Living Coral Reef: Heat Stress, Bleaching and Recovery over 50 Years

What is Coral Bleaching?

Coral bleaching occurs when corals expel the symbiotic algae (zooxanthellae) living within their tissues, causing them to turn completely white. This process is triggered by environmental stressors, primarily elevated sea temperatures.

Bleached corals are more vulnerable to disease and death, as they lose a crucial source of nutrition from these algae.

The Role of Ocean Warming

Ocean warming leads to increased water temperature, which can cause coral bleaching. The degree heating weeks (DHW) metric quantifies the cumulative heat stress experienced by corals over time.

When DHW exceeds a certain threshold, it triggers widespread bleaching events that can significantly impact reef health.

Recovery and Resilience

Coral recovery is influenced by various factors including water quality, nutrient availability, and the presence of other organisms like grazing fish. Grazing fish play a critical role in maintaining algal balance on the reef.

If conditions improve, corals can recover from bleaching through a process known as recolonization, where new coral polyps settle and grow over dead or damaged areas.

Light Absorption and Depth

As light intensity decreases with depth due to Beer-Lambert absorption, corals in deeper waters receive less energy from photosynthesis, affecting their health and growth.

This phenomenon highlights the importance of water clarity and depth for coral survival.

Frequently asked questions

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