The effects of land-use characteristics and acid sensitivity on the ecological status of Maryland coastal plain streams

A 2-year study was conducted to evaluate the ecological status of 12 acid-sensitive and 12 non-acid-sensitive Maryland coastal plain streams during the spring, summer, and fall of 1992 to 1993. An index of biotic integrity (IBI) for fish, chemical parameters, and physical habitat conditions were evaluated in these streams. Correlations of land-use activities (forested streams vs. agricultural dominated streams) and watershed size were identified in the coastal plain streams with biological, chemical, and physical conditions. These data were also used to determine if a poor IBI for coastal plain stream fish can be related to stream sensitivity from acidic inputs. Physical habitat was more important than water quality in determining IBI values for the 2-year period. Acid sensitivity was also important in influencing the IBI but the influence of acid sensitivity was overshadowed by physical habitat. When variation in physical habitat was accounted for among sites, the IBI in nonacid-sensitive streams was higher than in acid-sensitive streams. Initial results demonstrated that IBI values were higher in agricultural dominated streams when compared to forested streams. Consideration of only two dominant land-use types caused oversimplification of these results because urban land use (often associated with negative effects) was positively correlated with forested streams and negatively correlated with agricultural streams.