality data collected from 110 widely distributed wetland complexes to develop a “Water Quality Index” (WQI) that can be used to directly test this assumption.