Mediterranean Corals Revived After Lethal Ocean Warming

While diving in the Spanish Mediterranean sea, Diego K. Kersting, a researcher at the Freie University of Berlin and the University of Barcelona, discovered that Mediterranean corals, thought to be dead after lethal ocean warming episodes, revived.

That was the first time in history when scientists observe corals regrow after heat stress previously killed them. Diego K. Kersting issued details on the discovery, along with the study on it, in the journal Science Advances on Wednesday.

Kersting and the study’s co-author, Cristina Linares, have been monitoring 243 colonies of the threatened Mediterranean corals since 2002. They previously stated, in some papers, that most of the coral colonies present signs of mortality due to heat stress caused by massive ocean warming episodes.

“At some point, we saw living polyps in these colonies, which we thought were completely dead. It was a big surprise,” stated Diego K. Kersting for AFP.

Mediterranean Corals Revived After Lethal Ocean Warming

Hundreds of polyps, some tiny organisms, form what we know as corals. These polyps produce a hard exoskeleton of calcium carbonate. Corals live in symbiosis with algae. When heatwaves hit coral reefs, it either fries the polyps or disrupts the symbiosis between corals and algae. This event translates into what scientists call “coral bleaching.”

In 2003, 25 percent of the Mediterranean coral near Spain coastline died due to extreme ocean warming episodes. But, according to Kersting, the polyps of these corals came up with a survival mechanism. They shrunk, abandoned their exoskeletons, and created new colonies from scratch. This process has never been observed in corals.

“For sure, it’s good news, but what we see now in the Mediterranean Sea and other parts of the world is that these marine heatwaves are recurrent – happening every summer or every second summer,” explained Diego K. Kersting.

“So if you are having every second summer a heatwave, and it’s killing 10 to 15 percent of the cover, I mean, the numbers are clear. They actually need help from us. We need to stop climate change because it’s not going to be enough,” he added.