Coral bleaching

Definition

Coral bleaching is a phenomenon where coral polyps expel the symbiotic algae (zooxanthellae) living in their tissues, resulting in a loss of color and essential nutrients. This process typically occurs in response to environmental stressors like elevated water temperatures, pollution, or changes in salinity, and can have devastating effects on marine ecosystems and the communities that rely on them for livelihood.

5 Must Know Facts For Your Next Test

1. Coral bleaching can lead to widespread mortality of coral reefs, which are vital habitats for many marine species.
2. The frequency of coral bleaching events has increased significantly over the last few decades due to climate change and rising sea temperatures.
3. While some corals can recover from bleaching if conditions improve, prolonged stress can lead to irreversible damage and the loss of entire reef systems.
4. Bleached corals are more susceptible to disease, further threatening their survival and the health of the ecosystem.
5. Coral reefs support over 500 million people globally through fisheries, tourism, and coastal protection, making their health crucial for human communities.

Review Questions

• How does elevated sea temperature contribute to coral bleaching, and what mechanisms are involved in this process?
  • Elevated sea temperatures cause stress to corals, leading them to expel zooxanthellae, the algae that provide them with energy. This expulsion results in the white appearance of bleached corals since they lose their color without these symbiotic organisms. The mechanism behind this involves the breakdown of the mutualistic relationship between corals and zooxanthellae when stressed, which is often triggered by prolonged high temperatures.
• Discuss the broader implications of coral bleaching on marine biodiversity and human communities that rely on coral reefs.
  • Coral bleaching has significant implications for marine biodiversity because coral reefs are home to a large variety of marine species. When reefs degrade due to bleaching, it leads to habitat loss for many fish and invertebrate species, disrupting entire food webs. Human communities also suffer since they depend on healthy reefs for food, tourism, and coastal protection. The loss of coral reefs can therefore threaten both ecological balance and economic stability for these communities.
• Evaluate the effectiveness of current conservation strategies aimed at mitigating coral bleaching and their potential impact on future reef health.
  • Current conservation strategies include establishing marine protected areas, restoring damaged reefs, and promoting sustainable fishing practices. While these efforts can help mitigate some immediate threats, their effectiveness in addressing climate change—which is a primary driver of coral bleaching—is limited. To have a lasting impact on future reef health, these strategies must be integrated with global initiatives aimed at reducing greenhouse gas emissions and promoting sustainable development to ensure that reefs can withstand environmental stressors.

Related terms

zooxanthellae: Microscopic algae that live in the tissues of coral, providing energy through photosynthesis and contributing to the coral's vibrant colors.

ocean acidification: The decrease in pH levels of the ocean caused by the absorption of excess carbon dioxide from the atmosphere, which can weaken coral structures.

marine biodiversity: The variety of life forms in marine ecosystems, including different species of fish, invertebrates, and plants that depend on coral reefs for habitat and resources.