Abstract ATM-9528062 Johnson, Thomas C. University of Minnesota Title: IDEAL Studies on the Paleolimnology and Paleoclimate of Lake Victoria: fossil invertebrate assemblages as proxies for climatic and anthropogenic change The IDEAL initiative is a multinational effort to study the limnology, modern and past ecology, and paleoclimatology of the large lakes of East Africa. Undisturbed recovery of an in situ sediment profile is a prerequisite for successful paleolimnological study. This award supports the development of deep-water freeze- coring technology to meet the sampling challenges presented by tropical lakes, in particular deep productive lakes where fine stratigraphy can become disrupted in unfrozen core samples by post- recovery degassing of sedimentary methane. The device will be used to collect cores of recent sediments in profundal and sublittoral areas of Lake Victoria, visited during the IDEAL 1996 field campaign. Fitted with a well-constrained 210Pb-chronology, these undisturbed sedimentary archives will permit reconstruction of Lake Victoria's 19th- and 20th century history at the finest temporal resolution possible. Study of the freeze-core samples will focus on natural and anthropogenic changes in species composition of benthic and planktonic invertebrate communities, for which currently no long-term data are available. Analysis of fossil invertebrates in long piston-core records from Lake Victoria collected by IDEAL will produce valuable independent information on the lake's late Quaternary history and help constrain paleoclimatic interpretations based on sedimentology and stable-isotope geochemistry.
