Coral bleaching

Definition

Coral bleaching is a phenomenon where corals lose their vibrant colors and become white due to stress factors, primarily caused by elevated water temperatures, pollution, and ocean acidification. This process occurs when corals expel the symbiotic algae, known as zooxanthellae, that live within their tissues and provide them with energy through photosynthesis. When stressed, corals can lose these algae, leading to diminished energy, weakened health, and potential mortality if conditions do not improve.

5 Must Know Facts For Your Next Test

1. Coral bleaching events are becoming more frequent due to global warming, with temperature increases of just 1-2 degrees Celsius being enough to trigger bleaching.
2. Bleached corals are not dead yet; they can recover if normal conditions return quickly, but prolonged bleaching can lead to coral mortality.
3. The Great Barrier Reef has experienced severe bleaching events in 2016 and 2017, highlighting the vulnerability of coral reefs to climate change.
4. Certain species of coral are more resistant to bleaching than others, showcasing the importance of biodiversity for resilience in reef ecosystems.
5. Human activities such as overfishing, coastal development, and pollution exacerbate the stress on coral reefs, making them more susceptible to bleaching.

Review Questions

• How does coral bleaching impact the biodiversity of tropical marine ecosystems?
  • Coral bleaching severely impacts the biodiversity of tropical marine ecosystems because corals serve as the foundation for these habitats. When corals bleach and lose their symbiotic algae, they become less healthy and can die off if stress continues. This decline in coral health reduces available habitat and food for many marine species that rely on reefs for shelter and sustenance. As a result, the overall diversity and stability of these ecosystems diminish.
• In what ways does the El Niño phenomenon contribute to increased occurrences of coral bleaching?
  • The El Niño phenomenon contributes to coral bleaching by raising ocean temperatures significantly across vast areas of the Pacific Ocean. These elevated temperatures disrupt the delicate balance necessary for coral health and can lead to widespread bleaching events. During an El Niño event, warmer waters can persist for extended periods, making corals more susceptible to stress. This connection highlights how natural climate variability interacts with long-term climate change effects on marine ecosystems.
• Evaluate the implications of ocean acidification on coral reefs in relation to coral bleaching events.
  • Ocean acidification significantly affects coral reefs by lowering the availability of carbonate ions needed for corals to build their calcium carbonate skeletons. This reduction in structural integrity makes corals more vulnerable to stressors like temperature increases that cause bleaching. Additionally, when corals are bleached due to high temperatures, their ability to recover is hindered by acidified waters, as weakened corals struggle to regenerate their skeletons. Thus, ocean acidification exacerbates the impacts of coral bleaching and threatens reef survival.

Related terms

Zooxanthellae: Photosynthetic algae that live symbiotically within coral tissues, providing corals with essential nutrients and color.

Ocean acidification: The decrease in pH levels of ocean water due to the absorption of excess atmospheric CO2, impacting marine life and ecosystems.

Tropical marine ecosystems: Ecological communities located in warm, shallow waters near the equator that support diverse marine life, including coral reefs.