By Kenneth Richard on 3. April 2025
Coral reefs expand and thrive as sea levels rise, whereas they undergo millennia of growth hiatuses and “turn-off” or “mass mortality” phases when sea levels fall.
According to a new global sea level reconstruction (Feldman et al., 2025), global sea levels were meters higher than today 7000 to 5000 years ago. Global sea levels fell thereafter throughout the late Holocene.
From approximately 4500 years ago until 640 years ago, previously thriving coral reefs endured “mass mortality” and “turn-off” phases due to incrementally declining accommodation space in the Red Sea region.
This millennial-scale “turn-off” reef growth period was not just limited to this study area, but coral cover decline has been a global phenomenon associated with global sea level fall throughout the late Holocene.
“A global hiatus in coral reef development […] was largely driven by eustatic sea level drop during the late Holocene and caused a lack of vertical accommodation space…”
“In this study, we propose not just a local sea level condition causing specific reef turn-offs or hiatuses, but rather a global phenomenon of sea level fall.”
“A reduction in accommodation space through receding sea levels resulted in mass mortality or sea level constrained corals.”
Considering rising sea levels are advantageous to corals and falling sea levels largely eliminate the potential for growth, future sea level rise may lead to a “significant increase in coral cover”.
“Future sea level rise could provide additional accommodation space for currently sea level-constrained reef systems, potentially leading to a significant increase in coral cover.”
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Image Source: Feldman et al., 2025
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Coral reef growth in the Bikini Atoll lagoon also suffered a very notable hiatus
when they were completely obliterated by 23 nuclear bomb tests between 1946 and 1958.
But they regrew themselves substantially in just 65 years.
Tell me again how “fragile” coral reefs are.
Well they are now Godzilla corals.
Not only are they thriving, they cannot be killed by normal weapons!
Add to that the Amazon Reef, one of the world’s largest reef system, discovered less than a decade ago. It’s located at the mouth of the Amazon River, whose waters really are acidic and water temperatures far warmer than other reef locations. Turns out all the nutrients transported by the river into the Atlantic have far more impact than the water’s pH or temperature.
I’ve fished, swum and dived on coral reefs in many tropical and subtropical waters over my lifetime.
I regard corals as the weeds of the sea floor.
They grow wherever its suits them, some are very attractive, most are very bland, they come in all shapes & sizes and you can’t kill the buggers off completely no matter how hard you try.
Apparently, sea urchins are doing a number on kelp off SE Australia.
I tried sea urchin once at a Japanese restaurant.
I can absolutely guarantee that the sea urchin population worldwide is in no danger of being over consumed by me.
I have no doubts that they pig out on kelp. And not the tender young plants, the gnarly tough bitter old ones.
So, it was warmer during the HCO than it is today, and tropical species such as corals and humans thrived under those conditions?
Inconceivable!
Any warming from the Little Ice Age will kill us all, right soon now!!! So saith the Climastrologists.
Lots of YouTube videos of mysterious population crashes and rapid reductions in China- many cities and rural areas seem emptying. Must be due to AGW. I’m sure we’ll be hearing that soon. 🙂
I wish there was a convention on whether time scale increases left to right, or right to left.
This seems a pretty pointless study. They’ve survived several hundred million years, including the dinosaur wipeout, and ice ages and warmings that kicked sea levels up and down hundreds of meters. Of course they survived whatever happened 6000 years ago!
240 million years ago: The first coral reefs form during the Triassic period.
50-60 million years ago: Modern coral reefs developed during the Eocene epoch.
20-30 million years ago: Coral reefs begin to form complex ecosystems with diverse marine life.
5,000-10,000 years ago: Coral reefs continued to evolve and adapt to changing ocean conditions.
But a little modern warming will kill off all coral and make the earth barren.
Yep and it will be all your fault unless you repent now 🙂
Coral reef disappearance was mostly a tourism encourager….come and see before they’re gone….kind of thing. More people would go see the white cliffs of Dover if they thought they were dissolving away in the acidic ocean….darn I may have started something….expect that in the Guardian soon….
Coral migrates.
When the sea level drops, the coral moves to deeper waters.