6 and 0 4 μg/g in mussels in Granger Bay and Green Point, respect

6 and 0.4 μg/g in mussels in Granger Bay and Green Point, respectively

(site 3), but they used different mussel species. The source of the zinc is thus uncertain and needs further investigation. Iron had the second highest concentration reported for the study period and the mean concentrations of Fe for all sites reported buy Staurosporine in this study (129.3 μg/g) is lower than that reported in other investigations where mussels were sampled (Shiber and Shatila, 1978 and Kavun et al., 2002). According to Giarratano et al. (2010), changes in marine Fe concentrations may be related to continental sources of Fe, as the major contributor to Fe is from rock weathering as a result of continental rainfall. Potential anthropogenic sources of Fe are from fertilizers, industry wastes, atmospheric deposition, solid waste disposal units and run-off from urban areas (Pergram and Görgens, 2001). The Fe tissue values recorded in the present study suggest that there are no major anthropogenic sources of Fe other than from urban GSK-3 phosphorylation run-off and the main source of Fe is postulated

to be as a result of rock weathering due to higher rainfall in autumn (Fig. 2d). According to Giarratano et al. (2010), Fe concentrations reported from their study came from natural sources, as human activities were not responsible for Fe input into the system. Cadmium concentrations (mean = 6.2 μg/g) were similar to that of Cu for the study period 1985–2008 along the west coast of the Cape Peninsula. However, the Cd levels recorded in this study are higher than the recommended SABS of 3.0 μg/g (South Africa, 1994). The values are higher than Cd values for mussels that were indicative of contamination (3.7 μg/g) set by Cantillo (1998). The levels for Cd were also higher than the 2.48 μg/g recorded by Henry et al. (1986) for Table Bay (sites 3–5). Cadmium occurs at high levels in the environment due to anthropogenic sources (Chiffoleau et al., 2001). Cadmium reactions cause various geochemical

processes such as the solubilization of Cd on freshwater particles when these reach sea water. As a result, Cd becomes available to molluscs living close to fresh water sources (Chiffoleau et al., 2001). This phenomenon could account for the higher levels of Cd at sites 2–5 as there are potential freshwater inputs such as river Carbachol mouths and stormwater pipes, although a study on metal concentrations from Diep River (freshwater input into Milnerton) showed low Cd concentrations in both water and sediment (Shuping, 2008). This cannot, however, explain the high values in site 1. The postulated reason for high Cd values at site 1 could be due to site 1 being a combination of two stations, where the mean Cd concentration in Noordhoek was 7.7 μg/g and in Olifantsbos was 6.0 μg/g. Noordhoek is a coastal area that could have substantial input of freshwater due to high levels of urbanisation.

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