A test of the variability and usefulness of SOLEC indicators in wetlands of Lakes Huron and Michigan

Introduction Development of indicators of " ecosystem health " for Great Lakes coastal wetlands was recognized as a major need at the State-of-the-Lakes Ecosystem Conferences (SOLEC) held in Buffalo, New York in 1998 and Hamilton, Ontario in 2000. Indicators listed by the wetlands indicators task force at these conferences included indices of biotic integrity (IBI) based on macroinvertebrates, fish and plants. We previously developed and published a macroinvertebrate based bioassessment procedure for fringing coastal wetlands of Lake Huron (e.g. Burton et al. 1999, Kashian and Burton 2000; Uzarski et al., submitted; see summary on the bioassessment wetlands working group (BAWWG) web site attempted to develop wetland IBIs for the upper Great Lakes using macrophytes, fish, and microinvertebrates. Even though some metrics showed promise, they concluded that natural water level changes from those that existed during their data collection were likely to alter communities enough to invalidate metrics in subsequent years. We were able to overcome this problem for fringing coastal wetlands by developing a method based on sampling any or all of four plant zones depending on the number inundated in any particular year (Burton et al. 1999, Uzarski et al., submitted). The IBI scores for a particular year were calculated by summing scores from each zone across the number of zones that were inundated in that year. As water levels decreased and zones were no longer inundated, the IBI scores which indicated the condition of the wetland changed, but metrics for even a single inundated zone proved to be effective in establishing wetland condition (Uzarski et al., submitted). Our system worked well for fringing wetlands of Lakes Huron and Michigan as water decreased by more than one meter from 1997 through 2002. Based on these results, we are confident that our macroinvertebrate IBI is valid under a wide range of water levels (Uzarski et al. submitted). We are also working to develop similar macroinvertebrate based IBI systems for other types of Great Lake systems with particular interest in the drowned river mouth wetlands of eastern Lake Michigan. We are working on fish and plant based metrics that can be adjusted over water level changes and believe that a viable IBI can be developed based on these taxa as well. Minns et al. (1994) applied Karr's approach of using fish as indicators of stream biotic integrity (e.g., Karr 1981, Karr et al. 1986) to marshes of Great Lakes' Areas of …