9416810 Magnuson This project encompasses three international efforts on the long-term temporal and spatial dynamics of temperate lakes at regional to global scales. Three questions are addressed with data from widely scattered, multiple lake districts. These questions are: 1. What patterns occur in ecological variability and organization of lake ecosystems when lake districts are considered at regional and global scales? 2. Can patterns of gains and losses of species from individual lakes be related to the overall patterns of species occurrence for lakes within a region? 3. Can analyses of lake ice freeze and breakup phenologies around the globe be used to describe and understand large scale dynamics and trends in climate? The study of ecological variability and organization of lake districts will examine temporal variability patterns (conherence) of lakes within lake districts, explore the relationship between landscape position and lake variability across lakes in different lake districts, and examine relations between lake variability and factors such as lake morphometry and land use. Comparisons will provide opportunities to determine whether patterns observed at the Northern Highland Lake District occur across lake districts worldwide. The analyses of gains and losses of fish and zooplankton species will investigate regional dynamics of species gains, losses, and turnover rates in different lake districts, relate these dynamics to the extent and strength of interconnections among lakes within these regions, and investigate how human activities may influence these processes. The analyses of lake ice phenology, climate change, and variability in the Northern Hemisphere, will analyze interannual variability in thaw and freeze dates and where possible the antecedent climatic variability. Are observed patterns in Wisconsin general for larger regions of the northern hemisphere? Patterns are the recent warming based on breakup dates, and variabili ty associated with ENSO events and inderdecadal or longer time scales. Expected patterns will be generated through global climate and ice freeze modeling.
