State of the Bay Report 2010-Final - Anchor Environmental

13.2 Water Quality
13.2.1 Temperature, Salinity and Dissolved Oxygen
Anchor Environmental
From a water quality perspective, key physico-chemical changes that have resulted from
anthropogenic impacts on the Bay include modification in circulation patterns and wave exposure
gradients in the Bay, leading to a reduction in water movement and exchange between the Bay and
the adjacent marine environment.
There is currently no continuous monitoring of physico-chemical parameters (temperature,
salinity and dissolved oxygen) taking place in Saldanha Bay whereby the data are readily accessible
to the Saldanha Bay Water Quality Trust. It is strongly recommended that continuous (at least
hourly) monitoring of temperature and (if possible) oxygen be implemented at a minimum of three
locations in the Bay, including two stations in Small Bay (one specifically in the Yacht Club Basin), and
one station in Big Bay using similar methodology and station locations to that employed by the CSIR
(1999). It should be possible to download this data remotely and it should be analysed on a regular
basis. Furthermore, it would be beneficial to obtain such data from both surface and bottom waters
(i.e. 1 m and 10 m) to enable ongoing comparisons with historical data.
13.2.2 Chlorophyll a and Nutrients
There is currently no regular monitoring of chlorophyll a or nutrient concentrations
(specifically nitrogen and ammonia) taking place in Saldanha Bay. It is strongly recommended that
monthly monitoring of these parameters be implemented at a minimum of the same two stations
identified for temperature, salinity and oxygen monitoring. This may require manual samples to be
collected on a monthly basis and sent for laboratory analysis. Ongoing data analysis and
interpretation should form a part of such monitoring programs. These data would be invaluable in
calibrating existing hydrodynamic and biological production models that have been developed for
the Bay.
13.2.3 Currents and waves
Long term changes in the patterns of current flow and wave energy should be quantified
through a formal dedicated study to be conducted approximately every five years.
13.2.4 Trace metal concentrations in biota (MCM Mussel Watch Programme and
Mariculture Operators)
The concentrations of metals in the flesh of mussels are currently monitored by the Mussel
Watch Programme, which is conducted by the Department of Agriculture, Forestry, and Fisheries.
Data are available for the period between 1997-2001 and 2005-2007 but not since this time
apparently due to a backlog in processing of samples. The mussel samples collected from the shore
are analysed for the metals cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), iron (Fe) and manganese
(Mn), hydrocarbons and pesticides. No long term trends are evident in the data but it is clear that
concentrations of trace metals in the mussels from some sites in the Bay are way in excess of
guideline limits for foodstuffs for human consumption and are cause for considerable concern.
Data on trace metals concentrations in shellfish from the mariculture farms in the Bay were
also obtained from DAFF (courtesy of the farm operators). These results show that trace metal
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 260