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Development of a regional macroinvertebrate index for large river bioassessment
Citation:
BLOCKSOM, K. A. AND B. R. JOHNSON. Development of a regional macroinvertebrate index for large river bioassessment. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 9(2):313-328, (2009).
Impact/Purpose:
The objective of this research is to support the Office of Water’s goals under the Clean Water Act, address the specific recommendations of the National Research Council for integrated watershed research, and contribute to the USEPA's "Environmental Indicators Initiative" to improve the Agency's ability to report on the status of and trends in environmental conditions and their impacts on the nation's natural resources. Task 8734 supports research to characterize the condition of aquatic resources and responses of aquatic assemblages and ecosystem processes to anthropogenic disturbance. These methods and indicators will be applied at multiple spatial and temporal scales. They will be evaluated for their statistical properties and their ability to detect specific stressors, mixtures, landscape and riparian measures of watershed disturbance, and early indicators of restoration and recovery. 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:
Large river bioassessment protocols lag far behind those of wadeable streams and often rely on fish assemblages of individual rivers. We developed a regional macroinvertebrate index and assessed relative condition of six large river tributaries to the upper Mississippi and Ohio rivers. In 2004 and 2005, benthic macroinvertebrates, water chemistry and habitat data were collected from randomly selected sites on each of the St. Croix, Wisconsin, Minnesota, Scioto, Wabash and Illinois rivers. We first identified the human disturbance gradient using principal components analysis (PCA) of abiotic data. From the PCA, least disturbed sites showed strong separation from stressed sites along a gradient contrasting high water clarity, canopy cover, habitat scores and plant-based substrates at one end and higher conductivity and nutrient concentrations at the other. Evaluation of 93 benthic metrics identified those with good range, responsiveness and relative scope of impairment, as well as redundancies with other metrics. The final index was composed of Ephemeroptera taxa richness, chironomid taxa richness, % chironomids taxa, Hilsenhoff's Biotic Index (HBI), swimmer taxa richness, predator taxa richness and % scraper taxa. Each of the selected metrics was scored using thresholds based on all sites, and averaging across the seven metric scores, we obtained the Non-wadeable Macroinvertebrate Assemblage Condition Index. (NMACI). The NMACI showed a strong response to disturbance using a validation dataset and was highly correlated with non-metric multidimensional scaling (NMS) ordination axes of benthic taxa. The cumulative distribution function of index scores for each river showed qualitative differences in condition among rivers. NMACI scores were highest for the federally protected St. Croix River and lowest for the Illinois River. Other rivers were intermediate and generally reflected the mixture of landuse types within individual basins. Use of regional reference sites, though setting a high level of expectation, provided a valuable frame of reference for the potential of large river benthic communities that will aid management and restoration efforts.