Back from the dead: Some corals regrow after 'fatal' warming

In this undated photo released by Science Advances, Cladocora caespitosa coral polyps are seen underwater near the Columbretes I
In this undated photo released by Science Advances, Cladocora caespitosa coral polyps are seen underwater near the Columbretes Islands in the Mediterranean Sea

For the first time ever, scientists have found corals that were thought to have been killed by heat stress have recovered, a glimmer of hope for the world's climate change-threatened reefs.

The chance discovery, made by Diego K. Kersting from the Freie University of Berlin and the University of Barcelona during diving expeditions in the Spanish Mediterranean, was reported in the journal Science Advances on Wednesday.

Kersting and co-author Cristina Linares have been carrying out long-term monitoring of 243 colonies of the endangered reef-builder coral Cladocora caespitosa since 2002, allowing them to describe in previous papers recurring warming-related mass mortalities.

"At some point, we saw living polyps in these colonies, which we thought were completely dead," Kersting told AFP, adding it was a "big surprise."

Coral are made up of hundreds to thousands of tiny creatures called polyps that secrete a hard outer skeleton of calcium carbonate (limestone) and attach themselves to the .

Heat waves kill these animals—by either essentially roasting them alive or causing them to eject the symbiotic algae that live within them and provide them nutrients, thus leading to coral bleaching.

A quarter of the coral cover of Spain's Columbretes Islands was lost to a particularly extreme heat wave in 2003.

  • For the first time ever, scientists have found that some corals that were thought to have been killed by heat stress have recove
    For the first time ever, scientists have found that some corals that were thought to have been killed by heat stress have recovered
  • Back from the dead: Some corals regrow after 'fatal' warming
    3D computed tomography section of a rejuvenated Cladocora caespitosa corallite. It can be seen how the rejuvenated polyp grew back to its original size after shrinking its dimensions and started budding. Credit: Diego K. Kersting

Time running out

But the researchers found that in 38 percent of the impacted colonies, the polyps had devised a survival strategy: shrinking their dimensions, partly abandoning their original skeleton, and gradually, over a period of several years, growing back and starting a new skeleton.

They were then able to gradually re-colonize dead areas through budding.

In order to be sure the polyps were in fact the same animals staging a comeback, rather than new coral created through sexual reproduction, the team used 3D computer imaging to confirm the old, abandoned skeleton was connected to the new structure.

This process of "rejuvenescence" was known to exist in the fossil record but had never before been observed in coral colonies that exist today.

Kersting said the finding opens up the intriguing possibility that other modern corals around the world—such as those in Australia's dying Great Barrier Reef—might be applying similar survival strategies, though further investigation is required.

  • In this undated photo released by Science Advances, a Cladocora caespitosa reef is seen underwater near the Columbretes Islands
    In this undated photo released by Science Advances, a Cladocora caespitosa reef is seen underwater near the Columbretes Islands in the Mediterranean Sea
  • The discovery means there is a narrow window of opoprtunity to prevent coral reefs from going extinct as a result of climate cha
    The discovery means there is a narrow window of opoprtunity to prevent coral reefs from going extinct as a result of climate change

It also meant that there was a narrow window of opportunity to prevent coral reefs, vital ecosystem engineers that provide shelter for hundreds of species of fish and plants, from going extinct as a result of climate change.

"For sure, it's good news, but what we are seeing now in the Mediterranean Sea and other parts of the world is that these marine heat waves are recurrent—happening every summer or every second summer," Kersting said.

These corals also grow very slowly—at a rate of about 3 millimeters a year—"so if you are having every second summer a heat wave, and it's killing 10 to 15 percent of the cover, I mean, the numbers are clear," he added.

"They actually need help from us. We need to stop , because it's not going to be enough."


Explore further

Rapid coral death and decay, not just bleaching, as marine heatwaves intensify

More information: D.K. Kersting at Freie Universität Berlin in Berlin, Germany el al., "Living evidence of a fossil survival strategy raises hope for warming-impacted corals," Science Advances (2019). DOI: 10.1126/sciadv.aax2950 , https://advances.sciencemag.org/content/5/10/eaax2950
Journal information: Science Advances

© 2019 AFP

Citation: Back from the dead: Some corals regrow after 'fatal' warming (2019, October 9) retrieved 20 October 2019 from https://phys.org/news/2019-10-dead-corals-regrow-fatal.html
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User comments

Oct 09, 2019
So simple warming is not fatal after all? This (re)budding is likely how they developed in the early warm days of evolution to begin with. So the cooler oceans were the offensive force in their lives.

