The impact of harbour and associated activities on the water quality of the Durban Bay and their effects on indwelling ecosystems.

Abstract

Coastal systems like lagoons and estuaries are faced with severe human developmental endeavours. In South Africa, more than 30% of the population lives along the 3000 kilometer coastline. The Durban bay is no exception especially with the existing Durban harbour taking up the natural expanse of the bay. The bay is burdened with a diversity of anthropogenic endeavours, from port operations to industrial activities, to storm water drainage outlets, through to various recreational ventures. These activities have over the years caused a reduction of the bay‘s mangrove forest, reduced the population of some biota and caused extinction of some indigenous species. Five areas were selected based on the specific activities and infrastructure that occurred there. Samples of water from these pre-selected sites were collected routinely and analysed for their water quality status. The overall water quality within the bay compared with the DWAF water quality guidelines for South Africa was identified as below stipulated standards. The dissolved oxygen contents as well as nutrients in the form of nitrogen content in its assorted forms are some of the most affected water quality indicators. The majority of the sub standard water quality levels, indicators which are critical to the proper functioning, growth and reproduction of biota within the ecosystems of the bay obtained could be linked directly or indirectly to the activities within the area of sampling. The resultant chemical and physical conditions in water quality created as a result of the ongoing activities within the bay are not suitable for proper feeding, growth and reproduction of ecosystems. This has caused many species within the bay to migrate or adapt to the adverse conditions and such situations are likely to worsen if stringent measures are not taken in the near future. It appears that the some species are exhibiting some degree of resilience and are at the moment surviving the relatively harsh conditions within the bay. The long term effect of the ever expanding anthropogenic disturbances on the ecosystems are unpredictable and it is therefore imperative that more stringent environmental management plans, programs and policies, legally binding, are formulated to serve as a check on all who benefit from the bay‘s resources.