Paleoecological Analysis of Holocene Sediment Cores from the Southern Basin of Lake Tanganyika: Implications for Fish and Water Resources in One of Africa's Largest Lakes
Abstract
Extensive research has been conducted at Lake Tanganyika, Africa with the aim of understanding its vulnerability to both a warming climate and fishing pressure. However, much of this work has been restricted to its more accessible northern basin. This is insufficient to explain whole-lake dynamics of the world's longest lake. Whereas there is strong evidence from the northern basin that lake warming has played a critical role in causing decreasing fish abundance in Lake Tanganyika through increased stratification, it is unknown whether this is occurring lake-wide. Paleolimnological methods can be used to compare the trajectories of environmental change between these regions. This study seeks to provide insight into whether the 20th Century paleo-environmental changes observed in the northern basin (strengthening stratification and decreasing productivity caused by warming unprecedented in the late Holocene) are, in fact, a lake-wide phenomenon, and in the process help managers and policy makers to better manage the lake's fishery. Here, we present new paleoecological analyses from two sediment cores collected in 400 m and 680 m water depths from the southern basin of Lake Tanganyika. These were analyzed for fish bones, ostracodes and molluscs fossils every 2 cm and diatoms every 0.5 cm. Diatoms show upwelling events with high surface wave action at certain times, which favor the blooming and floating of relatively heavily silicified diatoms causing successions to vary in dominance between heavily-silicified and lightly-silicified diatoms. The presence of benthic invertebrates (ostracode and mollusc fossils) indicates more intense mixing and ventilation of the southern basin. Fish bone counts are highest during the major events of upwelling where heavily silicified diatoms and ostracodes peak. These features show dependence of lake productivity on convective mixing, which is counteracted by lake warming or decreased windiness through stratification.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC51G1150K
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 9305 Africa;
- GEOGRAPHIC LOCATION;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 1878 Water/energy interactions;
- HYDROLOGY