An ecological study of the macro-invertebrate fauna of the Eerste River, Western Cape Province, South Africa

King, Jacqueline Mary

An ecological study of the macro-invertebrate fauna of the Eerste River, Western Cape Province, South Africa

Doctoral Thesis

1982

Abstract

The Eerste River is situated in the south-western Cape Province, South Africa. Its upper reaches have a stony substratum, and can be divided into three physical/biotic zones: The Mountain Stream, Upper River and Lower River zones. Investigations of the abundance, biomass, species diversity and species composition of the benthic macro-invertebrates in the three zones were carried out in 1975/76. Spatial and temporal changes in these factors can be correlated with changes in the physico-chemical quality of the water. Abundance and biomass generally increased downstream, but were low below a dam construction-site, because of the blanketing effects of silt on the substratum. Seasonal changes in abundance and biomass differed in the three zones, but always included a peak in spring. The highest values of both were in the Lower River in summer, reflecting the build-up of organic pollutants there during times of low flow. Diversity of the Ephemeroptera, which was felt to be representative of a change in.diversity of the fauna as a whole, generally decreased downstream, with a major drop at the town of Stellenbosch, and another at a sewage-farm outfall. A misleading increase in diversity occurred, however, in the silt-laden waters below the dam site,. due to the fleeting occurrence of individuals of several different species. Composition of the fauna was typical of local rivers with mountain sources. Figures for abundance, biomass and calorific values of species are given in appendices

Keywords

Zoology

Reference:

Collections

PhD / Doctoral

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