Environmental Change and Responses in East African Lakes

About this book

The International Decade for the East African Lakes (IDEAL) has completed its first phase of field studies, and has assembled in this volume its findings, ranging from seismic reflections to historical drought chronologies, geochemistry, and modern food web processes. Multidisciplinary IDEAL investigations are summarized and integrated, revealing that modern changes in the East African lakes share a continuity with past variations in climate and environmental conditions. Results from an array of disciplinary perspectives and evidentiary lines point to the causative role of modern climate variation in the deterioration of Lake Victoria, one of the most prominent lakes on the planet. The ancient conditions of Victoria and other East African lakes are reconstructed with forensic tools that permit measurements of paleomagnetism, pollen and algal fossils, biogenic minerals, depositional carbonates, and bulk geochemistry. Oral traditions, explorer's journals, and records of the ancient Nile provide human testimonies that parallel the physical record. Studies of biological production, nutrient dynamics, and lower food web processes reveal how the lake communities function at the trophic levels that leave sedimentary evidence in the form of organic matter, minerals, and fossils. Comparisons of weather records and lake properties demonstrate a striking change in climate conditions during the present century with causal links to lake conditions.

The collected scientific perspective makes a compelling case for the worth of integrated studies across a spectrum of traditional specialties when they are focused on complex environmental issues.

Contents

History and Ontogeny of IDEAL; D.A. Lehman. Investigations of Lake Victoria. Climate, History and Modern Dynamics. Historical Fluctuations of Lake Victoria and Other Lakes in the Northern Rift Valley of East Africa; S.E. Nicholson. Ancient Analogues for Recent Environmental Changes at Lake Victoria, East Africa; J.C. Stager. Initial Results of 1995 IDEAL Seismic Reflection Survey of Lake Victoria, Uganda and Tanzania; C.A. Scholz, et al. Environmental Magnetism of the Late Pleistocene/Holocene Sequences from Lake Victoria, East Africa; G.N. Ngobi, et al. Biogenic Silica Profiles in Holocene Cores from Lake Victoria: Implications for Lake Level History and Initiation of the Victoria Nile; T.C. Johnson, et al. Role of Apatite Weathering in the Eutrophication of Lake Victoria; J. Holtzman, J.T. Lehman. Lake Victoria Plankton Ecology: Mixing Depth and Climate-Driven Control of Lake Condition; J.T. Lehman, et al. Caridina nilotica: Spatial Distribution and Egg Production in Lake Victoria, Uganda; G.B. Mbahinzireki, et al. Low-Oxygen Tolerance of the Atyid Prawn, Caridina nilotica, in Lake Victoria (East Africa): Implications for Refuge from Nile Perch Predation; D.K. Branstrator, L. Mwebaza-Ndawula. Secondary Production by the Lake Flay Chaoborus in Lake Victoria, East Africa; J.T. Lehman, et al. IDEAL Investigations of Rift Valley Lakes. Abrupt Climatic Changes Associated with the Arid Younger Dryas Interval in Africa; K.R.M. Beuning, et al. Nutrients and Plankton Biomass in the Rift Lake Sources of the White Nile: Lakes Albert and Edward; J.T. Lehman, et al. A Comparison of Isotopic Records in Abiogenic and Biogenic Calcite from Lake Turkana, Kenya; P. Ng'ang'a, et al. A Comparison between the Stable Isotopic Composition of Early Holocene and Late Pleistocene Carbonates from Lake Malawi, East Africa; R.D. Ricketts. Fluctuations of Rift Valley Lakes Malawi and Chilwa During Historical Times: A Synthesis of Geological, Archeological and Historical Information; S.E. Nicholson.

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