Identifying Reference Conditions in Highly Disturbed Coastal Great Lakes Regions

Identification of reference conditions in highly modified landscapes poses a challenging problem. We identified "least disturbed" conditions within Great Lakes coastal wetland basins, based on the degree of anthropogenic disturbances, including road density, agricultural and urban land use, population and point source density. Reference sites were identified for the entire Great Lakes Basin and then uniquely in two ecoregions (the Northern Great Lakes (NGL) and Erie-Ontario Lowlands (EOL)). The reference threshold metric for all NGL wetlands combined was 0.03, while that of the EOL wetlands was 0.37, approximately a 10-fold difference, illustrating the high level of underlying disturbance in the EOL. In the absence of minimally impacted conditions in the EOL, we are evaluating the possible use of reference communities characterized for the entire Basin as an alternative. To eliminate differences due to underlying variation and climate, we included only those fish species that were distributed across the entire Great Lakes Basin. Fish community composition and species traits at EOL reference sites were than compared to those for the entire Basin. Observed versus expected species and traits were related to the human disturbance gradient (HDG) to diagnose potential causes of impairment and assess potential for restoration for the EOL reference wetlands.