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ASSOCIATION AMONG INVERTEBRATES AND HABITAT INDICATORS FOR LARGE RIVERS IN THE MIDWEST
Citation:
Flotemersch, J E., K A. Blocksom, J J. Hutchens, AND B C. Autrey. ASSOCIATION AMONG INVERTEBRATES AND HABITAT INDICATORS FOR LARGE RIVERS IN THE MIDWEST. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-04/177 (NTIS PB2006-114610), 2004.
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:
Six reaches in each of two large rivers (one each in Kentucky and Ohio) were sampled using a prototype benthic macroinvertebrate sampling technique. The intent was to better understand the relationship between large river macroinvertebrate assemblages and habitat features. This information was to determine an acceptable sampling design to support development of a large river bioassessment protocol (LR-BP). Specific objectives included determining the appropriate number of habitat point-samples to be collected, examining how varying reach length affects assemblage characteristics, and determining an appropriate laboratory subsample size to accompany the resulting field sampling method. At each site, both banks of 12 transects separated by increasingly larger distances were sampled. Analyses were conducted using Monte Carlo methods. Interpretation of results relied on the metric values of total taxa richness, mayfly taxa richness, caddisfly taxa richness, Diptera richness, % mayflies, % caddisflies, % Tanytarsini, % non-Tanytarsini dipterans and non-insects, and % tolerant individuals.
This research indicates that, using the sampling technique discussed herein, a representative sample of the benthic macroinvertebrate fauna in the study reaches was collected by sampling both banks of 6 transects spaced at 100 m intervals over a 500-m distance. It is hypothesized that these results were achieved because the sampling method and design effectively sampled the benthic macroinvertebrate fauna of the dominant habitat types within the reach.
It is recommended that the field method be coupled with a fixed laboratory subsample size of 300 organisms for bioassessment purposes, with the recognition that a subsample size of 500 organisms may be needed to meet the objectives of some studies. This recommendation is based on the response of the tested metrics, and the observation that the ability to separate sites of different macroinvertebrate composition generally did not increase with larger subsample sizes. It is likely this approach will over-sample sites of uniform composition, but the goal was to develop a standardized LR-BP that would perform well across sites of differing habitat composition. It should be noted that the LR-BP for macroinvertebrates has only been tested in main-channel habitats. It may work equally well on off-channel habitats, but this remains to be tested.
While the method has been designed to perform well in a variety of habitats, resulting data should be interpreted with appreciation for coarse habitat characteristics. This information would ideally be derived from habitat data collected concomitantly with the faunal data. Sites can then be categorized into river types (e.g., impounded vs. free-flowing or lowland vs. upland rivers) or even habitat types within a specific river (e.g., sandy- vs. cobble-bottom) in a more controlled environment (i.e., in the laboratory), thus increasing the overall integrity of any and all site assessments. Possible modifications to the method to streamline its future application in the field are provided.