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A COMPARISON OF BENTHIC MACROINVERTEBRATE SAMPLING METHODS ON SELECTED LARGE RIVER TRIBUTARIES TO THE MISSISSIPPI
Citation:
JOHNSON, B. R. AND K. A. BLOCKSOM. A COMPARISON OF BENTHIC MACROINVERTEBRATE SAMPLING METHODS ON SELECTED LARGE RIVER TRIBUTARIES TO THE MISSISSIPPI. Presented at SWIMS Conference , Chicago, IL, January 30 - February 01, 2007.
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:
We compared three benthic macroinvertebrate sampling methods on the St. Croix, Wisconsin and Scioto Rivers in summer 2004 and 2005. EPA's newly developed, multi-habitat Large River Bioassessment Protocol (LR-BP) was compared to the multi-habitat method of the Minnesota Pollution Control Agency (MPCA) and to Hester-Dendy artificial substrates (H-D). Results indicated large differences between the LR-BP and the other sampling methods and that method differences outweighed differences among rivers. The LR-BP generally collected the most taxa and tended to include more chironomids and tolerant taxa than either the MPCA or H-D methods. In the laboratory, 500 organisms were sorted randomly from each sample and richness metric values were calculated and evaluated across a range of fixed-count subsample sizes (100 to 500 organisms). Regardless of field method, richness metrics changed little (<12%) at subsample sizes of >300 individuals, suggesting a 300 fixed count may be an appropriate level of laboratory effort for large river bioassessment. Addition of a large rare sort also increased metric values similarly among field methods, though increases were greatest for the MPCA method. Results of this study indicate that artificial substrates or richest targeted habitat approaches, such as MPCA, may underrepresent some components of the benthic community that might be valuable for biological assessment of large rivers.