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Study finds heat-resistant corals widespread in Palau

By Pacific Island Times News Staff

Heat-resistant corals abound in Palau, largely inhabiting reefs in warmer spots, according to a recent study published by the Palau International Coral Reef Center (PICRC) and the Hopkins Marine Station of Stanford University.

The study, which surveyed 221 colonies of Acropora hyacinthus across 37 reefs sites, found the highest concentrations of heat-resistant corals in the western southern lagoon of Aimeliik State.

“This result could signal that Aimeliik’s reefs will be more resilient to ocean warming than other reefs, and are better prepared to withstand the impacts of climate change,” according to the paper titled Widespread Variation in Heat Tolerance and Symbiont Load are Associated with Growth Tradeoffs in the Coral Acropora hyacinthus in Palau.

The paper, published in the scientific journal eLife, was authored by Brendan Cornwell of Stanford University, and co-authored by PICRC researcher Victor Nestor.

The study identifies heat resistant corals as an important area of research, as these corals are more likely to survive increases in ocean temperature predicted in the coming decades.

As ocean warming drives coral die-off around the world, heat resistant corals could lay the foundation for resilient reefs in the future.

Our survey also found wide variation in symbiont concentration among colonies, and that colonies with lower symbiont load tended to be more bleaching-resistant,” the paper said.

“By contrast, our data show that low symbiont load comes at the cost of lower growth rate, a tradeoff that may operate widely among corals across environments.”

The authors said corals with high bleaching resistance have been suggested as a source for habitat restoration or selective breeding in order to increase coral reef resilience to climate change.

Cornwell and Nestor, however, noted that “the existence of tradeoffs with heat resistance may suggest caution in unilateral use of this one trait in restoration.”

The authors hypothesized that the greatest numbers of heat resistant corals would be found in reef habitats that often experience high temperatures, such as shallow back reefs and intertidal zones. However, heat resistant corals proved to be much more common, and were identified on 24 of 37 sites, including reefs with cooler temperatures.

However, the study also found that heat resistance comes with tradeoffs; corals with higher heat resistance tended to grow more slowly than their heat-sensitive counterparts.

Both growth-rate and heat resistance share a complex relationship with the coral’s symbiont load, or the amount of beneficial microorganisms living in the coral’s tissues. The authors identify this relationship as a topic for further research.

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