CAIE IGCSE Biology 20.3.4 Eutrophication of Water
Practise sequencing eutrophication from nitrate enrichment and producer growth to decomposition, oxygen loss and organism death.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Exam points
- trace sewage or fertiliser runoff to increased nitrate ions and rapid producer growth
- link producer death to decomposition and increased aerobic respiration by decomposers
- explain that falling dissolved oxygen kills fish and other oxygen-dependent organisms
20.3.4—Process of eutrophication of water question 1
Researchers investigated the effect of adding cattle manure (cattle faeces) to fields where snap bean plants, Phaseolus vulgaris, were grown. Cattle manure contains some protein.
Snap bean plants are legumes which have root nodules that contain nitrogen-fixing bacteria.
Fig. 4.1 shows some root nodules.
Fig. 4.1
When large quantities of manure are put on fields it can lead to eutrophication of streams and rivers. This can lead to the death of fish.
Describe how eutrophication of streams and rivers can lead to the death of fish.
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