Abstract
M.Sc.
The upper catchment of the Olifants River, from its origin near Bethal, to its confluence
with the Wilge River, north of Witbank, as well as it tributaries, are being subjected to
increasing afforestation, mining, power generation, irrigation, domestic and industrial
activities. These activities have a profound effect on the water quality and the major
point sources of pollution in this area include mines, industries and very importantly,
combined sewage purification works, located alongside the river, which, in addition to
oxidizable material contains detergents, nutrients, and metals. It was therefore necessary
to determine the extent to which these activities affect the water quality of the system.
The impact of these activities was therefore addressed by a Water Research Commision
Project namely "Lethal and sublethal effects of metals on the physiology of fish" of
which the present study investigated effects at two localities, namely in the Olifants River
(locality OR1) before its confluence with the Klein Olifants River and a locality in the
Klein Olifants River (locality KOR1). Apart from the field study, toxicity tests were also
performed in a laboratory, in order to determine the effects of low pH and elevated
aluminium concentrations on the haematology, osmoregulation and carbohydrate
metabolism of the Mozambique Tilapia, Oreochromis mossambicus as the acidification
of soil systems may cause the transfer of aluminium into aqueous solutions, where it may
be present in different forms. During the field study, the chemical and physical
characteristics of the river water were evaluated, with special attention to the
concentrations of certain metals (manganese, copper, chromium, lead, nickel, zinc, iron
and aluminium) in the water and sediment, as well as in fish, which are known to
accumulate the elements supra and are therefore valuable as indicators of these
pollutants. The two fish species used for the investigations were the African sharptooth catfish,
Clarias gariepinus and the moggel, Labeo umbratus. Four tissue types were dissected,
namely the muscle, liver, skin and gill tissues. The metal concentrations in these
organs/tissues, as well as in the water and sediment, were determined in a laboratory with
an atomic absorption spectrophotometer. Statistical analyses were performed on the
results obtained from this study and the order and extent of bioaccumulation of these
metals in the water and sediment were determined, as well as in the fish organs/tissues.
Its dependence on the size, sex and species of the fish and the localities and seasons
were investigated.