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SERA Water Focus Area Team member, Dr Paul Oberholster (CSIR) |
Researchers from the SERA Water Focus Area Team have recently produced an article published in the African Journal of Biotechnology showing a strong positive correlation between the increase in surface water temperature and the increased occurrence of toxic blooms in South Africa's inland water resources even in the winter months.
The evidence provided in the article by Team members, Dr Paul Oberholster - CSIR; Dr Jan Myburgh - UP, and Prof Anna-Maria Botha from Stellenbosch University supports the researchers' predictions of an increase in blooms of toxic blue-green algae and subsequent poisoning incidences in South Africa: This, if current trends in climate change continue.
In addition to warmer surface waters being conducive to the formation of these blooms, when combined with heavily polluted waters, this could also lead to circumstances ideal for mixed and even more lethal toxic blooms. Toxins produced by biological organisms can affect both the liver and nerve system.
According to Oberholster - a limnologist, cyanobacterial blooms have become an increasing problem in South Africa, posing a significant threat to the health of animals and humans. "The massive proliferation of these organisms in rivers and lakes is largely due to progressive eutrophication. However, a warming trend in the southern hemisphere, with minimum temperatures increasing three times faster than maximum temperatures, is likely the cause of the increasing occurrence of toxic cyanobacterial bloom forming species. Previously these were hampered by low water temperatures," he explains.
"The most alarming characteristic of cyanobacteria is the ability of many species to produce a range of extremely potent low-molecular-weight cyanotoxins. These cyanotoxins are grouped according to the target physiological systems, organs, tissues or cells. Cyanotoxins that affect the nervous system are called neurotoxins, while hepatotoxins break down liver cell integrity. Cytotoxins, also known as cellular toxins, cause cell death or damage genetic material, while lipopoly-saccharide (LPS) endotoxins can cause skin, eye and respiratory irritation," they explain in the article.
Concerns over the health risks to humans by these cyanotoxins have prompted the World Health Organization (WHO) to adopt a provisional guideline value for microsytin-LR in drinking water. In the case of South Africa there are guidelines for cyanotoxins in domestic water (only for microcystins) but values are not specified for drinking water guidelines or national drinking water standards.
In South Africa, most drinking water comes from surface waters, where cyanobacteria have been recorded in many, if not most instances. Due to climatic conditions and excessive nutrient loads from agriculture and discharge of treated sewage, Microcystis and Anabaena cyanobacterial genera often dominate the phytoplankton of reservoirs and rivers in the central and northern regions of South Africa.
Oberholster, Myburgh and Botha plead for early warning systems and risk management strategies to be put in place in South Africa.
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