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Q34 - Contrasting N:P Limitation Across European Coastal Waters

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Ecology

The use of fertilisers, and release of sewage, have altered the balance of nitrogen and phosphorus based nutrients in the environment. Additionally, nitrogen oxides from pollution dissolve in rain to form acids. Growing algae incorporates an average of 16 nitrogen atoms per phosphorus atom, and eutrophication occurs when algal decomposition depletes oxygen. In 1957, the River Thames was declared ‘biologically dead’, without oxygen, but is now among the world’s healthiest major rivers. Phosphorus availability (1), and nitrogen:phosphorus molar ratio (2) was measured across Northern Europe.

Figure for Q34: Contrasting N:P Limitation Across European Coastal Waters

Using the information and data, determine which of the statements are true or which are false.

A. The risk of eutrophication would be much lower if European farmers reduce phosphate, but not nitrogen, fertiliser use.
B. Nitrogen oxide pollution increases the risk of eutrophication around Great Britain.
C. Based on nutrient levels, British waters contain most of Europe's large, energetic fish species.
D. European rivers are more polluted with phosphate than nitrogen.
E. Nutrient levels allow algae to grow quicker along the East coast of Denmark, than the West.
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Question reproduced from IBO 2017, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions