The influence of a marina canal system on the ecology of the Kromme estuary, St Francis Bay

Abstract

The influence of the marina canals on the lower reaches and mouth area of the Kromme estuary was investigated. Surveys were conducted during 1978 and 1979 in the marina system as well as in the main estuary in the vicinity of the marina. Analyses and comparisons of the biotic communities in the marina and in the main estuary showed a very similar composition, but differences in density were observed for several of the species. The plankton and nekton samples in the estuary and in the marina showed the same seasonal trends in abundance. The abiotic characteristics of the marina canals were also investigated and special attention was given to water circulation in the system during a tidal cycle. These observations showed that water circulation throughout the entire system was good, indicating efficient flushing and tidal turnover. Temperature, salinity and dissolved O₂ values indicated well-mixed and saturated waters. It is concluded that the marina has, in effect, increased the habitat area for plankton, benthic macro-invertebrate fauna and fish and that it does not have an adverse effect on the ecology of the Kromme estuary.