Marvelously Resilient Coral

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Guest post by Jim Steele

Published October 2, 2019 in California’s Battle Born Media newspapers – the Pacifica Tribune, the Novato Advance, the Sausalito Marin Scope, the Mill Valley Herald, the Twin Cities (Larkspur and Corte Madera) Times, the San Rafael News Pointer and the Ross Valley Herald.

What’s Natural?

Imagine if today’s magnificent coral reefs all dried up and died – from the surface down to a depth of 400 feet. Horrifying! But that was exactly the case 20,000 years ago when growing glaciers of the Last Ice Age lowered sea level 400 feet. Yet coral reefs fully recovered as the earth warmed. So, what makes coral so resilient?

To survive, coral must also withstand lethal effects of modern cyclones, coral-eating crown-of-thorns starfish, and El Niño related bleaching. Rapid growth has allowed most reefs to fully recover within 7 to 30 years. For example, due to the 1998 El Niño event 12 reefs on the Seychelles, experienced greater than 95% mortality. Yet 6 reefs fully recovered within 7-12 years, and within 16 years coral cover had increased by 135% to 305% of pre-bleaching values. The others continued to recover but at a slower pace.

In contrast to climate crisis claims, cyclones cause the greatest coral mortality. Cyclones have caused 48% of lost coral cover, while crown-of-thorns feeding caused 42%, and bleaching just 10%. Yet regardless of cause, coral growth quickly restored most damaged reefs within 10 years. Known as the Phoenix effect, remnant living tissues can expand, regenerating tissue that covers dead skeletons. After several years of regeneration, plus growth of surviving colonies, coral then produce massive amounts of larvae (young coral) and complete the reef’s recovery.

Disturbingly, an extreme advocate of a coral climate “crisis”, Terry Hughes argued global warming has impaired recruitment of new coral to the Great Barrier Reef, despite only 2 years since the 2016 bleaching event. Internet media outlets, eager for ‘click-bait headlines’ wrote, “Great Barrier Reef suffers 89% collapse in new coral” and CNN hyped “Dead Corals Don’t Make Babies”.

But such reduced larval production is normal whenever adult corals are reduced. For example, after a western Australian reef suffered 70 to 90% mortality, larval production was reduced by 96% for the first 6 years. Nonetheless surviving coral increased their abundance by 5-fold over a period of 12 years. After the first 6 years of increasing coral, larval production rapidly increased. Likewise, in the northern Great Barrier Reef, which was heavily bleached in 2016, an 89% decrease in larvae is expected. And consistent with the potential for rapid recovery, surviving coral in the northern Great Barrier Reef have now increased by 16%. Thus, its highly likely we will witness large increases coral larvae within four years.

Media outlets have also misleadingly conflated coral bleaching with dead coral prompting ridiculous headlines proclaiming the Great Barrier Reef is dead. But bleaching is not always lethal. When over 90% of the coral on the Palmyra Atoll experienced bleaching, there was no loss of coral on the reef flats, and only a 9% loss on the fore reefs. Similarly, despite the severe 2016 bleaching in the Coral Sea Marine Park, researchers reported total coral cover was not significantly reduced by 2017. Most bleached corals survived.

Reef building corals depend on energy from photosynthesizing symbiotic algae. But their symbiotic relationship requires careful maintenance. So coral naturally add and subtract symbiotic algae as the seasons change. During the winter, coral increase their symbiotic algae as lower light reduces photosynthesis. Each summer as light intensity increases, they expel symbionts. Bleaching is just an extreme of that behavior. After bleaching, coral can quickly replace their symbiotic algae within days or months with no resulting mortality.

Scientists are increasingly observing that coral can acquire very different symbiotic algae with different genetics. To adapt to changing climates corals don’t require thousands of years to evolve. Coral get instantaneous genetic upgrades simply by acquiring new symbiotic algae. Acquiring different symbiotic algae allowed coral to adapt to dramatic temperature changes as Ice Ages came and went. And acquiring new symbiotic algae now allows coral to rapidly adapt to 60-year changes caused by ocean oscillations.

