by Prof Anthony Turton

Gill Ledger in the Pecanwood wetland.

A citizen scientist, long involved in the Hartbeespoort Dam Integrated Biological Remediation Programme recently made a significant discovery of a microscopic filter feeder, with the grand name of Paradileptus conicus.
It is like a tiny basking shark spiralling through the water, consuming bacteria and algae along the way. The interesting aspect of this little fellow is that they are not common in South Africa. The very fact that they exist at all, is a tribute to the wisdom of the Pecanwood Remediation Plan, because that small wetland has created ecological conditions different enough from the dam, to support biological life that is less hostile to humans. More importantly, the water in which it is found is clear.
The discovery was made in a constructed wetland that has slightly different chemical properties to the rest of the dam. The reason for this difference is not fully understood, but is manifest as a slightly lower pH than the rest. The dam is highly alkaline, with a pH of 10 measured at the wall on occasion. The Pecanwood plan has created a smaller wetland adjacent to the 5th tee on the golf course, with a pH closer to 8, which is similar to seawater. It is in this small wetland that a few new species of microbiota are being recorded by Gill Ledger, a renowned citizen scientist.
This raises a glimmer of hope that it is possible to adapt to the presence of eutrophic water, by enabling small pockets of localized wetland habitat along the outer shoreline. These water bodies just have to be slightly different from the dam water to enable other species to exist there. This is how ecosystems work, where small niches, known as refugia, enable biodiversity to exist even in the harshest of conditions. It might also suggest that instead of eradicating hyacinth with Glyphosate, which merely enables the blue-green algae to flourish instead, it might be viable to reconsider the use of floating wetlands tethered in place to prevent their movement across the water. Those floating wetlands will also become refugia, and even if they do nothing else, they will compete for light and nutrients that the blue-green algae also need to survive.
Credit must be given to the Pecanwood HoA for their support of the Wetland Biological Remediation Plan as a cost-effective alternative to the use of Glyphosate. Even more credit to DACE, the provincial agency that is responsible for overseeing the Hartbeespoort Dam Integrated Biological Remediation Program. But this is also an excellent example of the role that citizen science plays in the management of our environment, especially where it is highly distressed.
We can expect other discoveries to emerge from Hartbeespoort Dam in the future, just as we can anticipate a change in the strategy underpinning the way we adapt to the long-term change caused by the uncontrolled inflow of sewage effluent into our rivers.