A 1.2 million year record of ecosystem evolution from Lake Malawi, Africa’s most biodiverse lake

Andy Cohen Lake

Long records of Quaternary ecological and climatic change are critical to understanding the range of potential responses of ecosystems to environmental forcing. In Africa, where complex and ancient tropical ecosystems are important parts of the landscape such records are still relatively rare. In this talk I will present an integrated lake and watershed paleoecological analysis from drill core records obtained by the Lake Malawi Drilling Project, documenting extraordinary fluctuations in climate, hydrology and ecosystem response for the southern tropics of Africa. High resolution lacustrine and terrestrial paleoecology and sedimentology data sets from these Early Pleistocene-Holocene drill cores provide the most complete record of this duration currently available from Africa.

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Time series analyses of these records demonstrate the important role that insolation, and especially ~400ka eccentricity modulated precessional cyles Malawi ecosystems. We observe shifts between more arid conditions (shallow alkaline and well mixed lake, with discontinuous desert vegetation) and more humid environments (deep, stratified, freshwater lake with dense forest). These broadly synchronous changes in lake paleoecology, lake sedimentology, and watershed vegetation demonstrate the major role of climate in regulating this system. Transitions between these lake/watershed state extremes is often very abrupt, suggesting that the combined lake/watershed repeatedly passed through hydroclimate thresholds, with important implications for the evolution of the lake’s endemic biodiversity and ecosystem. Lake Malawi also appears to have undergone a major state change after 800-700ka with an adjustement in base level of hundreds of meters that appears to reflect a change in outlet position driven by tectonics. All of these cyclic and non-cyclic changes provide an environmental template against which we can much better understand the adaptive radiation of cichlid fishes which has occurred in the lake, one of the most biodiverse lakes on earth.

 

Prof. Andrew Cohen (University of Arizona)

My research area is paleolimnology, the interpretation of lake history from sedimentary and paleontological records. Most of my work to date has involved studies of depositional environments, paleoecology, and climate history of the African Rift Lakes and the arid climate lakes of the western US. I use paleoecological and sedimentological records as primary tools in the interpretation of lake deposits, from both outcrops and sediment cores.

Event Information:

Date, Time:04/07/2016, 14:00 h – 15:00 h

Location: Room S12, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne

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