Under La Niña like conditions, warm water accumulates over the “coral triangle” in the western Pacific, promoting more rains and heavier cloud cover. This condition can dominate for 30 or more years. However, during El Niños as in 2016, that warm water sloshes towards the Americas causing sea levels to dramatically fall. Falling sea levels expose coral to drying winds and shallower bays will more rapidly heat. Furthermore, during an El Niño, the rains and cloud cover moves eastward. With less clouds, the Great Barrier Reef is exposed to more sunshine and more heatwaves. Scientists now recognize a strong connection between ocean heat waves and El Niños. Coral bleaching correlates best with El Niños.

Climate models do not agree on how El Niños will change in the future. But there is good news. Michael Mann, who promotes “dire predictions” due to rising CO2, also published that during past warm periods, the oceans remain in more La Niña-like conditions. And La Niña-like conditions are good for the Great Barrier Reef.

Jim Steele is director emeritus of the Sierra Nevada Field Campus, SFSU and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism.

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48 thoughts on “Marvelously Resilient Coral

  1. We live on a sailboat in the Caribbean June through November. We have seen no bleaching of any significant large areas from Puerto Rico- Bonaire – USVI – to Trinidad. We dive and snorkel everywhere. It seems the entire bleaching hoopla basis may be that we don’t yet know what we don’t know. The largest bleaching was in Bonaire in isolated patches not more than a few hundred square feet. They were all shallow. The destruction from a hurricane is far worse.

    I agree bleaching is likely a natural coping response. Response to massive change must be programmed into corals or they would not be here. It’s certainly easier for small organisms to change than megafauna.

  2. It’s obviously true that coral which can survive ice ages cannot be as fragile as the doom-mongers proclaim.

    But bleached coral does look less pretty and so bleaching does have an impact on the tourism industry.

  3. “20,000 years ago growing glaciers of the Last Ice Age lowered sea level 400 feet. Yet coral reefs fully recovered as the earth warmed.” I would rather say that the reefs migrated. The reefs above the sea level do not survive, but their offspring in the ocean does.

    • I concur.
      “Imagine if today’s magnificent coral reefs all dried up and died – from the surface down to a depth of 400 feet.” is very unlikely to happen.
      It would take an event which dropped the sea level faster than the coral could move down accordingly. I know of no such occurrence. Coral wouldn’t need to ‘recover’ as it was never in any different distress no decline.
      As you suggest coral would simply reduce its uppermost level as sea level reduced and “migrate” down the walls.
      BTW where do these people think coral walls came from?

        • If memory serves, Key Largo has high-stand coral, low-stand coral, and contemporary coral, just for the pleasure of present divers. I was certified NAUI back in the early 1970s.

      • Informative as always. Peter Ridd debunked much of the alarmist junk science on the GBR. It cost him his job. Please consider helping him with his legal fees

    • Uhh, corals are not totally sessile animals. In case I’ve missed a previous enlightenment, I apologize for the redundancy. They have egg stage which become swimmers (plankton) which cruise the ocean blue for a while before settling down on a fixed surface. Oddly enough one of the favorite fixed surfaces is (cupie doll for correct answer) clean dead coral. D…, I hate it when shysters take advantage of well meaning gullibles.

  4. Great article Dr. Steele!

    Only, such a dismal ending; bringing in forever selfish huckster manniacal.

    “But there is good news. Michael Mann, who promotes “dire predictions” due to rising CO2, also published that during past warm periods, the oceans remain in more La Niña-like conditions.”

    Just mentioning it’s name brings darkness and negative connotations to dim the light.

    • Agreed. Every time there is an article here with his smug, piggish face at the top, I want to punch the computer screen. It ends a good article on rather a sour note.

      • I hope you are referring to Mann and not me LOL

        I simply mentioned Mann to my readership so they realize even the czar of dire predictions will contradict apocalyptic headlines

  5. For some reason….people have no problem knowing one plant from the other….ie vegetables you’re trying to grow and weeds….
    …but those same people will group all corals as corals

    Coral reefs are no different than a yard on dry land….some “most” of those corals are flat out weeds…overgrow and smother out the real reef building corals

    • Good analogy Latitude.
      And just as plants have their predators (insects, etc), so do corals (crown of thorns starfish, parrot fish etc)

      Why do CO2 cultists think that nature applies different behaviours to the interactions between species just because atmospheric CO2 goes from 350ppm to 400ppm over a period of 2 centuries, in an experience range that has varied from 120ppm to 4,000ppm?

