Acid mine drainage has had devastating consequences for the river system and the high diversity of fish that lived in the river. It has affected the last remaining refuge area of the upper Olifants River, established through the National Water Act and its Resource Quality Objectives as vital for the sustainability of the whole upper Olifants River catchment.
Acid mine drainage or AMD is usually associate with coal mining and includes the spillage of toxic, polluted water from mining areas, which carries metals, radionuclides (atoms that emit radiation) and salts in concentrations that radically changes river environments and is hazardous to all aquatic life.
In the eastern parts of Gauteng and western Mpumalanga around our coal fields, AMD is one of the most important threats to our rivers including our iconic indicator fishes such as our yellowfish (Labeobarbus spp), which was once abundant, but now uncommon in our rivers, along with all of the rest of our aquatic wildlife.
Dr O’Brien the abundance and diversity of fish species has declined drastically over the last two decades across southern Africa. He said we are in danger of unsustainable development that could affect all of our futures.
A 2011 study titled: An assessment of the influence of multiple stressors on the Vaal River, South Africa, by Dr O'Brien and other authors, which was conducted at the Vaal River, assessed the risk of multiple stressors to fish populations, and found that the regions that were predicted to be at greatest risk to exposure of multiple stressors, did indeed display disturbance in fish community structures.
“Our rivers are vulnerable ecosystems that are out of sight and out of mind,” says Dr O’Brien.
Dr O'Obrien and his team of researchers found that there are multiple stressors that contribute to the decline of the yellowfish in our rivers.
In the early 2010’s the team of researchers identified the threats to fish health due to rapid changes in available oxygen and increased oxidative stress associated with exposure to metals such as copper and nickel as well as organic pollutants. It is evident that a significant change in the fish community structures exists within the study area and that this change is in the form of an increase in dominance of the hardy species such as the sharptooth catfish and alien species such as Carp in Vaal Barrage are for example.
“When I was training in the late 1990s we used to do yellowfish population and health work around the Barrage area, just south of Joburg. We used to spend days and days processing fish because there were so many, the abundance was incredible," he adds.
“Now you don’t find many indigenous fishes there, and importantly no largemouth yellowfish any more. And now in the last 15 to 20 years we have seen another massive change.”
The multiple stressors which Dr O’Brien refers to include: the constant flow of inadequately treated sewage into the river, effluent released from local industries and mines and of course AMD water spills.
Dr O’Brien further added that due to altered flows and habitat modifications the important fish’s habitat had been destroyed. And that: “Our fish are particularly vulnerable because they deal with flow, water quality, habitat changes and other stressors such as alien species, over fishing and disease which all affects our water resources.”
Their research pointed out that potential drivers of this change in community structure include changes in the water quality of the Vaal River below the confluence between the Vaal and Blesbokspruit/Klip rivers and or due to habitat alterations.
The consequences of these drivers have been the complete removal of indigenous species that are sensitive to modified water quality and those species that have a high preference for specialised riverine habitats or substrates.
The abundance and diversity of fish species has declined drastically over the last two decades across southern Africa
Inadequate protection
The study further warned that the inclusion of higher tier assessment endpoints to elucidate the effects of multiple stressors in aquatic ecosystems was important.
Today, more that 10 years after the research on the Vaal River, reality hits hard. The quality of the Vaal, Crocodile West and Olifants Rivers has been seriously modified resulting in massive loss of the biodiversity of our ecosystems and their processes which we all depend on.
We are using our water resources excessively and not controlling over development and or the abuse of our rivers through water abstraction, release of effluents, habitat alterations and release of alien species and diseases that affect our precious water resources.
“It’s not that we don’t have the legislation to sustainably develop and conserve our water resources, we do. We are not adequately implementing them and or do not really have the desire to protect our resources or understand how inadequate protection will affect all of us in the long run! This will catch up with all of us one day, and we will all pay the price."
@ Story Lisa Thabethe. Pictures Supplied.