Biological observations on the crater lakes of Jebel Marra, Sudan
Article first published online: 20 AUG 2009
Journal of Zoology
Volume 189, Issue 4, pages 493–502, December 1979
How to Cite
Green, J., Moghraby, A. I. e. and Ali, O. M. M. (1979), Biological observations on the crater lakes of Jebel Marra, Sudan. Journal of Zoology, 189: 493–502. doi: 10.1111/j.1469-7998.1979.tb03976.x
- Issue published online: 20 AUG 2009
- Article first published online: 20 AUG 2009
- Accepted 10 April 1979
Two lakes lie in a caldera at the top of Jebel Marra. One is shallow and highly saline, with a dense bloom of planktonic blue-green algae and a zooplankton consisting entirely of rotifers. The other is over 100 metres deep, is less saline, with a sparse phytoplankton of diatoms, and the dominant zooplankter is Eucyclops gibsoni. The marginal fauna of the deep lake includes a number of widespread insects, but is unusual in that it includes an aquatic glowworm (Family Lampyridae).
In the shallow lake there is a superabundance of oxygen in the upper two metres, but no oxygen below six metres, except when strong winds mix the lake so that there is then about 40% saturation throughout the water column. In the deep lake it was found that after strong winds there was only about 12% saturation in the top 30 metres of water. The restricted fauna of these lakes appears to be a result of the combined effects of isolation, salinity and a variable oxygen regime.