Abstract
M.Sc.
The Hartbeespoort Dam is located in the North-West Province, downstream of
the confluence of the Crocodile River and the Magalies River. The dam was
originally built for agricultural purposes and the surrounding area has many
canals for irrigation. The use of pesticides for agricultural practices within the
area which are transported by the canals, are of great concern. It is well known
that residues of persistent pesticides (especially those of organochlorine) and
insecticides are found in terrestrial and aquatic environments as well as in the
organisms occupying these niches. Such xenobiotics are highly lipid soluble and
lengthy exposure to them results in their high accumulation in non-target
organisms, all contributing to adverse effects on the ecosystem.
The upper Olifants River catchment comprises the drainage areas of the Olifants
River, Klein Olifants River and Wilge River, with tributaries down to the Loskop
Dam. Over the past few years, the Olifants River has been systematically
impaired because of an increase in agricultural and mining activities, industrial
development and urbanisation. Recent fish kills in the Loskop Dam has lead to
many controversies about the water quality in the Olifants River.
The aim of this study was to determine through the use of biomarker responses if
it would be possible to identify whether sub-lethal pesticide exposure occurs in
fish populations in the Crocodile- and Olifants River systems. Both active
biomonitoring (ABM) and passive biomonitoring (PBM) were carried out at
selected sites in the Crocodile River system. The ABM technique involved the
transplantation of bioindicator organisms, in this case fish, and exposing them for
a period of four weeks. The ABM and PBM exposures were carried out during
different pesticide spraying regimes, which also coincided with high (summer)
and low (winter) flow conditions. Following the exposure period, the organisms
were removed and assessed for biological responses (biomarkers). General
biomarker responses used in pesticide exposure i.e. acetylcholinesterase
(AChE), malondialdehyde (MDA), catalase activity (CAT), protein carbonyls (PC),
cellular energy allocation (CEA) and condition factor (CF) were determined. The
same suite of biomarkers used in the Crocodile River system was used to
determine responses in resident fish species in the Olifants River system.