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CAN LANDSCAPE CHARACTERISTICS OF WATERSHEDS HELP FIND IMPAIRED ESTUARINE BOTTOM COMMUNITIES
Citation:
Hale, S S., J F. Paul, D McGovern, AND J Heltshe. CAN LANDSCAPE CHARACTERISTICS OF WATERSHEDS HELP FIND IMPAIRED ESTUARINE BOTTOM COMMUNITIES. Presented at ReVA MAIA Conference, King of Prussia, PA, May 13-15, 2003.
Description:
Human alteration of watersheds and their landscapes often leads to undesirable effects in estuaries, such as excess nutrients, organic matter, and sediments, as well as increased levels of contaminants and pathogens. We hypothesized that alterations in watersheds associated with small estuaries (<260 km2) would have strong enough effects to make landscape metrics useful for finding impaired bottom communities. We worked with data for the U.S. Mid-Atlantic coastal plain from Delaware Bay to Chesapeake Bay, where we had 58 pairs of small estuaries and watersheds that spanned wide ranges of land use and land cover. We considered 29 landscape metrics as potential explanatory variables. We used logistic regression models to calculate the probabilities of degraded benthic environmental quality (BEQ), defined by chemical parameters, and impaired estuarine bottom communities, defined by a benthic index and by the total number of bottom-dwelling species. A model using landscape metrics correctly classified BEQ in 90% of the cases; low benthic index and low total number of bottom species were each associated with degraded BEQ (p < 0.01 in a t-test). The logistic regression models for benthic index and total number of species also had excellent discriminatory power (areas under ROC curve of 0.81 and 0.85). Watersheds with higher percentages of urban and agricultural land uses were associated with low benthic index and low total number of species, while those with higher percentages of wetlands were associated with high numbers.