Lakes in many areas of the world now receive considerable inputs of sulfate from acid deposition. Giblin, Peterson, and Fry previously focused on the biogeochemical changes that occur in lakes due to increased sulfate loading. Their work revealed that some of the existing paradigms on how the sulfur cycle in lakes functions may need to be modified. The investigators now have evidence from both laboratory incubations and sediment profiles that carbon limits sulfate reduction in some lakes. in this proposal the investigators focus on several questions that are a direct outgrowth of their previous work. These are: 1) How widespread is carbon limitation of sulfur storage in lake sediments? 2) How does eutrophication influence the amounts and forms of sulfur stored in lake sediments? 3) Does iron availability effect sulfur storage in sediments in many lakes? The investigators propose a multifaceted experimental approach that includes the measurement of sediment element profiles from a variety of lakes, metabolic studies at the whole lake level, and the experimental manipulation of variables in field and laboratory settings. This balanced approach should allow robust conclusions about responses of the C,N,Fe, and P cycles to changes in sulfate loading, and how these responses are altered by eutrophication. This research is being conducted by a highly qualified team from an outstanding institution. The results of this work will provide important knowledge for understanding the responses of lakes to eutrophication and acid precipitation.
