State of the Bay Report 2010-Final - Anchor Environmental

Anchor Environmental
In South Africa to date, an estimated total of 85 marine species are recorded as introduced
mostly through shipping activities or mariculture and at least 62 of these are thought to occur in
Saldanha Bay-Langebaan Lagoon (Mead et al. in press). Three of the species recorded in Saldanha
Bay are considered invasive: the Mediterranean mussel Mytilus galloprovincialis, the European
green crab Carcinus maenas (Griffiths et al. 1992; Robinson et al. 2005) and the recently detected
barnacle Balanus glandula (Laird and Griffiths 2008). Most of the introduced species are found in
sheltered areas such as harbours and are believed to have been introduced through shipping
activities, mostly ballast water. Because ballast water is normally loaded in sheltered harbours, the
species that are transported also originate from these habitats and thus have a difficult time
adapting to South Africa’s exposed coast. This might, in part, explain the low number of introduced
species that have become invasive along the coast (Griffiths et al. 2008). Most introduced species in
South Africa occur along the west and south coasts and very few have been recorded north of Port
Elizabeth. This corresponds with the predominant trade routes being between South Africa and the
cooler temperate regions of Europe, from where most of the marine introductions in South Africa
originate (Awad et al. 2003). (Section 12 of this report deals with alien invasive species in Saldanha
Bay in more detail.)
Other potentially negative effects of ballast water discharges are contaminants that may be
transported with the water. Carter (1996) reports on concentrations of trace metals such as
cadmium, copper, zinc and lead amongst others that have been detected in ballast water and ballast
tank sediments from ships deballasting in Saldanha Bay. Of particular concern are the high
concentrations of copper and zinc that in many instances exceeded the South African Water Quality
Criteria (DWAF 1995a) (Table 4.4). These discharges are almost certainly contributing to trace metal
loading in the water column (as indicated by their concentration in filter-feeding organisms in the
Bay - see § 5.6 for more on this) and in sediments in the Bay (see §127 for more on this issue).
Ballast water carried by ships visiting the Port of Saldanha is released in two stages - a first
release is made upon entering Saldanha Bay (i.e. Big Bay) and the second once the ship is berthed
and loading (Awad et al. 2003). As a result as much as 50% of the ballast water is released in the
vicinity of the iron ore quay on either the Small Bay side or Big Bay side of the quay depending on
what side the ship is berthed (Figure 4.1).
Table 4.4. Mean trace metal concentrations in ballast water (mg/l) and ballast tank sediments from ships
deballasting in Saldanha Bay (Source: Carter 1996) and SA Water Quality Guideline limits
(DWAF 1995a).
Water Sediment SA WQ Guideline limit
Cd 0.005 0.040 0.004
Cu 0.005 0.057 0.005
Zn 0.130 0.800 0.025
Pb 0.015 0.003 0.012
Cr 0.025 0.056 0.008
Ni 0.010 0.160 0.025
The total number of ships entering the Port of Saldanha has nearly doubled in the last two decades
and currently averages some 400 ships per year (Figure 4.15). As a result, the volume of ballast
water discharged to the Bay has also increased by more than double since 2004, with close to 20
million tons of ballast water being discharged each year (Figure 4.16). Iron ore tankers are
responsible for most of the observed increase in vessel traffic and are the ones responsible for
discharging the greatest volume of ballast water into the Bay.
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 62