Page 38 - KBHA BULLETIN 2

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In addition to these and other examples of ecological succession, a major factor initiating

changes in the Bay has been overexploitation. This is clear in the case of the edible fishes but
this is also true of a number of rocky-shore invertebrates. In Gilchrist’s day, red bait was

abundant along the whole of the lower shore; now it is only to be found in relatively

inaccessible places. As far as sandy beaches are concerned, the most exploited animal has
been the white sand mussel Donax. Where they are not exploited, sand mussels attain

enormous densities until they are packed tight, squeezed up against one another; but in False

Bay those days are long gone and the population is very sparse.

False Bay’s sandy beaches have in fact possibly suffered more from human activity than have

its rocky shores. There are many reasons for this but in recent years a prime reason has been

the cleaning of the beaches by municipal workers. Well, I suppose holiday makers and
tourists are entitled to have clean beaches but the trouble is that removing all debris, including

marine algae, jellyfish and the like, deprives the intertidal community of its food. This has led

to a dramatic decline in many species. Added to this has been the levelling of dunes and the
hardening of surfaces in the provision of sub-economic housing and recreational facilities. As

a result of this, one of my favourite animals, an isopod named Tylos, is now extinct in False

Bay. There were plenty of them when I first studied the beaches between Muizenberg and
Strandfontein in the 1960s but not one has been seen for the last 25 years.

So what of pollution? I undertook a pollution survey of False Bay in 1988/89, summarising

all the literature and performing analyses of the water at various points. We found the water
from Cape Point north to Muizenberg corner to be virtually unpolluted by international

standards. Sure, there is some input and an occasional accident that leads to pollution but on

the whole the biota remains unaffected. Things begin to change along the stretch of shore
between Muizenberg and Strandfontein, there being quite considerable organic enrichment

from places such as Zandvlei and the outfall from the Strandfontein sewage works. This

organic enrichment leads to phytoplankton blooms in the surf - hence the patches of brown
water. These brown phytoplankton patches present no hazard at all either to human health or

to marine life, but they are unsightly and put many visitors off swimming.