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The tiny water flea, Daphnia, is crucial to the restoration of good quality water in Loskopdam.
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CSIR researchers are investigating whether indigenous sedge can be used
as a purification system by planting them in buffer zones in the 'Upper
Olifants River catchment. In Europe a form of sedge is commonly used in
artificially constructed purification beds.
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The solution for the water quality problems plaguing Loskopdam can only be found in the upper catchment of the Olifants River and the return of tiny water zooplankton like water fleas (Daphnia).
At the release of the interim research report on the health of the Olifants River, CSIR senior researcher Dr Paul Oberholster said it is well-known that the dam is polluted by a toxic mix of excessive nutrients from raw or partially treated sewage, agricultural fertiliser and run-off from cleared land, as well as acid mine drainage and industrial effluents.
What researchers are only starting to understand, though, is how polluted waters like Loskopdam's can affect the insect population - which means there are hardly any smaller insects - like the water flea - to clean the dam from algae.
"Polluted waters, infested with hardy cyanobacterial species, are not a good habitat for the smaller species of insects like Daphnia or Bosminia - better known as water fleas. Their mouth parts are too small to tackle the large blue-green algae cells, so they die out and the cyanobacteria are allowed to grow undisturbed," Oberholster explains.
"Less zooplankton also implies less food for the fish - which is why we are only finding algae in the fishes' stomachs instead of zooplankton. The problem here is that the algae accumulates heavy metals from the polluted waters, and then ends up in the fish and higher up in the food chain."
Many zooplankton avoid grazing on cyanobacteria species such as Microcystis aeruginosa as it produces microcystin - a toxic substance that can cause animal and human death when eaten. In 2008 Oberholster and his team found varying levels of mycrocystin concentrations in the dam - from 8.2 ug/l in February 2008 to a peak of 46.7 ug/l in March of the same year.
Oberholster is adamant that Loskopdam's water quality will only improve by preventing and controlling pollutants entering the system in the upper catchment. Apart from working closely with the Olifants River Forum to address those problems, the interim report also explores the way forward, with several possible scenarios and solutions to be researched further.
One such solution is the creation of buffer zones to protect the upper tributaries of the river where it flows close to heavy industry, agricultural areas or waste water treatment works.
CSIR botanist Klaudia Schachtschneider is working with indigenous sedge from the various sampling sites and testing for its ability to accumulate heavy metals in its roots and leaves. In Europe a form of sedge is commonly used in artificially constructed purification beds. Sedge usually grows in wetlands and close to water bodies, where their densely tangled roots contribute to erosion control and water purification.
The research team, consisting of over 30 researchers from the CSIR, the universities of Stellenbosch and Pretoria, as well as the Department of Water Affairs and the Mpumalanga Tourism and Parks Agency, will continue sampling and monitoring water quality and other ecological health indicators at over fifteen sites in the catchment of the Upper Olifants River.
Apart from monitoring water quality, researchers will use geographical information systems to better understand land-use patterns around the rivers in the upper catchment, in order to link specific pollutants to specific land uses or impacts.
The research team also plans to do a health risk assessment of the various sampling sites and pinpointing sources of contamination. In this regard they work closely with local communities dependent on drinking water from the Olifants and its tributaries.
For more information, visit the Olifants River Forum's website.
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