By Peter Luhanga
Ongoing pollution of the once-pristine Milnerton Lagoon has reduced it to a "mere shadow of its former self" with the eradication of important prey species like prawns and blood worms, meaning that some varieties of birds and fish can no longer be found in the area.
Sewerage overflows into the Diep River, which flows into the Milnerton Lagoon, and illegal discharges into storm water systems in the Montague Gardens area have been fingered for the reduction in the lagoon's biodiversity.
But City of Cape Town environmental resource management department biodiversity co-ordinator Clifford Dorse said although many species of fish still occurred in the estuary these were generally more hardy species like Flathead Mullet and Southern Mullet.
City of Cape Town roads and stormwater department director Henry du Plessis said increased flows from the Potsdam Wastewater Treatment Works and channel modifications to manage floods, "has resulted in a reduction in biodiversity in the system over the past few decades".
High levels of pollution are also hazardous for humans.
Tests of the Diep River at the Otto du Plessis Drive bridge above the lagoon show faecal coli levels of more than 1 000 000 per 100ml and E.coli levels of more than 700 000 present in every 100ml of water, according to City of Cape Town figures on October 30. This fails to comply with Department of Water Affairs and Forestry regulations of less than 1 000 faecal coli per every 100ml.
High faecal coliform counts increased the risk of gastro-intestinal illnesses and skin conditions even for non-contact activities such as sailing and canoeing, Du Plessis said.
Woodbridge Island body corporate trustee for environment and waterfront Richard Rundle described pollution of the Diep River as a "tragedy".
Environmentalist Andy Birkinshaw said although upgrading of the Potsdam Waste Water Treatment Works had been going on for three years, effluent flow was still "sub-standard".
He said the lagoon was one of a few estuaries in the Western Cape, but was no longer a recreation area.
Department of Environmental Affairs and Tourism spokesperson Mava Scott said the City of Cape Town had entered into an agreement with CapeNature to commission an Estuaries Management Plan.