Coral bleaching

Definition

Coral bleaching is a phenomenon where coral polyps expel the symbiotic algae (zooxanthellae) living within their tissues, leading to a loss of color and vital energy sources. This process can occur due to various stressors such as increased water temperature, pollution, and ocean acidification, and it has significant implications for marine ecosystems and human activities reliant on healthy coral reefs.

5 Must Know Facts For Your Next Test

1. Coral bleaching can occur when water temperatures rise just 1-2 degrees Celsius above normal levels for an extended period.
2. When corals bleach, they become more susceptible to disease and mortality due to the loss of their primary food source from zooxanthellae.
3. Bleached corals may recover if stress conditions subside and if zooxanthellae return, but prolonged bleaching can lead to widespread coral death.
4. Climate change is a major driver of coral bleaching events, with rising global temperatures causing more frequent and severe bleaching occurrences.
5. Coral reefs are crucial for biodiversity, serving as habitats for numerous marine species and contributing to the livelihoods of millions of people worldwide.

Review Questions

• How does increased water temperature contribute to coral bleaching, and what are the immediate effects on the coral ecosystem?
  • Increased water temperature leads to coral bleaching by causing corals to expel their symbiotic algae, zooxanthellae, which provide them with essential nutrients and color. The immediate effect of this stressor is the loss of vibrant colors, leaving corals white and vulnerable. As a result, bleached corals can suffer from reduced growth rates, weakened immune systems, and higher susceptibility to diseases, ultimately affecting the entire ecosystem that relies on healthy coral reefs.
• Discuss the long-term implications of coral bleaching on marine biodiversity and human economies that depend on coral reefs.
  • The long-term implications of coral bleaching are dire for marine biodiversity as the loss of corals disrupts habitats for numerous fish species and other marine organisms. This decline in biodiversity can lead to imbalanced ecosystems and a decrease in the resilience of marine environments. For human economies, particularly those relying on tourism and fisheries, the degradation of coral reefs results in lost income opportunities and reduced food security, making it essential to address the underlying causes of bleaching.
• Evaluate potential strategies that can be employed to mitigate coral bleaching and support reef recovery in a changing climate.
  • To mitigate coral bleaching and support recovery efforts, several strategies can be employed. These include establishing marine protected areas to reduce human impacts, restoring degraded reef habitats through active replanting of corals, and improving water quality by reducing pollution. Additionally, addressing climate change through global efforts to reduce greenhouse gas emissions is crucial. Research into breeding heat-resistant coral species may also provide long-term solutions for enhancing resilience in future warming scenarios.

Related terms

Zooxanthellae: Microscopic algae that live in symbiosis with coral polyps, providing them with food through photosynthesis and contributing to the vibrant colors of coral reefs.

Ocean Acidification: The process by which the ocean becomes more acidic due to increased levels of carbon dioxide, affecting marine life and particularly harming coral reefs.

Ecosystem Services: The benefits provided by ecosystems to humans, such as coastal protection, tourism, and fisheries, which are heavily reliant on healthy coral reef systems.