Observations on the relation between phytoplankton diversity and environmental factors in the Vaal River at Balkfontein,South Africa |
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Authors: | A. J. H. Pieterse J. M. van Zyl |
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Affiliation: | (1) Department of Botany, University of the Orange Free State, P.O. Box 339, 9300 Bloemfontein, South Africa;(2) Department of Mathematical Statistics, University of the Orange Free State, P.O. Box 339, 9300 Bloemfontein, South Africa |
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Abstract: | The relationship between specific environmental factors as independent variables and temporal changes in phytoplankton community structure in the Vaal River (a turbid system) during 1984 was investigated by employing different diversity indices. Temporal changes in community structure reflected temporal changes in certain environmental factors. Phytoplankton diversity, measured with Shannon-Wie H' and Hurlbert PIE indices, was related firstly to discharge and discharge derived variables (such as SO4, Si, N and P loading) and secondly to turbidity derived variables (such as euphotic zone depth). Discharge appears to be of prime importance in affecting diversity. Observations were made that shed new light on conditions contributing to the development of an August peak (dominated by Stephanodiscus hantzschii fo. tenuis and Micractinium pusillum) in phytoplankton concentration. Increased environmental stress may reduce the number of sensitive species, thus reducing interspecific competition between tolerant species which could then exploit the — for them — more favourable conditions resulting in an increase in their numbers to peak concentrations. |
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Keywords: | Riverine environment phytoplankton community structure Shannon-Wie H′ and Hurlbert PIE indices |
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