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Development of a regional littoral benthic macroinvertebrate multi-metric index (MMI) for lakes from the National Lakes Assessment
Citation:
Mitchell, R., A. T. HERLIHY, D. V. PECK, J. L. STODDARD, AND J. VAN SICKLE. Development of a regional littoral benthic macroinvertebrate multi-metric index (MMI) for lakes from the National Lakes Assessment. Presented at North American Lake Management Society 30th Annual Symposium, Oklahoma City, OK, November 03 - 05, 2010.
Impact/Purpose:
During the 2007 National Lakes Assessment (NLA) benthic macroinvertebrate samples were collected from the lake littoral zone.
Description:
During the 2007 National Lakes Assessment (NLA) benthic macroinvertebrate samples were collected from the lake littoral zone. The purpose of the sampling was to assess the feasibility of a multi-metric index (MMI) to assess the condition of the littoral benthic macroinvertebrate assemblage. These samples were collected at the 10 physical habitat locations around the lake and then composited into one sample. A D-frame 500-µm mesh dip net was used to collect samples, and sampling was done by swiping the net along the bottom substrate or through vegetation for a total of one meter, within each physical habitat station. A total of 1,045 lakes were assessed and of those 926 were probability-sampled lakes, which were used to assess the biological condition of the littoral zone assemblage. Separate MMIs were developed for the contiguous United States. These regions included, Northern Appalachians (NAP), Southern Appalachians (SAP), Upper Midwest (UMW), Coastal Plains (CPL), Plains (PLN, which include Northern Plains, Southern Plains, and Temperate Plains), and Western Mountains and Xeric (WMX), which represent the aggregate level 3 ecoregions of the United States. Each regional MMI employed one metric from each of the following categories: richness, composition, feeding group, habitat, tolerance, and diversity. Including a metric from each of the different categories ensures that disturbances that may influence the different dimensions of benthic macroinvertebrate assemblages are accounted for in each of the regional MMIs. A reference approach was used to assess the sensitivity of the regional MMIs, and MMIs were selected based on their ability to differentiate reference from impacted sites or reference from intermediate and impacted sites. Results from the regional MMIs showed that the CPL was the most sensitive MMI when comparing reference sites vs. impacted sites, meaning the greatest divergence occurred between reference and impacted sites in this region. When comparing reference to the intermediate and impacted sites, the PLN region showed the greatest divergence among the three site types. The region with the least sensitive MMI occurred in the UMW for both comparison, and one possible reason for this is that there was less divergence between the high quality and impacted sites of this region, compared with other parts of the country. However, this finding may also be influenced by the number of missing data points from the survey which limits the ability of the analysis to assess all lakes in this region’s population of lakes, as is shown by the large percentage of lakes that could not be assessed in this region (~24% not assessed). The regions with the greatest number of lakes in good condition occurred in the WMX, UMW, and NAP, and the PLN region had the lowest percentage of lakes in good condition.