Heat stress and bleaching in corals: a bioenergetic model

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Physiological Ecology

Background:

• Coral-dinoflagellate symbiosis is vital for holobiont energetics.
• Elevated temperatures cause symbiosis breakdown (dysbiosis), leading to coral bleaching, starvation, and mortality.

Purpose of the Study:

• To extend a dynamic bioenergetic model of coral symbioses.
• To explore mechanisms of temperature impact on symbiosis.
• To simulate thermal bleaching events.

Main Methods:

• Developed a dynamic bioenergetic model of coral symbioses.
• Tested two temperature impact mechanisms: accelerated metabolism and photosynthetic damage.
• Simulated responses to various temperature increases.

Main Results:

• Model captures biological responses to temperature.
• Moderate temperatures increase metabolic rates, decrease photosynthesis, boost symbiont growth, and raise symbiont/host ratio.
• High temperatures cause symbiosis breakdown via photodamage, reduced photosynthesis, and nutrient cycling disruption, leading to bleaching.

Conclusions:

• Coral bleaching is driven by photodamage and nutrient cycling disruption, not solely accelerated metabolism.
• Higher light and DIN increase heat stress susceptibility.
• Heterotrophic feeding enhances thermal tolerance.