wunder beta🪸 Coral Bleaching and Ocean Acidification
Understand why warming and CO₂ stress coral reefs, and the science-backed efforts giving reefs a fighting chance.
What you’ll learn
- The Living ReefExplain that coral is a living animal that partners with algae, and describe how heat stress causes bleaching.Reefs are built by living coral polyps that partner with tiny algae called zooxanthellae, which photosynthesise and share food, giving coral its colour. When coral is stressed, especially by warm water, it expels these algae and bleaches, turning white and starving, though it can recover if the stress eases.
- A Changing SeaExplain ocean acidification as CO₂ dissolving to lower pH, and describe hopeful efforts to help reefs.The ocean absorbs much of the CO₂ from burning fossil fuels. That CO₂ reacts with seawater to form a weak acid, lowering pH in a process called ocean acidification, which makes it harder for coral and shellfish to build shells. Scientists are fighting back by breeding heat-tough corals, replanting reefs, and cutting emissions at the source.
Questions this course answers
What actually builds a coral reef?
A reef is built by tiny animals called coral polyps, whose limestone skeletons pile up over centuries into vast structures.
What do the algae called zooxanthellae give the coral?
The zooxanthellae photosynthesise and share the food they make with the coral, and they also give the coral much of its colour.
What is coral bleaching?
When coral is stressed, often by warm water, it expels its algae, leaving the white skeleton visible, which is bleaching, and the coral is left starving.
What causes ocean acidification?
When the ocean absorbs CO₂, the gas reacts with seawater to form a weak acid, lowering the water's pH, which is ocean acidification.
On the pH scale, where does absorbing extra CO₂ push seawater?
Absorbing extra CO₂ lowers seawater's pH, nudging the naturally slightly-basic sea down toward the acidic end of the scale.
Why is a more acidic ocean a problem for coral and shellfish?
More acidic water makes it harder for coral and shellfish to build their limestone shells and skeletons, which can even weaken and dissolve.
Grounded in trusted sources
- NOAA
- Smithsonian Ocean
- National Geographic
- Woods Hole Oceanographic Institution
Every Wunder lesson is built from real, reputable sources — never invented.
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