Abstract
Water is one of the most important resources in South Africa. The increased pressure on river systems in SA as a result of human activities and industrial development is evident from the systematic deterioration of the Olifants River (Mpumalanga). While the number of water users grows daily, the river is seen as a convenient disposal site. It is necessary to continually monitor the river to be aware of its status. Regular monitoring also supplements the existing data on water quality, biotic communities and possible points of pollution.
The study had the following aims:
Firstly to contribute to a larger project on the effect of pollutants on the physiology of fish populations in the Olifants River. This study concentrates on the bioaccumulation of certain metals (i.e. chromium, copper, iron, manganese, nickel, lead, strontium and zinc), in the gills, liver and muscle of Labeo congoro.
Standard methods were used to prepare the organs and tissues for metal analysis using atomic absorption spectrophotometry. The following conclusions were reached subsequent to statistical analysis of the results:
• The highest mean concentrations of all metals were recorded in the liver of Labeo congoro.
• The lowest mean metal concentrations were calculated in the muscle, except for chromium, the concentrations of which were the lowest in the gills.
• The highest mean concentration of each metal was recorded in organs / tissues of fish sampled at locality 2.
• None of the three localities can be singled out to indicate the lowest mean concentration of each metal.
Summary
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The second aim of this study was to determine the 96-hr LC50 (lethal concentration at which 50% of the test population dies) of nickel. Oreochromis mossambicus was used as test organisms for these laboratory studies. A flow through system was used to ensure that the organisms were exposed to the same concentration of nickel for 96 hours. Subsequent to the 96-hr LC50 determination, test organisms were subjected to sublethal exposure of nickel to determine the effects of the various concentrations of the haematology and blood coagulation processes of fish.
The following conclusions were drawn from the statistical data processing:
• The 96-hr LC50 of nickel for Oreochromis mossambicus is 50 μg.l-1.
• The exposure to sublethal concentrations of nickel did effect certain haematological variables
• No statistically significant differences in the blood coagulation variables at different sublethal concentrations of nickel were confirmed
The results of this study can be used to supplement the database on the water quality and general status of the Olifants River (Mpumalanga). The LC50 of nickel can be used as one of the variables in water quality studies.
Prof. Johan van Vuren