D4.2.8—Eutrophication
Eutrophication occurs when nitrate or phosphate enrichment drives algal blooms, decomposition, increased oxygen demand, hypoxia, and major aquatic biodiversity loss.
- Syllabus
- First assessment 2025
- Objective
- D4.2.8
- Level
- SL
Exam analysis
Chance of appearing1%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1A
Typical marks1
Common command terms
- Explain
- Discuss
Scoring notes
- Common mistake
- Saying algae directly use up all oxygen, instead of linking oxygen loss mainly to aerobic decomposition of dead organic matter.
Recent exam appearances
May 2025Paper1A ["SL"] · TZ130[ 1 ]D4.2.8—Eutrophication
Practice this objective
Coverage 2025–2025 · Updated 16 Jul 2026
Concept essentials
- Nitrate and phosphate enrichment commonly starts eutrophication in aquatic ecosystems.
- Algal blooms increase organic matter that aerobic decomposers break down.
- Higher biochemical oxygen demand lowers dissolved oxygen and can kill aquatic organisms.