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USE OF MACROINVERTEBRATE METRICS TO DIFFERENTIATE BETWEEN THE EFFECTS OF DECREASED CANOPY AND INCREASED EMBEDDEDNESS IN STREAMS IN DRAINING AGRICULTURAL CATCHMENTS
Citation:
Griffith, M. B., F B. Daniel, AND J M. Lazorchak. USE OF MACROINVERTEBRATE METRICS TO DIFFERENTIATE BETWEEN THE EFFECTS OF DECREASED CANOPY AND INCREASED EMBEDDEDNESS IN STREAMS IN DRAINING AGRICULTURAL CATCHMENTS. Presented at North American Benthological Society, Pittsburgh, PA, May 28-June 1, 2002.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Reduced canopy as a result of lost riparian vegetation and increased substrate embeddedness as a result of greater inputs of the fine sediments are two environmental stressor gradients that often covary in streams draining agricultural catchments. An understanding of relationships between these stressors and different macroinvertebrate metrics is needed to select metrics used to diagnose the relative importance of these stressors affecting stream biotic integrity. We used multiple regression to assess relationships between canopy cover, embeddedness, and macroinvertebrate metrics at 35 sites on tributaries of the Little Miami River. The small catchments in this basin are characterized by variable land cover by row crop agriculture (23-91%), and the basin includes two Level IV ecoregions (Loamy, High Lime Till Plains and Pre-Wisconsinan Drift Plains) that vary in land slope and soil characteristics. We identified macroinvertebrate metrics that specifically varied in relation to embeddedness: number of relative abundance of EPT taxa, of Ephemeroptera taxa or of Trichoptera taxa, relative abundance of noninsects, of oligochaetes and leeches, of tolerant or facultative taxa, and Hilsenhoff's Biotic Index. The relationship for some metrics varied with ecoregion. No tested metrics correlated well with canopy cover. In this region, substrate embeddedness appears more important in affecting macroinvertebrate assemblages.