The influence of the diel climatic cycle on the depth-time distribution of phytoplankton and photosynthesis in a shallow equatorial lake (Lake Baringo,Kenya) |
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Authors: | Graeme Patterson Kiplagat K Wilson |
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Institution: | (1) Department of Botany, Kenyatta University, P.O. Box 43844, Nairobi, Kenya;(2) Present address: Natural Resources Institute, Chatham Maritime, ME4 4TB Chatham, Kent, UK |
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Abstract: | Lake Baringo is a shallow equatorial lake. This paper reports a diel study of the depth-time distribution of phytoplankton
and photosynthesis at one location in Lake Baringo on 10 March 1989. The water column shows a pattern of diurnal stratification
probably accentuated by the high turbidity of the water and therefore rapid attenuation of solar energy. This stratified pattern
breaks down at night due to atmospheric cooling and the regular onset of winds in the early evening. The phytoplankton is
dominated byMicrocystis aeruginosa with some associated epiphytes. It concentrates in the narrow euphotic zone during the diurnal period of stratification due
to buoyancy of theMicrocystis; evening breakdown of the thermocline results in the phytoplankton being mixed throughout the water column. A series of measurements
of photosynthesis throughout the diurnal period gives an areal rate of 3.8 g O2 m−2 d−1. The relationship between this value and the level of fish exploitation in Lake Baringo is discussed. The diel cycle in Lake
Baringo is interpreted as dominating over any seasonal limnological cycle in the lake. |
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Keywords: | diel cycles phytoplankton photosynthesis tropical lakes fish yields |
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