Higher Eutrophication: When Too Much Nitrogen Is a Problem
Part of The Nitrogen Cycle · GCSE GCSE Biology revision
This higher tier covers Higher Eutrophication: When Too Much Nitrogen Is a Problem within The Nitrogen Cycle for GCSE Biology. The nitrogen cycle: nitrogen-fixing, nitrifying, denitrifying bacteria, ammonification, and the role of legumes It is section 11 of 14 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Topic position
Section 11 of 14
Practice
15 questions
Recall
15 flashcards
Higher Eutrophication: When Too Much Nitrogen Is a Problem
Farmers add nitrogen fertilisers to increase crop yields, but excess fertiliser can be washed by rain into rivers and lakes — a process called leaching. This leads to eutrophication:
- Excess nitrates enter rivers/lakes
- Algae and phytoplankton grow explosively (algal bloom) — blocking light
- Plants below the surface die (no light for photosynthesis)
- Decomposers (aerobic bacteria) multiply rapidly, breaking down dead plants
- Decomposers use up oxygen in the water (deoxygenation)
- Fish and other aquatic animals die from lack of oxygen
Eutrophication is the consequence of disrupting the nitrogen cycle — adding too much reactive nitrogen too quickly for the natural cycle to process. The same chain of reasoning appears in AQA 6-mark extended response questions.