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Comment by burlesona | Hacker News Reader

Do we have evidence of what happened with coral reefs in earlier historical eras with much lower temperatures?

It’s surprising to me that the corals seem to be unable to survive the 1 degree warming (to date), and troubling because even if we stopped all carbon emissions at this point (IIRC) a 2 degree increase is pretty much guaranteed.

Tragically, I fear it’s already too late for the corals. But I wonder if we have evidence that they can adapt to temperature shifts under the right circumstances, and maybe there’s something we can do to help the ecosystem adapt?

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> Do we have evidence of what happened with coral reefs in earlier historical eras with much lower temperatures?

Some extinctions happened. In most of the other cases, the corals had much, much more time to adapt.

Imagine going 0 to 60 in a minute vs going 0 to 60 in a millisecond. One of those is going to crush you into a paste. We're halfway through that millisecond, watching things get pasted all around us, and trying to figure out if we can somehow stop this process.

Gradual warming and cooling, even to relatively extreme temperatures and CO2 levels by today's standards meant that corals had many, many generations to adjust. Today, not so much.

That’s a helpful analogy, thank you.

It seems that most of the heat impact of global warming is absorbed by ocean waters (https://e360.yale.edu/features/how_long_can_oceans_continue_...) Coral reefs typically live in rather shallow waters (less than 500ft according to wikipedia), because of their dependency of sunlight. So at this depth, there is already a strong daily variation due to day/night cycle, and I imagine a 1 degree average warming on earth is much potentiated in this environment.

Perhaps there is something to be done actively in short term in those environments to prevent this warming, but its so fragile as there are countless interactions between all the microorganisms that I that must be an enormous undertaking, if even possible.

As the oceans warm we can help out by seeding corals in areas that were previously too cool to allow for coral survival. Corals can be easily "fragged" (branches broken off and glued onto other rocks can grow - this is often done in the reef aquarium trade) and moved to areas that are not as warm. Under natural circumstances this kind of migration would take a while but perhaps humans can help speed up the migration into waters with more favorable temps.

That is an interesting idea, however one caveat I see is that the same warming that is killing the corals also changes the ocean currents and heat distribution in ways we can't fully predict yet. I can see this making the site choice difficult.

As a matter of fact, corals themselves provide a lot of historical data in a manner similar to tree growthrings: https://www.ncdc.noaa.gov/news/picture-climate-how-we-can-le...

There are corals that live in warmer waters such as in the Red Sea which has some of the warmest sea water on earth. There are also groups doing research on ways to help corals adapt to higher temperatures [1]

I also wonder if we'll start to see the GBR move south along the coast of Australia as waters that were previously not favorable to corals are now starting to warm.

The other problem in addition to warming is that as CO2 levels rise pH of seawater is going down. Hard corals require a pH that is somewhat alkaline (around 8.3 is ideal).

    [1] https://www.coralvita.co/

The marine fauna has been wiped a couple of times before. Corals will survive (probably), they had seen a few bad times before-

But coral reefs is a different and complex machine. Probably not, or will transform in a totally different structure. What we see now toke three thousands of years to physically develop. If you wipe a reef now, maybe you could expect a return to shape after 500 years. Reefs had survived atomic bombs.

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