Sublethal changes to coral metabolism in response to deoxygenation

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Physiological Ecology

Background:

• Coastal deoxygenation is a significant threat to coral reefs globally.
• Dissolved oxygen (DO) depletion causes hypoxia-induced stress and mortality in corals.
• Coral responses to hypoxia are species-specific and depend on duration and severity of low-DO conditions.

Purpose of the Study:

• To investigate the physiological responses of Caribbean corals to varying levels of deoxygenation.
• To understand the metabolic adjustments corals make to tolerate low dissolved oxygen (DO) conditions.
• To assess the role of metabolic plasticity in coral resistance to deoxygenation.

Main Methods:

• Exposed Caribbean corals (Acropora cervicornis, Porites astreoides, Siderastrea siderea) to severe (1.5 mg L-1 DO), moderate (3.5 mg L-1 DO), and control (6 mg L-1 DO) conditions for two weeks.
• Measured maximum quantum yield (Fv/Fm) to assess photosynthetic efficiency.
• Quantified respiration rates and calculated metabolic budgets (gross photosynthesis to respiration ratio, Pg:R).

Main Results:

• All corals survived two weeks of deoxygenation, but exhibited sublethal metabolic changes.
• Maximum quantum yield (Fv/Fm) was suppressed in A. cervicornis after one week and in S. siderea and P. astreoides after two weeks under deoxygenation.
• Respiration rates decreased in A. cervicornis and S. siderea under severe deoxygenation.
• Metabolic budgets shifted towards photosynthesis-dominance (more autotrophic) in S. siderea and P. astreoides under severe deoxygenation.

Conclusions:

• Corals exhibit species-specific metabolic plasticity to tolerate deoxygenation.
• Metabolic adjustments, such as altered photosynthesis and respiration, are key to coral resistance against low dissolved oxygen (DO).
• Metabolic plasticity is a crucial factor in coral reef resilience to ongoing deoxygenation events.