A case study from the Buffelspoort Valley Conservancy
By Noel Pope
Chairman: Buffelspoort Valley Conservancy
If you happen to see an elderly gent or lady sitting alongside a stream in the Buffelspoort Valley Conservancy ostensibly scrubbing some pebbles from the river with a toothbrush, there’s no need to be concerned about their sanity.
What they are doing is taking a sample of the Diatom population in the water.
And why would they be doing that?
One of the best ways of monitoring the quality of water in a stream is to measure the number and variety of Diatom organisms established in colonies on pebbles in running water.
Over the years scientists in South Africa and elsewhere in the world, notably Europe, have developed accurate assessment methods which relate Diatom counts to water quality.
The assessment requires an extremely high level of competence in carrying out the laboratory work and also demands sophisticated equipment, mainly high powered microscopes, all of which is provided by the NW University at Potchefstroom.
However, the sampling process can be successfully carried out by non scientific operators after very little guidance and instruction. Furthermore, the samples do not have to be so carefully handled because the silica cell structures of the Diatoms are almost indestructible – hence elderly gents and ladies wading in streams with their toothbrushes!
“Community participation and awareness are becoming increasingly important in the monitoring of South Africa’s water resources. When one considers the vast area, and the diverse climate and geology of many parts of the country, it is very difficult for water managers, governmental agencies and interested members of the public to obtain an accurate reflection of the status of all water bodies,” says Dr Jonathon Taylor. The study was initiated by the Conservancy and adopted by Dr Jonathan Taylor, scientist at the North West University.
A paper was published in the “African Journal of Aquatic Science” 2009, 34(2) pp 173 to 182 and describes the method of sampling and the results obtained over three years.
A Diatom count reflects not just the conditions in the water at the time and place of sampling, but also the average state of the river water flowing over the pebbles for a long period before the time of sampling.
The method makes it easy to involve local communities in monitoring water quality which would be impossible for the scientists working on their own.
The Buffelspoort Valley Conservancy has taken samples for 3 years in succession.
These show that the water in the river catchment of the Buffelspoort Dam is of a very high quality. The dam water is, however, mildly alkaline which could impact on the aquatic community structure but as yet not at a level that will affect the potability of the water. Vigilance is necessary with regard to what is entering the Dam from the surrounding developments.
“While no scientist can possibly cover a territory as large and diverse as South Africa, with the help of communities, this clearly becomes possible,” says Dr Taylor.
The diatoms are a commonly occurring group of algae belonging to the Bacillariophyceae. The characteristic that best distinguishes them from other algae is the siliceous nature of their cell wall. This robust cell wall makes them resistant to damage during sample collection and preparation. As microorganisms, they have few habitat restrictions and are easily dispersed, readily colonising most aquatic habitats and extending into moist aerial habitats and even into dry terrestrial habitats
The method is useful for evaluating water quality and providing understandable information to communities, especially concerning the degradation of a water body, which is not necessarily reflected by chemical data. Diatom species distribution is largely limited by water quality”