Tilapia now SA’s own bio-indicator of water pollution
Southern African water specialists can now use a local Tilapiine species – instead of alien fish species – to test whether water sources are polluted by compounds that can cause hormonal imbalances. Such chemicals can subtly mimic the female hormone oestrogen and alter the male hormone testosterone, whilst others disturb thyroid-hormone functioning.
Researcher Dr Marna Esterhuyse from the Botany and Zoology Department recommends the use of the hardy Mozambique tilapia – which is sensitive to water pollution – over that of the alien zebrafish which is currently often used as a bio-monitor.
“This work brings South Africa one step closer to its own fish model – similar to that of most developed countries – that can monitor chemicals in water sources that cause hormonal imbalances,” Dr Esterhuyse’s promoter, Prof Hannes van Wyk, believes. During such monitoring, scientists analyse the tissue, study the physiology and look at the changes in the genetic levels of fish species exposed to polluted water and chemicals.
“Aquatic animals are good bio-monitors because chemicals that cause endocrine imbalances are rapidly absorbed through the gills and stored in the body,” Dr Esterhuyse says.
Dr Esterhuyse’s toxicogenomic study focuses particularly on the interaction between pollutants and some of the genes specifically associated with the body’s endocrine systems. Due to Dr Esterhuyse’s genetic test model, fish exposed to a water sample can now be examined after only a few hours.
“Research on frogs, crocodiles and some fish species shows that endocrine disturbance caused by hormone mimics in polluted water results in, inter alia, deviations in the reproductive system and in the malfunctioning of the thyroid gland,” Dr Esterhuyse explains.
Pesticides (such as DDT), household products, by-products of paper- and plastic manufacturing industries and contraceptives all contribute to the number of endocrine disrupting compounds in our water effluent.
Dr Esterhuyse is now extending these studies with postdoctoral work on genes influenced by thyroid hormones.
Source: Science in Africa
Water pollution is a major problem in many of our dams and rivers. Polluted rivers have far-reaching downstream impacts; a small sewage/chemical spill can have a disproportionate effect on people and animals. An example is the highly contaminated Olifants River which gets polluted upstream in South Africa’s Highveld then continues on to cause animal die-offs hundreds of kilometres downstream in the Kruger National Park and Mozambique (crocodile die-offs are still occurring along this river system). Commercial and subsistence fishing is a source of food and income for many poor rural communities in the Lowveld and Mozambique. It is worrying that fish assimilate toxins so readily, especially the Mozambique Tilapia, also known locally as the Blue Kurper (Oreochromis mossambicus). This is one of the main species caught for food in the region. Much of the ‘accidental’ pollution of our waterways can easily be prevented but unfortunately there are still individuals and businesses who pollute our waters intentionally. As a home or business owner, one way of reducing pollution potential is to reuse grey water and keep it on your property (e.g. grey water irrigation for the garden). Stormwater runoff can also be reduced through rainwater harvesting and rainwater storage in water tanks. Storm water and gray water can potentially overload sewage works who then have no option but to direct the overflow to the nearest watercourse. Chlorinated water from pool backwashing is also very harmful to aquatic orgainisms. Water Rhapsody’s Poolside Tank recycles the backwash water and ensures that none enters the environment (and saves substantial quantities of water). See simulated product demos of all the Water Rhapsody systems.