Multi-scale approaches for quantifying effects of multiple stressors in aquatic ecosystems

Aquatic ecosystems are influenced in a hierarchical fashion by the climate and landform in which they are embedded, by land use and land cover in the catchment and the immediate vicinity, and by ecosystem-scale factors.  Quantifying organismal and ecosystem responses to the multiple and interacting effects of human activities requires a multi-pronged approach.  We have investigated the effects of land management and climate change on wetland ecosystems, amphibian community, and organismal health using such an approach.  Data from laboratory and mesocosm experiments, intensive field studies, and extensive field campaigns spanning the upper Midwest have been assembled.  In this presentation we will address the advantages of this multi-pronged approach and will focus on two case studies:  1) quantifying indirect effects of the chemical atrazine on ecosystem properties and subsequently, amphibian immune responses and health; and 2) quantifying effects of climate change and landscape pattern on persistence of amphibian populations.  Lessons from these investigations emphasize the potential for subtle direct and indirect effects of chemicals on biota and the need to incorporate data from multiple study types to address such issues.  Landscape attributes including wetland density and distribution also must be considered when planning, implementing, and refining restoration and conservation activities in light of changing climate.