Eutrophication

Eutrophication

1. Artifiical fertilisers containing nitrates, phosphates, and potassium are often added to soils to maximise the growth of crops. The addition of fertilisers can cause a body of water to become over-rich in nutrients, a process called eutrophication. One effect of eutrophication is to encourage the rapid growth of photosynthesising organisms especially algae. The dramatic, fast growth of algae is called an algal blloom. A bllom can smother large freshwater plants, reduce light intensity in the water, and produce toxins which kill fish. when the algal die, their decomposition by bacteria may lead to the complete deoxygeneration of the water, causing the death of aerobic organisms

2. Biological oxygen demand (BOD); as the density of microorganisms increases, their demand for oxygen also rises. This demand is called BOD. Oxygen depletion and eutrophication are not only caused by fertilisers. They may also be caused by any pollutant containing high concentrations of organic or inorganic nutrient, such as sewage,slurry or silage effluent whcih can leach off farmland and pollute water

3. Indicator species; indicator species can be used to monitor water quality and help detect incidents of water pollution by, e.e nitrate fertilisers. An indicator species is a species that needs a particular enviromental condition to survive. Whether the species is present, and it what numbers, provides information about the enviroment

4. Biological monitoring of water quality; the leaching of large volumes of fertilisers into fresh water habitts such as rivers has effects similar to the addition of sweage. There is an immediate impact on the enviroment at the point of entry and the pollutant reduces the quality of water for some way downstream. Changes in the abiotic enviroment are reflected by changes in the community of aquatic organisms