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GCSE Biology · key term
Nutrient enrichment of water that can cause excessive algal growth and a fall in dissolved oxygen.
Used by AQA and Edexcel
Specification 4.7.3.2 · Paper 2
The enrichment of water by mineral ions, often from fertiliser, which can cause an algal bloom and a fall in dissolved oxygen.
Revise: Waste ManagementThe resulting oxygen shortage can kill aquatic animals. This sequence is called eutrophication.
Specification 4.13B, 9.9 · Paper 1, Paper 2
Revise: Agricultural SolutionsRain can wash excess minerals into rivers and lakes. This can cause eutrophication: nutrients encourage excessive algal growth, and the subsequent decay of algae can reduce dissolved oxygen, harming aquatic animals. Fertiliser use therefore needs to be judged by both its effect on crop yield and its possible effect on water ecosystems.
The enrichment of water with nutrients, leading to excessive plant or algal growth and often a loss of dissolved oxygen.
When explaining eutrophication, include the full sequence: fertiliser run-off → algal bloom → less light → aquatic plants die → decomposers respire → oxygen concentration falls → aquatic animals may die.
In eutrophication, explain that decomposers use dissolved oxygen while breaking down dead material; algae do not simply ‘use up all the oxygen’.
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