Summit County Citizens Voice

Scripps researchers find corals can adapt to cooler oceans temps, but heat kills in the long run

Sponge diversity is high on coral reefs. PHOTO COURTESY NATIONAL PARK SERVICE/A. BOURQE.

Feeding coral polyps. PHOTO COURTESY NATIONAL PARK SERVICE/A. BOURQUE.

By Summit Voice

SUMMIT COUNTY — Along with steady warming of the world’s oceans, temperature extremes have become more common. In 2010, for example, coral reefs in some areas had to survive one of the hottest summers on record, along with record-breaking cold winter temperatures.

To help guide future coral reef conservation efforts, scientists with the Scripps Institution of Oceanography at UC San Diego compared damage to corals exposed to heat as well as cold stress, finding that cool temperatures can inflict more damage in the short term, but heat is more destructive in the long run.

Specifically, former Scripps Oceanography student Melissa Roth and current Scripps scientist Dimitri Deheyn, found corals subjected to cold temperatures suffered greater growth impairment and other measurable damage in just days compared with heat-treated corals.

Yet the researchers found that corals were eventually able to adjust to the chilly conditions, stabilize their health and continue to grow. However, over the long term corals subjected to heat suffered more greatly than those in cold, with evidence of severe bleaching and growth stoppage, a trajectory that leads to death.

The study is published in the Feb. 2 issue of Scientific Reports, a publication of the Nature Publishing Group.

“These results show distinct responses between cold and heat-treated corals on different time scales,” said Roth, now based at Lawrence Berkeley National Laboratory. “On a short time scale, the cold event was actually more harmful to the corals than an equivalent warming event, but over time, these corals were able to acclimate to the cold. Therefore, these corals showed more resilience to seawater cooling than seawater warming.”

The coral’s ability to adjust to cool temperatures surprised the researchers, who say the study’s results highlight the complexities of monitoring coral health in response to varying environmental factors.

During the investigations—conducted inside Scripps’ Experimental Aquarium—the researchers tracked the overall coral health and the stress of their symbiotic algae, sometimes called “zooxanthellae.” The symbiosis is an essential component for reef-building corals because the symbionts provide corals with most of their energy. Accordingly, the researchers found that the cold both disrupted the photosynthetic system of the symbionts and greatly reduced coral growth.

“Global warming is associated with increases but also decreases of temperatures,” said Deheyn, a project scientist in Scripps’ Marine Biology Research Division. “Not much has been known about the comparative effects of temperature decrease on corals. These results are important because they show that corals react differently to temperature differences, which is critical for future management of coral reefs in the realm of climate change.”

Filed under: biodiversity, climate and weather, coral reefs, endangered species, Environment, global warming Tagged: | biodiversity, climate, coral reefs, Environment, global warming, Scripps Institution of Oceanography, sea surface temperatures