Two locals went hiking at the back side of Island Lake in the Wilderness National Park. They were shocked when they encountered green waters that they described as “looking like paint”. They’d seen it slightly green before but nothing like this.
I immediately thought that it was similar to the coastal red tide. Basically, an excess of nitrogen and phosphorous, combined with hotter water, creating an algal bloom that’s very green in colour.
The question is whether it’s an all natural process of coincidences or promoted by pollution (sewerage or fertilisers).
I contacted Nandi Mgwadlamba at SANPARK’s, asking her if she was aware of it and if there had been a water sample with results.
She emailed that they were aware and that Rangers had first suspected an invasive, aquatic plant called salvinia molesta. But that was soon ruled out as salvinia grows in slow-moving, fresh waters as opposed to the salty water of Island Lake. They believe it to be an algal bloom but it is too soon for them to be conclusive.
Regards water quality, although no recent test was done, she encouraging said that:
“Work is underway to understand water quality in the system include ongoing work by SANParks scientists and recently the development of a water quality index by Dr. David Le Maitre of the Council for Scientific & Industrial Research (CSIR).
The index is meant to predict the impact of different land use activities on the quality of streams and rivers. It’s being piloted in the Wilderness lakes catchment.
The goal is to inform citizens and other land-use groups regarding the use of their living and working landscapes to protect water in the catchment area. The tool examines how different land uses ultimately affect the quality of water flowing to the Wilderness Lakes area, the sea and surrounds. Once finalized, this tool should be able to highlight impact hots pots in the catchment. Such impacts can potentially be countered through maintaining healthy riparian buffers.
The project will consider the national land cover – whether an area is a natural ecosystem, degraded or mined area, and will list different vegetation structures. This will ultimately provide an indication of which sections of a river are affected by which land use.
The recent round of the study focused on the Duiwe River and Langvlei Spruit where agricultural practice is the dominant land use.”
Algal blooms, whether natural or man made, are toxic so please don’t swim in it.
Hopefully a water test will tell us more.