Impacts of climate change on aquatic ecosystem functioning and health

We review published analyses of the effects of climate change on goods and services provided by freshwater ecosystems in the United States. Climate-in duced changes must be assessed in the context of massive anthropogenic chan ges in water quantity and quality resulting from altered patterns of land u se, water withdrawal, and species invasions; these may dwarf or exacerbate climate-induced changes. Water to meet instream needs is competing with oth er uses of water, and that competition is likely to be increased by climate change. We review recent predictions of the impacts of climate change on a quatic ecosystems in eight regions of North America. Impacts include warmer temperatures that alter lake mixing regimes and availability of fish habit at; changed magnitude and seasonality of runoff regimes that alter nutrient loading and limit habitat availability at low flow; and loss of prairie po thole wetlands that reduces waterfowl populations. Many of the predicted ch anges in aquatic ecosystems are a consequence of climatic effects on terres trial ecosystems; shifts in riparian vegetation and hydrology are particula rly critical. We review models that could be used to explore potential effe cts of climate change on freshwater ecosystems; these include models of ins tream flow, bioenergetics models, nutrient spiraling models, and models rel ating riverine food webs to hydrologic regime. We discuss potential ecologi cal risks, benefits, and costs of climate change and identify information n eeds and model improvements that are required to improve our ability to pre dict and identify climate change impacts and to evaluate management options .