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

State of Saldanha Bay & Langebaan Lagoon 2011
Recommendations
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
concentrations away from the shore are much lower than those in nearshore water and mostly meet
guidelines for foodstuffs for human consumption.
In the light of the fact that large qualities of shellfish are harvested and consumed by
recreational and subsistence fishers from the shore of the Bay, it is imperative that this Mussel
Watch Program is continued and possibly extended to cover other species as well (e.g. fish).
12.2.5 Microbiological monitoring (Faecal coliform)
Water samples are currently analysed fortnightly for faecal coliform and E. coli concentrations from
20 stations in Saldanha Bay and Langebaan Lagoon. Faecal coliform counts in Small Bay regularly
exceed water quality guidelines for recreational and mariculture use. Despite guideline values being
exceeded in Small Bay, there has been a general improvement in water quality over the last decade
but these gains seems to be dropping off again now. Water quality (bacterial counts) for Big Bay fall
mostly below guideline limits, however there has been a notable decline in water quality within Big
Bay over time and this is of some concern. There appear to be limited bacterial contamination
within Langebaan Lagoon, but levels are clearly increasing with time, and unmitigated erosion of
Langebaan beach may increase the risk of sewage pollution via broken or leaking sewage holding
tanks. It is imperative that management steps are taken to improve water quality within Small Bay,
especially in the vicinity of the Bok River mouth (sewage outlet). The upgrading of sewage
treatment and storm water facilities needs to match the rate of development in order to prevent
any further degradation of water quality within the Bay. The current level of monitoring should
continue as such with regular analysis and interpretation of data taking place.
The older DWAF water quality guidelines for recreational use have recently been revised
following an international review of guidelines for coastal waters, which highlighted several
shortcomings in those developed by South Africa. The revised guidelines (RSADEA 2011) are based
on counts of intestinal Enterococci and E. coli, and require that both types of bacteria be
enumerated at least every two weeks. It is highly recommended that enumeration of Enterococci be
included in the Saldanha water sampling programme in place of faecal coliforms as several studies
have shown faecal coliforms and E.coli to be relatively poor indicators of health risks in marine
waters. These organisms are also less resilient than Enterococci (and other pathogenic bacteria) so if
analysis is focussed on coliforms, risk can be underestimated due to mortality occurring in the time
taken between collection and analysis. Guidelines state that samples should be collected 15-30 cm
below the surface, on the seaward side of a recently broken wave. Samples to be tested for E. coli
counts should be analysed within 6-8 hours of collection, and those to be tested for intestinal
Enterococci, within 24 hours. Analyses should be completed by an accredited laboratory, preferably
one with ISO 17025 accreditation.
12.3 Sediments
12.3.1 Particle size, Particulate Organic Carbon and Trace metals
Sediment monitoring in the Bay has revealed that key heavy metal contaminants (Cd, Pb, Cu, and Ni)
are increasing at a number of sites in the Bay, particularly in Small Bay, to the extent that they are
almost certainly impacting on benthic fauna and possibly other faunal groups in the Bay. These
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