Coral bleaching

Definition

Coral bleaching is a phenomenon that occurs when corals lose their vibrant colors and turn white, primarily due to stress from environmental factors such as elevated sea temperatures and ocean acidification. This process happens when corals expel the symbiotic algae known as zooxanthellae, which provide them with food and color. When corals are stressed, they can no longer sustain these algae, leading to weakened coral structures and potentially mass mortality if conditions do not improve.

5 Must Know Facts For Your Next Test

1. Coral bleaching can be triggered by various stressors, including high water temperatures, pollution, and increased solar radiation.
2. Bleached corals are more susceptible to disease, have lower reproductive success, and may face increased mortality if the stressful conditions persist.
3. Even if corals recover from bleaching, the event can cause long-term impacts on reef structure and biodiversity.
4. Coral reefs cover less than 1% of the ocean floor but support about 25% of all marine species, highlighting their ecological importance.
5. Efforts to protect coral reefs include establishing marine protected areas, reducing carbon emissions, and promoting sustainable tourism practices.

Review Questions

• How do environmental stressors lead to coral bleaching and what are the immediate effects on coral health?
  • Environmental stressors like elevated sea temperatures cause corals to expel zooxanthellae, the algae responsible for their color and nutrient supply. This loss leads to the characteristic whitening or bleaching of corals. The immediate effects on coral health include reduced energy intake since they can no longer rely on photosynthesis from the expelled algae. This leaves them vulnerable to disease and can lead to a significant decline in their overall fitness.
• Discuss the relationship between ocean acidification and coral bleaching in the context of reef ecosystem health.
  • Ocean acidification affects coral reefs by decreasing the availability of carbonate ions necessary for corals to build their calcium carbonate skeletons. When combined with elevated sea temperatures that trigger coral bleaching, this creates a double threat to reef health. Bleached corals struggle to recover or rebuild their skeletons due to lower calcification rates caused by acidified waters. This impacts not only the individual corals but also the entire reef ecosystem that relies on healthy corals for habitat and protection.
• Evaluate the effectiveness of current conservation strategies aimed at mitigating coral bleaching events.
  • Current conservation strategies like establishing marine protected areas (MPAs) have shown promise in safeguarding coral habitats by limiting harmful activities such as overfishing and coastal development. However, these strategies need to be complemented by global efforts to reduce greenhouse gas emissions to address climate change effectively. The integration of local management practices with international climate policies is crucial for enhancing the resilience of coral reefs against bleaching events. Additionally, research into coral restoration techniques aims to assist in recovery post-bleaching but must also focus on adapting to changing environmental conditions.

Related terms

Zooxanthellae: Symbiotic algae that live within coral tissues and provide corals with essential nutrients through photosynthesis.

Ocean acidification: The decrease in pH levels of ocean water caused by the absorption of excess atmospheric CO2, impacting marine life, especially organisms with calcium carbonate structures.

Coral reefs: Underwater ecosystems formed by colonies of coral polyps that provide habitat for diverse marine species and protect coastlines from erosion.