Coral reefs are a lot more resilient than previously thought. At least according to a new study published yesterday that showed Pacific island coral reef can grow fast enough to match rising sea levels, even with increased ocean temperatures.
Fig. 1: (a) Evidence of stable sea level along the ubiquitous limestone islands of Palau, (b) notches extend approximately 2–3 m horizontally at lowest spring tide (red line, highest tide mark), (c) study sites in Palau, western Pacific Ocean (dark blue, open ocean; pale blue, lagoon; yellow outline, outer reef locations; green, land; tide data from Malakal tide gauge marked with a purple square).
Because they grow vertically on shallow reef flats, researchers observed that Porites microatolls coral is keeping pace with current sea level rise, but may have trouble under the worst-case IPCC scenarios. The Porites microatoll, whose growth is largely lateral and limited by exposure to air, is named for its resemblance to island atolls.
Researchers at the Florida Institute of Technology, who published their study in the Royal Society Open Science, say their findings provide the first evidence that “well-managed reefs will be able to keep up with sea-level rise through vertical growth.” However, if CO2 emissions rise past 670 parts per million (ppm), which may cause ocean temperatures to increase 2.2 degrees Celsius, reefs will have a hard time keeping up with the projected sea level rise.
Currently CO2 levels worldwide are 400 ppm (.o4 percent), but once they cross the 670 ppm threshold, the corresponding rise in ocean temperatures may hamper even a healthy reefs ability to survive. “Reefs will continue to keep up with sea-level rise if we reduce our emission of greenhouse gases,” said Florida Tech’s Rob van Woesik, a professor at FIT’s Department of Biological Sciences and the study’s lead author. “If reefs lose their capacity to keep up with sea-level rise they will drown.”
The study, which focused on Palau island in the western Pacific Ocean, was also co-authored by researchers from the University of Queensland and the Palau International Coral Reef Center. Palau is an island country that is part of the larger Pacific island group of Micronesia and relies on the reef system to break apart storm waves.