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eutrophication — English
The human-induced chemical and biological changes in the water of a fresh-water body such as a river, lake or dam. Eutrophic water is heavily polluted and contains high concentrations of various chemical compounds, and especially phosphate and nitrate compounds. These chemical substances are plant nutrients that enhance the growth of plants that grow in the water itself (for instance waterlilies and algae), as well as the riparian vegetation (for example reeds and bamboo) that grow on the floodplain and banks of fresh-water bodies. Most of these plants are strong growing pioneer plants that flourish on the additional nutrients in the nutrient enriched eutrophic water. The vigorous growth of the plants lessens the oxygen content of the water. Consequently fish, crabs, waterbirds, and many other forms of aquatic life would struggle to survive or will simply die and disappear from the ecosystem (see “ecology”, “ecosystems” and “wetlands”). Hence, an entire ecosystem could be vastly changed or even destroyed by eutrophication. Recreation activities such as boating, waterskiing and angling are hardly possible in water bodies that are totally covered by water plants. This may have a dramatic negative effect on the tourist potential of an entire region. The origins of the pollutants include fertilizers used for crop cultivation that are washed into the water by runoff, industrial waste water which is pumped into some water body or other, and inadequate sewerage systems which result in the deliberate or inadvertent deposition of raw human waste (excreta) in some nearby water body. Eutrophication is one of the most difficult and expensive environmental problems to solve. A rather spectacular example of eutrophication is found in the Hartebees Poort Dam in Gauteng. The water in the dam contains very high concentrations of nitrates and phosphates. To make matters worse the surface of the dam is usually completely covered by non-indigenous hyacinths which have accidently washed into the dam many years ago and flourish because of the nutrient-rich, polluted water of the dam. Despite numerous ongoing attempts to eradicate the hyacinths, by means of an array of methods, no successful way to permanently solve the problem has yet been found.
