Widespread oxyregulation in tropical corals under hypoxia

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Physiological Ecology

Background:

• Coral reefs face increasing hypoxia due to ocean deoxygenation from pollution and warming.
• Oxygen regulatory capabilities are key to hypoxia tolerance in aquatic life but are largely unknown in corals.

Purpose of the Study:

• To investigate the oxygen-consumption patterns and oxyregulatory capabilities of various coral species under declining oxygen partial pressure (pO2).
• To determine if corals exhibit oxyregulatory or oxyconformity behaviors.

Main Methods:

• Measured oxygen (O2) consumption rates across 17 coral species exposed to progressively lower pO2 levels.
• Quantified total positive regulation (Tpos) and maximum regulation effort (Pcmax) for each species.

Main Results:

• All 17 coral species demonstrated the ability to oxyregulate, refuting the idea that corals are simple oxyconformers.
• Significant variation in oxyregulatory capacity (Tpos) was observed among species, ranging from 0.41 to 2.42.
• Corals achieved maximum regulation effort (Pcmax) at approximately 30% air saturation and showed regulation down to <10% air saturation.

Conclusions:

• Corals possess significant oxyregulatory capabilities, challenging previous assumptions of oxyconformity.
• Oxyregulation is likely a critical survival mechanism for corals in dynamic, hypoxic shallow reef environments.
• Understanding coral oxyregulation is vital for predicting reef resilience to climate change and anthropogenic impacts.