Coral bleaching

Definition

Coral bleaching is a phenomenon where corals lose their vibrant colors and turn white due to stress, often caused by elevated sea temperatures, pollution, or ocean acidification. This process occurs when corals expel the symbiotic algae, known as zooxanthellae, that live within their tissues and provide them with nutrients and color. The loss of these algae not only affects the health of the corals but also has cascading effects on marine ecosystems and biodiversity.

5 Must Know Facts For Your Next Test

1. Coral bleaching occurs when water temperatures rise by just 1-2 degrees Celsius above normal levels for an extended period.
2. Bleached corals can recover if conditions improve, but prolonged stress can lead to coral death and ecosystem collapse.
3. Pollution from agricultural runoff, plastics, and sewage can exacerbate the effects of climate change on coral reefs.
4. Coral reefs support about 25% of all marine species, making their health critical for global biodiversity.
5. Some coral species are more resilient to bleaching than others, leading to shifts in community composition as environmental conditions change.

Review Questions

• How does the process of coral bleaching affect marine ecosystems?
  • Coral bleaching significantly impacts marine ecosystems by disrupting the balance of life within coral reefs. Since corals are home to a wide variety of marine species, their loss affects not just the corals themselves but also the fish and invertebrates that rely on them for shelter and food. As coral reefs degrade, the habitat loss can lead to a decline in fish populations and biodiversity overall, further destabilizing these ecosystems.
• Discuss the primary stressors that lead to coral bleaching and how they interact with each other.
  • The primary stressors that lead to coral bleaching include elevated sea temperatures, pollution, and ocean acidification. Higher temperatures cause corals to expel zooxanthellae, leading to bleaching. Simultaneously, pollution from runoff introduces harmful substances that can weaken corals and increase susceptibility to stress. Ocean acidification further complicates this by impairing the corals' ability to build their calcium carbonate structures, making them more vulnerable to environmental changes.
• Evaluate the long-term implications of coral bleaching on global biodiversity and human communities dependent on marine resources.
  • The long-term implications of coral bleaching on global biodiversity are profound as coral reefs support around 25% of all marine life. Their degradation could lead to significant species loss and reduced genetic diversity. For human communities that rely on fishing and tourism associated with healthy coral reefs, this translates into economic challenges and food insecurity. The decline in reef health could disrupt local economies and cultural practices tied to marine ecosystems, highlighting the urgent need for conservation efforts.

Related terms

zooxanthellae: Symbiotic algae that live within coral tissues and are essential for coral health, providing nutrients through photosynthesis.

ocean acidification:

The decrease in pH levels of the ocean due to increased carbon dioxide absorption, which negatively impacts marine organisms, especially those with calcium carbonate structures.

marine ecosystem: A complex network of living organisms and their physical environment in ocean waters, including coral reefs, which are vital for biodiversity.