Abstract
This paper discusses concentrations of 5 essential trace metals (chromium, copper, iron, manganese and zinc) in water, sediment and various fish (C. gariepinus) tissues. With the exception of high Zn concentrations in skin, the highest essential element metal concentrations were generally recorded in liver and gill arch tissues, followed by gill filaments and lastly skin and muscle. This general trend is in agreement with trends reported by other workers. Fe concentrations were found to be significantly higher at the Vaal Dam more often than at the Vaal Barrage. In comparison, Mn concentrations were higher at the Vaal River Barrage more often than at the Vaal Dam. No clear trends emerged with regard to differences between localities for the other metals, or between surveys/seasons for all essential trace metals examined. The likely reason for the lack of distinct trends is the amount of variability observed in tissue metal concentrations within localities and seasons in this study. Such variability is also reflected in current literature and accentuates the importance of both abiotic (e.g. physical water quality variables) and biotic (e.g. host physiological status, general biology and life history traits) factors influencing the concentrations and bioavailability of trace metals.
Highlights
Synopsis and scope of studyThere is increased public awareness regarding aquatic pollution, including metal pollution (Strydom et al, 2006)
Metal contamination of the environment may emanate from a variety of point sources of pollution, including mining and industrial activity (Kamau, 2002; Strydom et al, 2006; Van Aardt and Hough, 2007; Ayandiran et al, 2009), power generation, irrigation, sewage purification/treatment works (Coetzee et al, 2002), leachates from landfill sites (Moodley et al, 2007), motorboat exhausts (Van Aardt and Erdmann, 2004), leaching from domestic waste products associated with informal settlements (Jackson et al, 2007), other residential areas (Jackson et al, 2009), shooting ranges (Heier et al, 2009) and agricultural activities (Ali and Fishar, 2005)
Essential trace metals were recorded from C. gariepinus tissues
Summary
There is increased public awareness regarding aquatic pollution, including metal pollution (Strydom et al, 2006). Heavy metals can be defined as ‘electropositive elements having a density of greater than five’ (Roebuck, 1992). This definition invariably lumps together 40 metals of different properties and degrees of acute and chronic toxicity (Roebuck, 1992). Metal accumulation has been employed as an impact assessment tool with reference to fish health Apparent biomagnification of trace metals has been demonstrated to occur in some cestodes parasitising fish, making these organisms even more sensitive biological indicators of long-term metal pollution exposure (e.g. Woelfl et al, 2008; Retief et al, 2009; Oyoo-Okoth et al, 2010)
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