Coral bleaching

Definition

Coral bleaching is a phenomenon where corals lose their vibrant colors and turn white, primarily due to stress factors such as rising sea temperatures, ocean acidification, and pollution. This process occurs when corals expel the symbiotic algae (zooxanthellae) that live within their tissues, which provide them with food and color through photosynthesis. Understanding coral bleaching is essential because it highlights the interconnectedness of climate change, marine ecosystems, and human activities.

5 Must Know Facts For Your Next Test

1. Coral bleaching can be triggered by prolonged periods of elevated sea temperatures, typically above 1-2°C over the normal levels.
2. While some corals can recover from bleaching if conditions improve, prolonged stress can lead to coral mortality and the collapse of reef ecosystems.
3. Bleached corals are more susceptible to diseases, making them less resilient to environmental changes and other stressors.
4. Human activities, such as coastal development, pollution, and overfishing, exacerbate the conditions leading to coral bleaching by degrading the overall health of marine ecosystems.
5. Protecting coral reefs through marine protected areas and reducing greenhouse gas emissions are essential strategies for mitigating the impacts of coral bleaching.

Review Questions

• How does rising sea temperature contribute to coral bleaching and what mechanisms are involved in this process?
  • Rising sea temperatures are a primary cause of coral bleaching because they induce stress in coral polyps. When temperatures rise significantly, corals expel their symbiotic zooxanthellae, which provide them with food and color. This loss not only results in the characteristic white appearance but also deprives corals of essential nutrients needed for survival. If high temperatures persist, the likelihood of coral death increases significantly.
• Discuss how ocean acidification impacts coral reefs and contributes to the phenomenon of coral bleaching.
  • Ocean acidification affects coral reefs by reducing the availability of calcium carbonate, which corals need to build their skeletons. Lower pH levels hinder the calcification process, making it more difficult for corals to recover from stress events like bleaching. As ocean conditions worsen due to acidification, corals become increasingly vulnerable to environmental stressors, ultimately affecting their ability to survive and thrive.
• Evaluate the potential long-term effects of coral bleaching on marine ecosystems and human societies that rely on these habitats.
  • The long-term effects of coral bleaching on marine ecosystems can be profound. Coral reefs support a diverse range of marine life and provide essential services like coastal protection and tourism opportunities. As coral reefs decline due to repeated bleaching events, the loss of biodiversity can disrupt food webs and lead to economic losses for communities dependent on fishing and tourism. Furthermore, weakened reefs offer less protection against storm surges and erosion, increasing vulnerability for coastal populations. Addressing climate change and protecting coral ecosystems is critical for maintaining both ecological balance and human livelihoods.

Related terms

zooxanthellae: Microscopic algae that live in the tissues of corals and provide them with nutrients through photosynthesis, playing a critical role in coral health.

ocean acidification: The process by which increased carbon dioxide in the atmosphere leads to higher levels of carbonic acid in oceans, negatively impacting marine life and ecosystems.

thermohaline circulation: The global ocean circulation pattern driven by temperature and salinity differences, which plays a crucial role in distributing heat and nutrients in marine environments.