BIOACCUMULATION OF METALS IN SELECTED FISH SPECIES AND THE EFFECT OF PH ON ALUMINIUM TOXICITY IN A CICHLID OREOCHROMIS MOSSAMBICUS BY LIZET COETZEE THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE MASTER OF SCIENCES IN ZOOLOGY IN THE FACULTY OF NATURAL SCIENCES AT THE RAND AFRIKAANS UNIVERSITY SUPERVISOR: PROF H.H. DU PREEZ CO-SUPERVISOR: PROF J.H.J. VAN VUREN MAY 1996 - ACKNOWLEDGEMENTS - Special thanks to: My Lord for the wisdom, strength and insight He gave me: " By wisdom the Lord laid the earth's foundation; By understanding He set the heavens in place" "Wisdom is supreme, therefore get wisdom, though it cost all you have; get understanding" Proverbs 3:19; 4:7 My supervisor, Prof H.H. du Preez and co-supervisor, Prof J.H.J. van Vuren, for their support, motivation and guidance throughout the project Prof J.H. Swanepoel, the head of Department Zoology, for the use of the facilities and the opportunity to perform this study My parents for their patience, love and financial support during my studies My husband for his love, support and motivation; without him it wouldn't have been possible The Rand Afrikaans University, Water Research Board and the Foundation for Research Development for their financial support The Institute for Water Quality Studies, Department of Water Affairs and Forestry for the chemical analysis of the water samples Dirk Erlank Gabriel Motlhabane, Solomon Kwapa (Switch) and Solomon Tshabala (Sony) for their assistance with the experimental systems and my work in the aquarium Naas and Reinette Ferreira for the use of their computer and all their support Irma Naude for linguistically attending to my thesis Gail Nussey for all her support and advise -ABSTRACT- 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. ii 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. The selected water quality variables were mostly well within the guideline limits proposed for the protection of aquatic life, except for the phosphate concentrations, which were much higher than the permitted level of 1 mg/I for effluent water. The high phosphate concentrations in the water were due to effluent received from combined sewage purification works in the area of localities KOR1 and OR1, informal settlements situated alongside the river and agricultural runoff. With the exception of manganese, copper and zinc, the metal concentrations were higher than the recommended guideline limits. All the selected metals were, however, present in much higher concentrations in the sediments, especially iron and aluminium, with the highest concentrations found in the smallest particle sizes of the sediments. The high metal concentrations in the water and sediment indicated some degree of metal pollution, but due to the hardness of the water, these metals were not necessarily acutely toxic to the aquatic organisms. The general order of bioaccumulation of the selected metals was, in decreasing concentrations: Fe, Cr, Al, Ni, Pb, Zn, Mn and Cu in the water and: Al, Fe, Mn, Cu, Cr, Ni, Zn and Pb for the sediment, with exceptionally high concentrations of aluminium and iron. The different organs/tissues of the two species bioaccumulated different levels of the metals and it was clear which organs/tissues accumulated higher concentrations of a certain metal. The gills and liver tissues bioaccumulated the highest metal concentrations, with iii the highest concentrations of copper and iron found in the liver. These tissues should therefore be used for determining of the bioaccumulation of these metals in the fish. Although the lowest metal concentrations were found in the muscle and skin tissues, these tissues should always be included in general biomonitoring programmes, as it is consumed by humans and especially in this case, by the people from informal settlements located alongside the river, as well as anglers at locality OR1. High metal concentrations were found in the fish tissue, but concentrations in the muscle and skin tissue were still fit for human consumption. These concentrations should, however, always be monitored, as locality KOR1 receives effluent from combined sewage purification works located upstream from it, as well as raw sewage from informal settlements, different industries and urban and agricultural runoff. In addition to these sources, locality OR1 also receives effluent from mainly coal mines, situated in the catchment area. The results showed dependence of the bioaccumulation of most of the metals in the tissues/organs of both species, on the species and lengths of the fish, as well as the localities where the fish were collected. It is widely accepted that the water characteristics may influence the chemical form, availability and toxicity of various metals to aquatic organisms. The establishment of a general biomonitoring programme is therefore needed, where the hydrological and geomorphological characteristics, the chemical and physical water quality and the riparian vegetation are also considered, because these all affect the aquatic ecosystem. Identification of the lethal as well as sublethal effects of chemicals on living organisms is critical in evaluating and predicting the impacts of metal pollution. As previously stated, sublethal exposure of fish was performed to investigate the effects of aluminium and low pH, as these have caused fish kills in the catchment. Aluminium has different effects at different pH values and maximum toxicity occurs over the pH range 5.0 - 5.5. The fish were therefore exposed to pH 5.2, as well as combinations of pH 5.2 and iv different concentrations of aluminium. These concentrations were chosen with respect to concentrations found in the Olifants River and its tributaries during the present study. The results indicated sublethal effects (especially on the carbohydrate metabolism) of the fish at these concentrations and pH value. The pH values at the two localities used for description in this study were much higher, thus no serious aluminium toxicity to aquatic organisms is proposed. There are, however, problems with low pH at other localities of the upper catchment. Decreases in the pH values at localities KOR1 and OR1 due to acid mine drainage or low flow of the river, could cause serious problems, as the aluminium concentrations at these two localities in the sediments are very high and can lead to fish kills. Nutritionally and recreationally, fish constitute the most important segment of the aquatic ecosystem and therefore metal concentrations in fish are obviously of great concern. High concentrations of metals are toxic to the ecosystem as a hole and to humans in particular, since they are at the end of a variety of food chains by virtue of a varied diet. Further research is therefore needed as high concentrations of metals were found in the tissues and organs of the fish, as well as the sediment and water. It is suggested that the sources of pollution in the study area should be further investigated to fully understand the impact they have on the deteriorating environment. A detailed water quality