Corals Grow To Be Much, Much Older Than Previously Assumed, Research Finds — Implications Relating To Ocean Acidification & Coral Bleaching Events

Specific coral genotypes (“individuals”) can live for more than 5,000 years (at the least) according to new research from the National Marine Fisheries Service, Penn State, and Dial Cordy & Associates.

The findings — based on research focused on elkhorn corals (Acropora palmata) living around Florida and in the Caribbean — mean that corals are probably one of the very longest living animals in the world currently.

Clouds of reef fish and corals, French frigate shoals, NWHI

What that means is that when you see mass coral bleaching events in the Great Barrier Reef, for instance, what you are actually seeing is the mass death of animals that have been alive since before 3000 BC (some of them anyways).

Animals that have been alive since anything very similar to the language you speak, and the beliefs you hold, even existed. And, also, when your own ancestors were very likely living in a different part of the world then you are now (periodic mass migrations are a constant of the history of the last 10,000 or so years).

What’s particularly interesting about the research is that, owing to the way that many corals sometimes “reproduce” by fragmenting, the largest corals aren’t necessary the oldest — as some had previously supposed. Indeed, determining age simply by observing the size the of the coral colony/skeleton in question doesn’t seem to be possible. For some species anyways.

The new findings are also important because of the implications they may hold with relation to ocean acidification and anthropogenic climate change. Ocean acidification is already having a very negative effect on coral reefs, in conjunction with warming waters and increasing levels of waterborne pathogens, but as the ocean’s waters continue acidifying many coral reefs around the world will likely simply dissolve — as they won’t be able to build their skeletons fast enough to counteract dissolution.

“Our study shows, on the one hand, that some Acropora palmata genotypes have been around for a long time and have survived many environmental changes, including sea-level changes, storms, sedimentation events and so on,” stated Iliana Baums, associate professor of biology, Penn State. “This is good news because it indicates that they can be very resilient. On the other hand, the species we studied is now listed as threatened under the US Endangered Species Act because it has suffered such sharp population declines, indicating that there are limits to how much change even these very resilient corals can handle.”

Ocean acidification, it should be noted, isn’t really something that can be adapted to anyways, as oceanic waters that aren’t supersaturated with the minerals necessary for skeletal or shell growth can’t support lifeforms such as corals, oysters, and various types of phytoplankton anyways.

There may well be some types, and/or locations, that will manage to persist, but generally speaking worsening climate change and ocean acidification spells death and bleaching for most of the world’s coral reefs, and the coral animals living in these skeletons/colonies themselves (and their photosynthetic algae symbionts).

“Previously, corals have been aged by investigating the skeletons of the colonies or the sizes of the colonies,” Baums continued. “For example, bigger colonies were thought to be older. However many coral species reproduce via fragmentation, in which small pieces break off from large colonies. These pieces look like young corals because they are small, but their genomes are just as old as the big colony from which they broke. Similarly, the big colonies appear younger than their true age because they became smaller during the process of fragmentation.”

The press release provides details: “Now, for the first time, Baums and her colleagues have used a genetic approach to estimate the ages of corals. The method determines when the egg and the sperm originally met to form the genome of the coral colonies. The researchers then tracked the number of mutations that accumulated in the genome since that time. Because mutations tend to arise at a relatively constant rate, the researchers were able to estimate an approximate age in calendar years of the coral genomes in their study.”

The findings of the approach are that, as mentioned at the start of this article, Acropora palmata genomes local to the coasts of Florida and to the Caribbean have been around for more than 5,000 years.

Which makes you wonder how long they can live for?

“This was surprising, as previously, only cold-water corals were found to be older than 1,000 years,” stated Baums. “Knowing the age of individuals in a population is important for understanding their population history and whether the population is increasing or decreasing. It is especially important when the population under study is threatened.”

“If Acropora palmata genomes have persisted over hundreds to thousands of years, it implies persistence through substantial environmental changes, and possibly gives hope that they can survive additional anticipated climate change. What is different now is that human-induced climate change (and ocean acidification) is happening at a rate that far exceeds past environmental changes. Therefore, the coral’s past ability to survive environmental change does not necessarily predict their future success.”

The new findings are detailed in a paper published in the journal Molecular Ecology.

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