UA Department of Geosciences

Research | Paleolimnology

In the East African Rift Valley

We have an extensive research and research training program on tropical lakes and their history focused on the East African rift system, specifically Lakes Tanganyika and Malawi. At Tanganyika, we are engaged in studies about Miocene-Holocene climate change (Lezzar et al., 1996; Cohen et al., 1997 a and b, and Alin et al., 2003), and studies of anthropogenic impacts on tropical lake ecosystems, specifically the record of deforestation and accelerated erosion in the watersheds of tropical lakes as inferred from core records (Cohen et al., 1993; Cohen, 1994; Alin et al, 1999; Wells, et al., 1999; Cohen, 2000; Alin et al., 2002). Strong evidence exists linking recent climate change related to regional and global warming with tropical lake warming and changes in lake circulation, which are having an impact on Lake Tanganyika's ecosystem and fisheries (O'Reilly et al., 2003).

Our group has participated in numerous coring campaigns around Lake Tanganyika to better elucidate it's history. Other projects have concerned subjects as diverse as the history of rift lake tectonic development (Cohen et al., 1993; Soreghan and Cohen, 1993, 1996; Lezzar et al., 1996, 2002) and the evolution and co-evolution of endemic animals in the lake (Michel et al., 1991, Michel 1994; West and Cohen, 1994, 1996, Park et al., 2000, 2001, 2002) Much of this work has occurred through the auspices of the Nyanza Project, an NSF/UN funded interdisciplinary research training program in tropical lakes, based at Lake Tanganyika. The University of Arizona paleolimnology group is also heavily involved in the planned Lake Malawi Drilling Project. This project, a collaboration between scientists at Syracuse University, the University of Minnesota, the University of Rhode Island and the University of Arizona, will collect a series of several hundred meter long cores from Lake Malawi in late 2004, in the process obtaining a high resolution record of tropical climate change for East Africa during much of the Quaternary (Cohen et al., 2000).

References

Alin, S., Cohen, A., Bills, R., Gashagaza, M.M., Michel, E., Tiercelin, J.J., Martens, K., Coveliers, P., Mboko, S., West, K., Soreghan, M., Kimbadi, S. and Ntakimazi, G. 1999. "Effects of landscape disturbance on animal communities in Lake Tanganyika, East Africa." Conservation Biology 13:1017-1033.

Alin, S.R., O’Reilly, C.M., Cohen, A.s., Dettman, D.L., Palacios-Fest, M.R., and McKee, B.A., 2002. "Effects of land use change on aquatic biodiversity: A view from the paleorecord at Lake Tanganyika, East Africa." Geology 30:1143-1146.

Alin, S.R., and Cohen, A.S., 2003. "Little Ice Age drought history in East Africa: Lake level reconstruction using paleoecological ostracod assemblages." Palaeogeog., Palaeoclim., Palaeoecol 199:31-49.

Cohen, A., Bills, R., Cocquyt, C. and Caljon, A. 1993. "The Impact of Sediment Pollution on Biodiversity in Lake Tanganyika." Conservation Biology 7:667-677.

Cohen, A.S., Soreghan, M. and Scholz, C. 1993. "Estimating the Age of Ancient Lake Basins: An Example from L. Tanganyika." Geology 21:511-514.

Cohen, A. 1994. "Extinction in Ancient Lakes: Biodiversity Crises and Conservation 40 Years after J.L. Brooks." In Martens, K., Gooderis, B., and Coulter, G. (eds.) Speciation in Ancient Lakes. Arch. Hydrobiol 44:453-481.

Cohen, A. 1995."Paleoecological Approaches to the Conservation Biology of Benthos in Ancient Lakes: A Case Study from Lake Tanganyika." Jour. North Amer. Benthological Soc. 14:654-668.

Cohen, A., Kaufman, L. and Ogutu-Ohwayo, R. 1996. Anthropogenic threats, impacts and conservation strategies in the African Great Lakes — A review, in The Limnology, Climatology and Paleoclimatology of the East African Lakes (T. Johnson and E. Odada, eds): Gordon & Breach Publ.:Newark, N.J., p. 575-624.

