Aspects of marine fouling in western Cape waters
Two independent investigations into aspects of marine fouling were conducted in Simonsbay and Table Bay during 1979 to 1981. The development of macrofouling communities on six test materials was examined at 10m and 20m depths in Simonsbay for periods ranging from one month to one year. Community development was similar on inert non-reactive materials, aluminium, stainless steel, fibre glass and polyvinylchloride, but was reduced on non-wettable silicon rubber and corrodible mild steel. Macrofouling was characterized by seasonal succession with minimum colonization rates during winter, when adverse weather and low temperature conditions prevailed. The nature of fouling differed with depth. At 10m depth, mussel and barnacle-dominated communities developed rapidly, while at 20m depth, ascidian and barnacle-dominated communities developed more slowly. The role of primary film formation in the colonization of substrata by invertebrates was investigated in short-term studies conducted in Simonsbay and Table Bay. Surface-bound antibiotics, streptomycin and penicillin, were used to inhibit bacterial proliferation, while a herbicide, diuron, was employed to prevent diatom growth. The colonization by invertebrates was monitored on these surfaces and compared to surfaces where primary film development was normal, or where it was advanced by pre-culturing in laboratory seawater. It was found that invertebrates attached soon after panel exposure and that differences in the degree of primary film development were of little consequence to their settlement. The apparent discrepancy of these observations with previous findings is discussed, with special reference to the location of test sites in relation to mature communities.
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