Aquatic community response in a groundwater-fed desert lake to Holocene desiccation of the Sahara
Abstract
The finely laminated sediment record of a permanent, hypersaline, desert oasis lake in the Ounianga region of northeastern Chad presents a unique opportunity to document the hydrological evolution of this groundwater-fed aquatic ecosystem during mid- and late-Holocene desiccation of the Sahara. In this study we reconstruct long-term changes in zoobenthos and zooplankton communities of Lake Yoa as their early-Holocene freshwater habitat changed into the hypersaline conditions prevailing today. Chironomid production peaked during the fresh-to-saline transition period, then stabilized at about half
that of the earlier freshwater ecosystem. Quantitative salinity inferences based on fossil chironomid assemblages indicate that the fresh-to-saline transition occurred fairly abruptly between w4100 and 3400 cal yr BP, but that the ecosystem was buffered against shorter-term climate fluctuations due to continuous inflow of fossil groundwater. The mixture of tropical-African and southern Palaearctic chironomid faunas in the Lake Yoa fossil record required us to address several methodological issues concerning chironomid-based salinity reconstruction, and the applicability of a calibration dataset based on tropical East and West African lakes to this Sahara desert locality. The most coherent reconstruction
was obtained with an inference model that applies a weighted best-modern-analogue (WMAT) transfer function to the African calibration dataset expanded with six Sahara lakes.
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Bibliography
Eggermont H., Verschuren D., Fagot M., Rumes B., Bocxlaer B. V., Kröpelin S. (2008): Aquatic community response in a groundwater-fed desert lake to Holocene desiccation of the Sahara. In: Quaternary Science Reviews 27, Issues 25–26: 2411-2425
| author | Hilde Eggermont and Dirk Verschuren and Maureen Fagot and Bob Rumes and Bert Van Bocxlaer and Stefan Kröpelin |
|---|---|
| citation | Eggermont H., Verschuren D., Fagot M., Rumes B., Bocxlaer B. V., Kröpelin S. (2008): Aquatic community response in a groundwater-fed desert lake to Holocene desiccation of the Sahara. In: Quaternary Science Reviews 27, Issues 25–26: 2411-2425 |
| doi | 10.1016/j.quascirev.2008.08.028 |
| journal | Quaternary Science Reviews |
| key | 2008 |
| pages | 2411–2425 |
| type | article |
| volume | 27 |
| year | 2008 |