Bioaccumulation of chromium, manganese, nickel and lead in the tissues of the moggel, Labeo umbratus (Cyprinidae), from Witbank Dam, Mpumalanga

This paper focuses on the extent of Cr. Mn, Ni and Pb bioaccumulation in th e different tissues of a cyprinid fish, namely the moggel (Labeo umbratus) from Witbank Dam in the Upper Olifants River catchment. The dependence of b ioaccumulation on size, gender and seasons was specifically addressed. Bioa ccumulation of Cr. Mn, Ni and Pb varied between the gills, liver, muscle an d skin. The gills generally had the: highest metal concentrations, due to t heir intimate contact with the environment and their importance as an effec tor of ionic and osmotic regulation. The liver. in its role as a storage an d detoxification organ, can also accumulate high levels of metals. Muscles and skin accumulated much less metal concentrations. These two organs must be included in biomonitoring programmes because they are consumed by the ge neral public. Accumulation of the metals decreased with an increase in fish length. Therefore. the smaller the fish the higher the body load of metals due to various bioaccumulation processes. The accumulation of Cr, Mn and N i in the different tissues of male and female fish did not differ markedly. It is suggested that the male testes and female ovaries should also be com pared, in order to obtain further data on the differences of accumulation o f metals between males and females. The highest tissue concentrations of Cr , Mn, Ni and Pb with the exception of the muscle and skin tissues, were rec orded in the summer of 1995. The higher metal concentrations in the summer, compared to autumn and winter, can possibly be attributed to a varied wate r temperature.