Cohen, A.S., Talbot, M.R., Awramik, S.M., Dettman, D.L. and Abell, P. 1997. "Lake level and paleoenvironmental history of Lake Tanganyika, Africa as inferred from Late Holocene and modern stromatolites." Geol. Soc. Amer. Bull. 109:444-460.

Cohen, A.S., Lezzar, K.E., Tiercelin, J.J. and Soreghan, M.R. 1997. "New palaeogeographic and lake level reconstructions of Lake Tanganyika: Implications for tectonic, climatic and biologic evolution in a rift lake." Basin Research 9:107-132.

Cohen, A.S., 2000. "Linking spatial and temporal change in the diversity structure of ancient lakes: Implications for both theoretical ecology and conservation biology." In Rossiter, A. and Kawanabe, H. (eds.) The Biology of Ancient Lakes, Academic Press:San Diego, p. 521-538.

Cohen, A.S., Scholz, C.A., and Johnson, T.C., 2000. "The International Decade of East African Lakes (IDEAL) drilling initiative for the African great lakes." Jour. Paleolimnology 24:231-235.

Lezzar, K., Tiercelin, J.J., DeBatist, M., Cohen, A.S., Bandora, P., Van Rensberger, P., Le Turdu, C., Mifundu, W. and Klerkx, J. 1996. "New seismic stratigraphy and Late Tertiary history of the North Tanganyika Basin, East African Rift System, deduced from multichannel and high resolution reflection seismic data and piston core evidence." Basin Research 8:1-28.

Lezzar, K.E., Tiercelin, J.J., Le Turdu, C., Cohen, A.S., Reynolds, D.J., Le Gall, B., and Scholz, C. 2002. "Control of normal fault interaction on the distribution of major Neogene sedimentary depocenters, Lake Tanganyika, East African Rift." Amer. Assoc. Petrol. Geol. Bull. 86:1027-1059.

Michel, A.E., Cohen, A.S., West, K., Johnston, M. and Kat, P. 1991. "Large African Lakes as Natural Laboratories for Evolution: Examples from the Endemic Gastropod Fauna of Lake Tanganyika." S.I.L. Mitteilungen Series 23:109-116.

O’Reilly, C.M., Alin, S.R., Plisnier, P.D., Cohen, A.S., and McKee, B.A., 2003. "Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa." Nature 424:766-768.

Park, L.E., Cohen, A.S., and Martens, K., 2000. "Ecology and speciation of the ostracod clade, (Gomphocythere) in Lake Tanganyika, East Africa." Verh. Internat. Verein. Limnol. 27:2665-2669.

Park, L.E., Cohen, A.S., and Martens, K., 2001. "Ecology and speciation of the ostracode clade Gomphocythere in Lake Tanganyika, East Africa." Proc. XXVII Soc. Intl. Limnol. Congress, Dublin, 27:1-5.

Park, L.E., Martens, K., and Cohen, A.S., 2002. "Phylogenetic Relationships of Gomphocythere (Crustacea: Ostracoda) in Lake Tanganyika, East Africa." Journal of Crustacean Biology 22:15-27

Soreghan, M.J. and Cohen, A.S. 1993. "The Effects of Basin Asymmetry on Sand Composition: Examples from Lake Tanganyika, Africa." In Johnson, M. and Basu, A. (eds.) Geol. Soc. Amer. Spec. Publ. 284:285-302.

Soreghan, M. and Cohen, A. 1996. "Textural and compositional variability across littoral segments of Lake Tanganyika: The effect of asymmetric basin structure on sedimentation in large rift lakes. American Association of Petroleum Geologists Bulletin" 80:382-409.

Wells, T., Cohen, A.S., Park, L.E., Dettman, D. and McKee, B. 1999. "Ostracode stratigraphy and paleoecology from surficial sediments of Lake Tanganyika, Africa." Jour Paleolimnology 22:259-276.

West, K. and Cohen, A. 1994. "Predator-Prey Coevolution as a Model for the Unusual Morphologies of the Crabs and Gastropods of Lake Tanganyika." In Martens, K. et al. (eds.) Speciation in Ancient Lakes. Arch. Hydrobiol. 44:267-283.

West, K. and Cohen, A.S. 1996. "Shell microstructure of gastropods from Lake Tanganyika, Africa. Adaptation, convergent evolution and escalation." Evolution 50:672-681