Understanding the impacts river basin development has on rivers in northern Michigan.

Abstract

Two rivers located in Northern Michigan were compared to determine the impact of development on nutrient concentrations and limitation, macroinvertebrate communities, and habitat composition. One river (Little Black River) experienced agricultural impacts as well as the impacts of a played golf course, while the other (Carp Lake River) experienced much less direct development. Habitat mapping, macroinvertebrate collection, nutrient data, nutrient limitation data, discharge and water chemistry data were all compared between the two rivers. Our habitat mapping showed the substrate of Little Black River to be composed of predominantly clay, posing a large confounding factor within our research. In the Little Black River there was a very low EPT index (7%) compared to that of Carp Lake River (79%). We also found Carp Lake River to be co-limited by nitrogen and phosphorus (F=5.368, df=1, P=0.034), and Little Black River to be limited by nitrogen (F=5.368, df=1, P=0.034). The clay substrate in the Little Black River seemed to increase the turbidity of the river, and decrease light penetration to the river bottom. This showed lower levels of periphyton growth than those found in Carp Lake River. The low EPT index shows low water quality in Little Black River compared to Carp Lake River. Additionally, the nutrient limitation in Little Black River can show that there is less nutrient limitation than there is in Carp Lake River. This led to the conclusion that the Little Black River is impacted by the development observed along the river basin when compared to Carp Lake River.