Oct 09, 2019
Depends on what scientific study you read this week. I've recently read another study saying it's chemicals leaching from land. Still needs to be corrected but this is not necessarily caused by global warming. This researcher probably lost funding for printing this article.

Oct 09, 2019
@Porgie
@JamesG.

Why do you two make it so obvious that you are nothing but denialist trolls working for the Russian/GOP/Fossil funded troll-factories? It's obvious because you ignored the point: that RECURRING ocean water heatwaves will soon enough make them go extinct due to ongoing/increased warming, as they will soon no longer have time to recover between heatwave events. If by some unlikely chance you two are genuine in your opinions, and are not paid trolls and 'weaponised stupids' doing this for free, then please in future consider ALL the facts being presented, rather than just kneejerking to partially informed assertions which make it quite clear you are ill-informed and/or prejudiced denialisms instead of reasonable, objective thinking, human beings. Good luck to us all. :)

Oct 09, 2019
ps: The way it's going in Australia's Great Barrier Reef coral colonies, the warming events are already becoming so frequent/extensive that we have resorted to 'reseeding' selected areas in the more devastated areas with coral segments from remaining areas not so severely affected due to being slightly outside the worst-affected zones.

Oct 09, 2019
""For sure, it's good news, but what we are seeing now in the Mediterranean Sea and other parts of the world is that these marine heat waves are recurrent—happening every summer or every second summer," Kersting said."

Yes. Hot summers happen every summer, and of course, summers are a recurring season with hot temperatures. It would be far more surprising if there were COLD recurring summers. That would not be too good for the growing season, now would it?
Certain microbial type life forms are said to thrive in very hot seawater next to volcanos. How did these life forms happen to survive in almost boiling water? Perhaps a little bit of Evolution and reprogramming by adaptation did the trick? Who knows?

Oct 09, 2019
Some corals regrow after 'fatal' warming


otherwise coral would never have survived the Paleogene-Eocene thermal maximum.

Oct 10, 2019
The mystery is still out however as to how shoot the potty miss (antigorcle) sockpuppet and his other puppets above are so stupid to be used as trolls by Russian/GOP/Fossil funded troll-factories making a complete idiot of himself everyday LOL

Oct 10, 2019
otherwise coral would never have survived the Paleogene-Eocene thermal maximum.


The Malthusian catastrophists have NO argument, so they resort to stupid ad hominem attacks. Rage on, fools. The fact is coral has survived for eons. The planet is cooler than "normal" now, and has been for most of the past million years. The alarmist fools have to explain how life survived at all ... but they can't because their theory is based on political science, not the scientific method. Life evolved under much warmer conditions than now; it was several degrees warmer only 140,000 years ago. It's ridiculous to suggest Life is going to end as global temps rebound toward "normal."

Oct 10, 2019
Anonym seems to have been smoking some of that anonymous weed...again ;)

Oct 14, 2019
A line from the Jurrasic Park movie that is very true: "Life will find a way".

Oct 14, 2019
Anonym seems to have been smoking some of that anonymous weed...again ;)
Jeebus, perpetuating the refer madness stigma is harmful to those who derive a medicinal benefit from it, if you only knew. Please respond again, but with some science -- was it several degrees warmer 140K years ago or wasn't it? Corals first appeared in the Cambrian period, ~535 million years ago. They seem to have adapted to the temperature swings of the planet's climate during all that time fairly well?

Oct 14, 2019
@Protoplasmix.
Corals first appeared.... They seem to have adapted to the temperature swings of the planet's climate during all that time fairy well?


Yes, but how long did they have to adapt; and how many perished in the meantime? Humans are not corals; they don't take kindly to being sacrificed en-masse while some of us survive long enough to adapt and repopulate. In any case, the change now is so relatively sudden, and may soon trigger the tipping point where overwhelming outgassing from long-naturally-sequestered carbon/methane/CO2 will take that change to a whole new and extreme level of suddenness which we will be lucky to survive in enough numbers to 'adapt' at all. By saving the corals/other life that were adapted to the tolerable pre-AGW conditions (which favoured humanity and its civilisations/agriculture) we can save ourselves the ordeal of going through OUR very own 'extinction' event which may not leave many (if any at all) of us to 'adapt and repopulate'.

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