IB Biology SL D4.3.7 Coral Reef Threats Questions

Explain how warming disrupts coral–zooxanthellae mutualism and acidification suppresses calcification, threatening reef biodiversity.

Exam points

Explain how warming disrupts coral–zooxanthellae mutualism, reducing photosynthesis and causing bleaching, starvation or coral death.
Explain how ocean acidification lowers carbonate availability or calcification, damaging coral skeletons and reef habitat.
Link bleaching and acidification to coral-reef biodiversity decline and ecosystem consequences.

[Maximum number: 2]

High-temperature tolerance experiments were performed on Pocillopora damicornis, a coral in the tropical eastern Pacific, in the Gulf of Panama. The scattergraph shows the zooxanthellae densities at three temperature treatments over a 10-week period.

Figure for Question IB Biology SL D4.3.7 Coral Reef Threats Questions question 1 — IB Biology SL

Using the data, explain the effect of temperature on coral bleaching in the Gulf of Panama.

a. bleaching is zooxanthellae expulsion from coral;

b. high temperature/ $30^{\circ} \mathrm{C} / 32^{\circ} \mathrm{C}$ resulted in loss/death of zooxanthellae (causing bleaching)

OR

negative correlation between temperature and zooxanthellae density OR

positive correlation between temperature and bleaching;

c. photosynthesis in zooxanthellae disrupted which leads to expulsion of zooxanthellae

OR

production of toxic substances which leads to expulsion of zooxanthellae;

2 max

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IB Biology SL D4.3.7 Coral Reef Threats Questions question 1