Coral bleaching

Definition

Coral bleaching is a phenomenon where corals lose their vibrant colors and turn white due to stressors such as increased water temperatures, pollution, and ocean acidification. This process occurs when coral polyps expel the symbiotic algae called zooxanthellae that live within their tissues, leading to a breakdown in the relationship that is crucial for the corals’ health. The impact of coral bleaching can be profound, affecting marine ecosystems and the livelihoods of communities that depend on healthy coral reefs.

5 Must Know Facts For Your Next Test

1. Coral bleaching can occur when sea temperatures rise just 1-2 degrees Celsius above normal levels for prolonged periods.
2. Once corals are bleached, they are more susceptible to disease, have reduced reproductive success, and may eventually die if conditions do not improve.
3. Coral reefs support about 25% of all marine species, making their health crucial for maintaining marine biodiversity.
4. Human activities such as overfishing, coastal development, and pollution can exacerbate the effects of coral bleaching.
5. Efforts to combat coral bleaching include creating marine protected areas, restoring damaged reefs, and reducing carbon emissions globally.

Review Questions

• How does the relationship between corals and zooxanthellae affect the overall health of coral reefs?
  • The relationship between corals and zooxanthellae is symbiotic; zooxanthellae provide corals with essential nutrients through photosynthesis, while corals offer a protected environment for the algae. When environmental stressors cause corals to expel these algae during bleaching events, the corals lose their primary source of food and energy. This disruption can lead to weakened coral health, decreased growth rates, and increased susceptibility to disease, ultimately threatening the entire reef ecosystem.
• What are some human activities that contribute to coral bleaching, and how can these be mitigated?
  • Human activities such as pollution from agricultural runoff, coastal development, and overfishing contribute significantly to coral bleaching. These practices can increase nutrient levels in water, leading to harmful algal blooms and altering the delicate balance of reef ecosystems. Mitigation strategies include implementing sustainable fishing practices, establishing marine protected areas to limit human impact, and reducing pollutants entering ocean waters through better land management practices.
• Evaluate the long-term consequences of widespread coral bleaching on marine biodiversity and coastal communities.
  • Widespread coral bleaching has severe long-term consequences for marine biodiversity as it leads to habitat loss for countless marine species that rely on coral reefs for shelter and food. As reefs decline, fish populations that depend on healthy ecosystems also suffer, resulting in diminished catches for local fishermen. Additionally, coastal communities that rely on tourism associated with vibrant reefs face economic challenges as reef degradation impacts their livelihoods. Ultimately, the loss of coral reefs due to bleaching threatens not only marine life but also the cultural and economic stability of communities around the world.

Related terms

zooxanthellae: Microscopic algae that live in the tissues of coral and provide them with essential nutrients through photosynthesis.

ocean acidification: The process by which the ocean becomes more acidic due to increased carbon dioxide absorption, negatively impacting marine life, particularly organisms with calcium carbonate structures.

marine biodiversity: The variety of life forms in marine ecosystems, including different species of plants, animals, and microorganisms, which can be threatened by coral bleaching.