State of the Bay Report 2011-Final.pdf - Anchor Environmental

State of Saldanha Bay & Langebaan Lagoon 2011
Water quality
The mussel samples are analysed for the metals cadmium (Cd), copper (Cu), lead (Pb), zinc
(Zn), iron (Fe) and manganese (Mn), hydrocarbons and pesticides. A new automated method for
sample preparation, including microwave digestion, has recently been adopted (Watling 1981; G.
Kiviet pers. comm.). Data from the mussel watch programme are represented in Figure 4.9 where
the maximum legal limits prescribed for each contaminant in shellfish for human consumption in
South Africa, as stipulated by the Regulation R.500 (2004) published under the Foodstuffs, Cosmetics
and Disinfectants Act, 1972 (Act 54 of 1972), are indicated in red text. Where guidelines have not
been specified in national legislation those adopted by other countries have been used (Table 4.8).
Data supplied by the Mussel Watch Programme (Figure 4.10) show that concentrations of
Lead in mussels at the monitored sites are consistently above guideline limits for foodstuffs over the
period 1997–2007, while concentrations of Cadmium frequently exceed these limits, and those for
Zinc do so occasionally. Concentrations of Copper are, however, well below specified levels (Table
4.8). No clear trends over time are evident for any of the trace metals, although recent data (post
2007) are lacking.
Concentrations of Lead in mussels from Saldanha Bay tend to be consistently high at the
TNPA site (at the base of the iron ore terminal on the Small Bay side, values generally greater than
60 ppm), occasionally spiking to very high level at this site (715 ppm in Oct 2001), but tend to be
lower at the other sites (mostly below 10 ppm), although they occasionally spike to high levels at
these sites as well (e.g. 250 ppm at the mussel rafts site at the base of the Marcus Island causeway).
Compared with the guideline limit of 0.5 ppm these levels are extremely high and are very
concerning. These high levels of Lead in are almost certainly linked to the export of Lead ore from
the multipurpose quay, which is situated in close proximity to the TNPA site. Levels of Cadmium in
mussels from Saldanha Bay are less variable than Lead and appear to be of a similar magnitude at all
sites (mostly between 1-10 ppm) but occasionally exceed this level. Relative to guideline levels this
is very high and is also cause for concern for anyone who may be consuming these mussels. Levels
of Zinc are mostly within the range of 50-200 ppm but occasionally have been observed to spike to
levels as high as 400 ppm or more which is way in excess of the guideline limit of 150 ppm listed by
the Canadian authorities (Table 4.8).
Rights holders engaged in bivalve culture (mussels and oysters) in South Africa are also
required to report on concentrations in harvested organisms on an annual basis. Data were
obtained for three trace metal indicators (Cadmium, Lead and Mercury) for three farms (Blue Bay
Aquafarm, West Coast Aquaculture, West Coast Oyster Growers and Striker Fishing) in Saldanha Bay
covering the period 1993-2010 (Figure 4.10). Data from these farms suggest that the situation in the
deeper parts of the Bay where the farms are located is less of a problem than in the case with the
nearshore coastal water where the Mussel Watch programme samples are collected.
Concentrations of Lead were consistently above guideline levels in the period prior to 2000, albeit
nowhere near as high as for the nearshore mussel samples (never more than 3 ppm), but since this
time have been mostly within guideline limits (i.e. less than 0.5 ppm). Concentrations of Mercury in
the mussel flesh from the farms has also mostly been within guideline limits (i.e. less than 0.5 ppm),
apart from one or two spikes above this level (maximum concentration recorded = 1.7 ppm in 1994).
Concentrations of Cadmium have always been within guideline limits (