|
Climate changes and consequent increase in the minimum surface water temperatures in South African may favour the growth of various toxic bloom forming cyanobacterial species |
Chronic exposure to various toxic freshwater blooms found in water supply reservoirs may pose long-term hazards to human health. Climate changes that cause an increase in the minimum surface water temperatures in dams such as Midmar Dam in KwaZulu-Natal promote the growth of toxic blooms.
The toxic cyanobacteria are a diverse and widely distributed group of organisms that can contaminate natural and man-made bodies of water.
CSIR researcher Dr Paul Oberholster and colleague, Dr Anna-Marie Botha of the University of Pretoria, recently carried out a comprehensive study at Midmar dam.
"Predicting bloom events is an important goal of monitoring fresh water programmes," Oberholster says.
Published in the African Journal of Biotechnology, the aim of the research was to:
- Analyse a particular winter bloom in Midmar Dam with specific quantitative real-time methods to detect strains present and to determine their toxigenicity
- Investigate the taxonomic composition of phytoplankton at different sampling sites and the physical and chemical changes caused by waterfowl in the surface water of Midmar Dam.
Illnesses caused by cyanobacterial toxins in humans fall into three categories: gastroenteritis and related diseases, allergic and irritation reactions, and liver diseases. Similar bacteria have also been implicated as powerful tumour promoters and are suspected to be involved in the promotion of primary liver cancer in humans.
"Evaluation of the development of toxin concentrations in cyanobacterial populations during bloom events is thus important for the prediction of potential health hazards," says Oberholster. "Changing toxin concentrations in cyanobacterial blooms most probably reflect alterations in species and strain composition with various toxins and toxicities. Although prevailing water temperatures in South Africa are generally suitable for cyanobacterial growth during the greater part of the year, this is to our knowledge the first report of a cyanobacterial winter bloom in South Africa."
He adds, "Recent international studies have allowed us to augment our own investigation at a genetic level. It is general knowledge that, under certain environmental conditions, some species produce toxins that are released in water on the death of the cells. Studies in Europe and North America have demonstrated that 25 - 75% of blooms produced by toxic strains encountered in bodies of water such as Midmar Dam are toxic to humans."
Oberholster predicts an increase in mixed blooms of cyanobacteria and an increase in the incidence of poisoning by newly-introduced species in different climatic regions of South Africa in the near future, due to temperature increase caused by climate change.
Enquiries: Dr Paul Oberholster or CSIR Communications
|
