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

State of Saldanha Bay & Langebaan Lagoon 2011
Sediments
Enrichment factors calculated for both Small Bay and Big Bay indicated that the Cd levels
recorded in 2011 exceeded pre-development levels at all sites. The Yacht Club Basin was
approximately 28 times higher, while the multi-purpose quay site was 16 time higher (Table 5.4).
The results of 2011 indicate that the concentrations of Cd have increased at all sites within Small
Bay. Furthermore Cd was not detected in Big Bay or Langebaan Lagoon in 2010, however; in 2011
Cd was detected at all sites, with the exception of two in Langebaan Lagoon. This indicates a system
wide increase since 2010. Given the relatively pristine nature of some of the sites (southern lagoon)
and the great distance from storm water drains, it is likely that this increase is the result of natural
fluctuations. Indeed, Cd concentrations have been found to occur in naturally high concentrations in
the organic rich sediments of the near shore zone of the southern Benguela (including Saldanha Bay
area). It is important to note, however, that Cd levels did not increase consistently and in some
areas, notably the Yacht Club Basin, multi-purpose quay, Salamander Bay and Donkergat, the
increase is most likely attributable to anthropogenic activities in close proximity. Furthermore it
must be noted that neither Salamander Bay nor Donkergat were tested for trace metals prior to
2011 so it is unclear as to whether contamination occurred during 2009 or 2010.
5.4.2.2 Copper
Copper (Cu) is used as a biocide in antifouling products as it very effective for killing marine
organisms that attach themselves to the surfaces of boats and ships. Anti-fouling paints release Cu
into the sea and can make a significant contribution to Cu concentrations in the marine environment
(Clark 1986). Concentrations of Cu were detected at most sites in Saldanha Bay and Langebaan
Lagoon in 2011 (Table 5.3), with the exception of three sites in Big Bay and two in Langebaan
Lagoon. All sites with the exception of the Yacht Club Basin, the multi-purpose quay and Salamander
Bay had relatively low concentrations of Cu. The concentration of Cu at the Yacht Club Basin
exceeded the ERL.
The Yacht Club Basin had dramatically higher normalized Cu:Al ratio compared to other sites.
This area is subject to high boating activity. The input of Cu at this site may thus be related to the
use of antifouling paints, which characteristically have a high Cu content, and the sheltered nature of
this site. Other sites with high Cu:Al ratios included SB2, SB3, SB14 (multi-purpose quay) and S1
(Salamander Bay). The high ratios at SB14 are most likely attributable to a combination of the
depositional nature of the site and export and shipping activities, while that in Salamander Bay may
to be related to boating and, in all likelihood, the recent dredging activities. There is no apparent
reason for the elevated Cu:Al ratios found at SB2 and SB3.
Concentrations of Cu are 99 and 37 times greater than the historical average at sites SB1 and
SB14 respectively (Yacht Club Basin and Multi-purpose Quay). These sites are both depositional
zones for organic matter and are also associated with a high degree of boating/shipping activity. The
combination of boating activities as well at as the reduction of currents are most likely the primary
contributors to this long-term build up of Cu at these sites.
Figure 5.23 shows the temporal variation in Cu concentrations within Saldanha bay
sediments. As with all the other metals in Saldanha Bay sediments, Cu concentrations peaked in
1999 after the major 1997 dredging event. There was a subsequent decline in Cu concentrations
over the period 1999-2004 at the Mussel Farm, Channel end of the ore terminal, at the Multipurpose
quay, and within Big Bay. The concentrations of Cu in Big Bay and at the Mussel Farm have
remained low (