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Biological observations on the crater lakes of Jebel Marra, Sudan
Author(s) -
Green J.,
Moghraby A. I. el,
Ali O. M. M.
Publication year - 1979
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1979.tb03976.x
Subject(s) - biology , water column , plankton , crater lake , salinity , fauna , phytoplankton , brackish water , zooplankton , algae , ecology , oceanography , paleontology , geology , volcano , nutrient
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.