Trophic strategy and bleaching resistance in reef-building corals

Area of Science:

• Marine Biology
• Ecology
• Climate Change Science

Background:

• Coral bleaching, driven by ocean warming, severely impacts coral reefs by disrupting essential symbiont nutrition.
• The coral host's role in bleaching susceptibility across species remains largely unexamined, despite significant research on symbiont thermal tolerance.

Purpose of the Study:

• To investigate the relationship between coral host traits and bleaching resistance.
• To define autotrophy, heterotrophy, and mixotrophy in corals using stable isotope data.
• To understand how ocean warming affects coral-algal symbiont trophic interactions.

Main Methods:

• Bayesian analysis of carbon and nitrogen stable isotope data.
• Quantification of trophic niche overlap between corals and their symbionts.
• Correlation analysis between niche overlap, polyp size, and bleaching resistance.

Main Results:

• Benchmark values were established to differentiate between autotrophic, heterotrophic, and mixotrophic coral nutritional strategies.
• A negative correlation was observed between trophic niche overlap and both coral polyp size and bleaching resistance.
• Results suggest that corals with less niche overlap (more autotrophic) are more vulnerable to warming oceans.

Conclusions:

• Coral host characteristics significantly influence bleaching resistance.
• Autotrophic corals, previously thought to have a competitive advantage, are disproportionately affected by ocean warming.
• Understanding coral-algal trophic dynamics is crucial for predicting reef resilience in a changing climate.