Environmental Monitoring & Assessment Program

Valerie Brady 1, Jeff Schuldt 2, Lucinda Johnson 1, Jan Ciborowski 3, George Host 1, Tom Hollenhorst 1, Carl Richards 4, Dan Breneman 1 and Joseph Gathman 3

1Natural Resources Research Institute, University of Minnesota Duluth
2University of Wisconsin-Superior
3University of Windsor, Ontario
4Minnesota Sea Grant, Duluth, Minnesota

Identification of reference conditions for large, heterogeneous geographic areas poses a challenging problem. We developed a mechanism for characterizing disturbance in Great Lakes coastal wetlands using readily-available remotely sensed data. Within Ecological Sections bordering the US Great Lakes coast, coastal wetlands were separated into three classes: open coastal marshes, river-influenced wetlands, and protected wetlands. Degree of anthropogenic disturbance in contributing areas to these wetlands was assessed using a 'watershed' approach in which disturbance was summarized for each watershed. Watersheds were delineated in GIS using elevation data. Cumulative distributions of each variable were used to rank wetland polygons based on minimal levels of disturbance across all axes. A final ranking of polygons >4 ha was used to identify candidate reference areas for each wetland type in each Ecological Section. Fish communities were characterized for both reference and non-reference wetlands to test whether the communities from reference wetlands were distinct from those in non-reference wetlands. Non-reference wetland sites were selected across a disturbance gradient created using principal components analysis to summarize the influence of 214 GIS-based environmental and human disturbance variables for shoreline areas across the Great Lakes basin. Both reference and non-reference wetlands were sampled concurrently using the same teams and methods. The resultant fish community data allowed us to establish benchmarks (values and confidence intervals) that reflect the "best attainable" (i.e. least disturbed) fish community for each Great Lakes coastal wetland type in each Ecological Section.

Keywords: reference condition, least disturbed, fish community, benchmark, wetland