Coral reefs in the eastern Pacific could survive into the 2060s

Scientists at the University of Miami’s Rosenstiel School of Marine, Atmospheric and Earth Science have found that some reefs in the tropical Pacific could sustain high coral cover through the second half of this century by mixing the symbiotic algae that host them. The findings offer a bright spot in an often bleak picture of the future of coral reefs around the world.

As global warming leads to the loss of coral reefs around the world, scientists believe some corals are increasing their heat tolerance by altering the symbiotic algal communities that house them, which provide the energy they need to survive through photosynthesis.

“Our results suggest that some reefs in the eastern tropical Pacific, which include the Pacific coasts of Panama, Costa Rica, Mexico and Colombia, may be able to sustain high coral cover into the 2060s,” the coral biologist said Ana Palacio-Castro, lead author of the study, a graduate of the Rosenstiel School and a postdoctoral fellow at the school’s Cooperative Institute for Marine and Atmospheric Studies. “While this could be considered good news for these reefs, their survival may not last beyond this date unless we reduce global greenhouse gas emissions and global warming at a larger scale.” »

The shallow coral reefs of the eastern tropical Pacific Ocean are formed primarily by branching corals of the genus Pocillopora, which are extremely important to the region’s reefs. The microscopic algae they harbor in their tissues harvest light to help corals produce energy for their growth. The loss of these symbiotic algae results in the coral turning white or bleaching and the coral struggling to meet its energy needs, which can often prove fatal.

To better understand how corals have improved their tolerance to thermal stress, the researchers examined more than 40 years of monitoring data from Panama’s coral reefs, one of the longest datasets of its kind in the world. They analyzed temperature, coral cover, bleaching and mortality data from three ocean heatwaves — 1982-1983, 1997-1998, and 2015-2016 — as well as algal symbiont community data over the last two.

Analysis showed that the 1982-83 heatwave significantly reduced coral cover on the reef, but the impacts of the 1997-98 and 2015-16 El Niños were milder, particularly for Pocillopora coral — sometimes known as cauliflower coral — the predominant reef . Structure of Corals in the Eastern Tropical Pacific. They also confirmed that during periods of intense ocean heatwaves, the heat-tolerant alga Durusdinium glynnii becomes more prevalent in this particular lineage of corals, making them better able to withstand periods of high temperatures. Combined with climate projections for future heat stress, reefs composed primarily of Pocillopora coral and harboring this heat-tolerant alga proved better equipped to survive and maintain high coral cover well into the second half of the century, suggesting that that some reef systems may be more resilient to warming than previously thought.

“This study shows that there are unusual reefs that could survive for several decades thanks to their ability to mix symbionts,” said Andrew Baker, professor of marine biology and ecology at the Rosenstiel School and lead author of the study. learn. “While we don’t think most reefs can survive in this way, it suggests that what remains of our current reefs may persist longer than we previously thought, although there may be far fewer species.” Coral reefs are incredibly valuable natural resources. Provide assets, coastal protection and fishing benefits and support many local communities. We can still make a difference by protecting them.

The study was supported by grants from the National Science Foundation (NSF) (OCE 1447306 and OCE-1358699) and the COLCIENCIAS Fellowship for Doctoral Study Abroad (#529).