Saldanha water quality has a worrying down trend.June 26, 2009 by: admin
Despite some positive signs regarding improved water quality readings in Saldanha Bay and the Langebaan lagoon – an internationally protected Ramsar site – the overall picture is of a natural environment being incrementally degraded, say scientists.
The ‘State of the Bay 2008: Saldanha Bay and Langebaan Lagoon’ report by Anchor Environmental Consultants, released on Thursday last week, revealed detailed analysis of discharges from human activity; water quality; sediments; benthic macrofauna; intertidal invertebrates; fish and birds.
A number of worrying trends are contained in the report, presented by Barry Clark from the University of Cape Town (UCT) Zoology Department.
One of these was the overall downward trend in the number and diversity of benthic macrofauna (species larger than 1.0mm in size living in sediment) in all three bays studied: small bay; big bay; and Langebaan lagoon.
The poorest results in the entire spectrum of tests were obtained from small bay – which showed the most ecological degradation over all, with parts of it being a “dead zone”.
There were some improvements in the health of benthic macrofauna in big bay compared to previous years, one notable success being the return of the sea pen Virgularia schultzei to the area.
Langebaan lagoon has seen little change over recent years, but, as with the other areas, comparisons to data from 1975 show a marked decrease in benthic macrofauna diversity and abundance.
There was also a worrying decline in the resident wading bird population in Langebaan lagoon, an area which is seen as the most important wetland for these birds on the west coast of Southern Africa, and is ranked as the fourth most important estuary for waterbirds.
Although there did not seem to be any real long term changes to fish communities in the bay, there is “some evidence to suggest that tolerant species are becoming more abundant while more sensitive species are declining in abundance”.
While the bay supported what was probably the last healthy population of white stumpnose, a major drawcard for both commercial and recreational fishermen, Clark noted that about 40% of the adult white stumpnose population was being caught, a situation which was “not sustainable”.
He said the health of the current population was likely due to the Langebaan lagoon serving as a protected nursery, and degradation of that ecosystem would have severe negative consequences.
And the health of the white stumpnose population could not be taken for granted.
“There is a trend toward severe exploitation of this stock, and the balance may soon be tipped.”
Thus fishing in the bay required proper, enforced controls.
The report noted that dredging activities carried out by Transnet had marked negative effects on the health of the bay as it stirred up fine particulate matter, unearthing the toxic metals which clung to it.
To Transnet’s credit, they kept harbour dredging activities to a minimum, but the planned phase 2 expansion of the iron ore terminal would require extensive dredging activities, further compromising the quality of the bay’s ecosystem.
Increased shipping as a result of the expansion would also involve increased amounts of polluting ballast water, taken in at highly polluted Eastern ports and containing pollutants and alien species which were then released into the bay, as well as increased risk of spills and accidents. – West Cape News
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