Vol.:(0123456789) 1 3 Bull Environ Contam Toxicol DOI 10.1007/s00128-017-2100-z A Multivariate Analysis of Metal Concentrations in Two Fish Species of the Nyl River System, Limpopo Province, South Africa R. Musa 1  · R. Gerber 1  · R. Greenfield 1   Received: 28 July 2016 / Accepted: 27 April 2017 © Springer Science+Business Media New York 2017 dissolved in the aqueous medium, suspended as particulate matter due to turbulence or in suspension with ligands by means of adsorption (Vanloon and Duffy 2005). Regard- less of being essential or not, all metals in a system with concentrations exceeding naturally occurring quantities produce toxic effects on the living organisms in the system (Greenfield et al. 2012). Increased pollution of the natural environment is ulti- mately tied to population increases. Pollution sources stem from rural and urban development which comprise of industrial, agricultural and domestic effluents (Laws 1993). Management of these fragile ecosystems is therefore essen- tial to ensure the sustainability of these freshwater systems to support life (Crafford and Avenant-Oldewage 2010). The potential of wetlands to mitigate the negative impact of floods, store water and most importantly control pollut- ants via water purification, proves the need to ensure its existence and management (Vlok et al. 2006). The impacts of mining, industrial and agricultural activities prove detri- mental to wetlands (Greenfield et al. 2012). Contaminants from mining and industrial activities are usually from dif- fuse sources, increasing metal loads in waterbodies and the organisms that inhabit them. The need for clean freshwater for human consumption as well as other human activities makes the quantitative and qualitative assessment of pollu- tion of wetlands an important task (DWAF 1996). According to Moiseenko et al. (2008), fish are good indicators of pollution in a system, as they appear to be more susceptible to toxicants than most invertebrates. Since metals are not readily sequestered out of the fish’s tissues, they do not just offer information of the present quality of the water but symbolize the history of the system (Auth- man et al. 2015). The feeding habits of Clarias gariepinus (Burchell 1822) and Oreochromis mossambicus (Peters 1852) makes them ideal representatives to assess the Abstract Increased toxicity due to high metal concentra- tions may hinder the ecological integrity of aquatic eco- systems in sustaining life. The non-biodegradable nature of metals may result in bioaccumulation in aquatic organ- isms. Due to ecological and social aspects it is imperative for monitoring schemes to identify possible impacts to the systems integrity. This paper discusses accumulation patterns of seven metals (Al, Cr, Cu, Fe, Mn, Sr and Zn) in tissues of two fish species, namely Clarias gariepinus and Oreochromis mossambicus at two selected sites, the first located upstream of Modimolle (NRS1), and the sec- ond located downstream of the town (NRS2). Gills, liver, muscle and skin tissues were analysed for metal concentra- tions using standard microwave digestion and inductively coupled plasma mass spectrometry techniques. Statistical results indicated higher concentrations of metals at NRS2 in comparison to NRS1, indicating that Modimolle plays a potential role in introducing metals into the aquatic system. Keywords Bioaccumulation · Clarias gariepinus · Discriminant function analysis · Metals · Oreochromis mossambicus · Ramsar Metals occur naturally in all systems (Gbem et al. 2000; Coetzee et al. 2002; Eneji et al. 2011). The natural con- centrations found depend on the geo-chemical processes of the environment. In aquatic systems, metals can be found * R. Greenfield rgreenfield@uj.ac.za 1 Department of Zoology, University of Johannesburg (Auckland Park Kingsway Campus), PO Box 524, Auckland Park 2006, South Africa