Discovery of the region of “super corals”

AUSTIN, Texas – In 2019, a professor of hydrology at the University of Texas at Austin undertook a research project to see if he could identify harmful nutrients circulating in groundwater in a delicate coral reef sanctuary in the Philippines. . He achieved this goal, but following the long history of accidental scientific discoveries, he instead stumbled upon something completely unexpected: a region of possible “super corals” that thrive despite high levels of carbon dioxide.

Results based on 2019 fieldwork were published in August in the journal ACS ES&T Water.

For the first time, UT Austin professor Bayani Cardenas and a team of international researchers were able to attribute the source of CO₂ and other gases and nutrients in the seawater there to the groundwater, a finding that the researchers say shows just how vulnerable the underwater reef environment can be to how communities discharge sewage, agricultural runoff and other by-products into the sea.

“This is an invisible vulnerability,” said Cardenas, a professor in the geological sciences department at UT Jackson School of Geosciences. “We were able to show with this site that groundwater is part of these delicate environments of coral reefs. There is a connection, and it is still not as accepted in science and in many parts of the world. “

More than that, Cardenas said the research has led to new questions – and new research proposals – about the super corals they found that could be replicated elsewhere in the years to come as the global CO₂ the levels are expected to increase.

Coral reefs have long suffered from climate change, most notably during a global coral bleaching event from 2014 to 2017 that caused heat stress to 75% of the world’s reefs, according to the American Meteorological Society. Yet the area of ​​coral that Cardenas studied in the passage of Verde Island in the Philippines, a region so dynamic and diverse that he calls it “the Amazon of the ocean”, thrives despite the large amounts of CO. .₂ pumped from groundwater.

Lead author Rogger E. Correa, a researcher at Southern Cross University in Australia, estimated that groundwater pumps about 989 grams of CO₂ per square meter per year in the area they studied, known as “Twin Rocks” and bordering a chain of volcanoes. It’s the equivalent of parking two cars on the seabed and letting them emit carbon dioxide for a full year on every hectare of reef.

To distinguish groundwater from seawater, scientists have submerged devices that measure CO levels₂ and radon-222, a naturally occurring radioactive isotope found in local groundwater but not in ocean waters. The measurement technique was developed by co-author Isaac Santos, professor at the University of Gothenburg in Sweden.

This work follows a 2020 study conducted by Cardenas where he discovered CO₂ bubbling from the seabed off an area of ​​the Philippine coast so dramatically that it has nicknamed it “Soda Springs”.

The end result of the latest survey is an entire region of coral reefs that needs to be studied more closely, said Cardenas, who is a geoscientist and not a coral researcher.

Adina Paytan, a researcher at the Institute of Marine Sciences at the University of California at Santa Cruz, who was not associated with the study, warned that other human-induced stressors, including sedimentation, overfishing and pollution, can still doom coral reefs. But she was encouraged by the fact that the Cardenas team showed that corals can grow in high carbon environments, a finding that “gives some hope for the future of corals.”

Co-authors of the study included researchers from the Leibniz Center for Tropical Marine Research (ZMT) in Germany; the State Office for Mines, Energy and Geology in Germany; and the following institutions in the Philippines: Ateneo de Manila University, Agricultural Sustainability Initiatives for Nature Inc. and Planet Dive Resort.