Eutrophication Peter Fergie What is the problem? • Eutrophication is a process by which an excess of nitrates can kill of populations of water-based organisms. • This is due to the build up in nitrates increasing the population sizes of some plants in the water through increased fertility. • When these plants die, there is an excess of organic dead matter. • This dead matter is then used by bacteria in aerobic respiration, allowing the bacteria to absorb more oxygen from the water. How does that affect other organisms? • With more oxygen being absorbed by the bacteria, there is less available for larger organisms which don’t have the necessary adaptations to cope with lower oxygen levels. • These organisms, often fish, can then no longer respire aerobically and will therefore die. • This affects the whole cycle exponentially, as there is now more dead matter, and therefore more bacteria respiring aerobically, causing the O2 levels to decrease further, therefore causing more and more fish to die. Why is this happening? • This problem occurs when farmers use artificial chemical fertilizers on their land. • These fertilizers contain large amounts of Potassium, Phosphorus and Nitrogen. • It’s the nitrogen which causes all the problems, in the form of nitrates. • An excess of these will be washed out from the fields by the rain in a process called “run-off”, where the nitrates then accumulate in nearby rivers and ponds. • This then links back to the original slide where the water plant population increases. How can the problem be overcome? • The magnitude of the problem can be decreased by a number of factors. • These include not overly fertilizing fields, using an organic fertilizer, and not releasing raw sewage into rivers and lakes. • A reduction in fertilizer usage would leave the land with less excess nitrates going to waste and causing eutrophication.
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