    • Meadow ecology was always a big hit in biology. {Not is the least because “all-natural” meadows were an easy day-trip from the universities in and around Boston, when the Meadow Ecology fad took off. But that is a story for another day.} In any event, we have a huge amount of data on this environment, particularly when the wildflowers are in bloom. (But that is none of my business.)
      I am sure Latitude could point out for us which species in a meadow are the useful ones and which should be weeded out to preserve the “all-natural” character of the place.

      Latitude would be happy to accompany any of us on a reef expedition (all expenses paid, of course) and explain to us which are the weeds, and which are the valuable cultivars.
      We note for the record that the coral environment is the scene of ferocious competition for space, with tactics up to and including chemical warfare between the participants. There are certainly times and places where fast growing soft corals will dominate. But what holds them in check, long term?
      {We also note for the record that the most important species the reef maintains is the free-spending tourist. This fact alone is a powerful force for the preservation of the reefs.}

      • Tony, you’re not as clever as you think you are….

        I’ll try to make it simple for you….some hard corals build reefs….some hard corals build rubble

          • Rubble is not a stable substrate….it does not build a reef
            Acropora, montipora, etc…..the branching/plating corals..almost all of their bulk is above the reef….they are the weeds…they grow fast and they overgrow and smother out the true reef building corals
            They are the first to move into disturbed areas…..and the first to go when those same areas are disturbed again
            They are the pretty corals…and the worst to use as an indicator of reef health…they’ve colonized a marginal area in the first place

  6. Presumably, when a large area of coral dies off, creatures that predate the coral also die off, which is why in the immediate aftermath, the coral can recover to an extent greater than was present beforehand.

  7. Extinction Rebellion and Greta Thunberg envision a wipe out of corals. IPCC based this on one author.

    https://www.ipcc.ch/2018/10/08/summary-for-policymakers-of-ipcc-special-report-on-global-warming-of-1-5c-approved-by-governments/

    The report highlights a number of climate change impacts that could be avoided by limiting global warming to 1.5°C compared to 2°C, or more. For instance, by 2100, global sea level rise would be 10 cm lower with global warming of 1.5°C compared with 2°C. The likelihood of an Arctic Ocean free of sea ice in summer would be once per century with global warming of 1.5°C, compared with at least once per decade with 2°C. Coral reefs would decline by 70-90 percent with global warming of 1.5°C, whereas virtually all (> 99 percent) would be lost with 2°C.

    “Every extra bit of warming matters, especially since warming of 1.5°C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems,” said Hans-Otto Pörtner, Co-Chair of IPCC Working Group II.

  8. My understanding is that corals along with crinoids, bryozoans, brachiopods, gastropods, and bivalves first appear in the fossil record during Cambrian or Ordovician periods, The greatest “explosion of marine life” in the fossil record was during the Cambrian. A period when for a time atmospheric CO2 levels approached 7,000 ppm. The marine life in the shallow seas that covered much of what is now the United States during that time continued to thrive during the Ordovician period with the atmospheric CO2 levels hanging around 4,000 ppm during most of that period. Can anyone say “ocean acidification’ ? How about “global warming’?

    It was at Versailles State park in SE Indiana where my curiosity about fossils and the natural history of our planet was born during multiple camping trips there and hikes all over the park. Fossils everywhere, but the single greatest concentration is on a hill cut by Fallen Timber Creek where there is a slope over 100 ft high of punky limestone scree where one can pull the fossils out by hand. No rock hammer needed. The first time I pulled a horn coral out of that slope when I was about 8 years old I thought I had found the tooth of the T-Rex of some other dinosaur.

  9. Jim Steele ==> Can you comment on the difference of bleaching effects on shallow reef corals and those at depth — 30 to 400 feet?

    • Hey Kip,

      There are many studies showing that bleaching and mortality decreases with depth. The 2016 Great Barrier Reef mortality was greatest on the most shallow reef crests, consistent with a lower sea level effect. Unfortunately most reports that suggest a reef suffered 90% bleaching only looked at the broad areal coverage but not at depth effects.

      But the research that does look at depth such as Bridge ( 2013). report

      “coral mortality following a severe bleaching event diminished sharply with depth. Bleaching-induced mortality of Acropora was approximately 90% at 0-2m, 60% at 3-4 m, yet at 6-8m there was negligible mortality.”

      https://www.ncbi.nlm.nih.gov/pubmed/24627789

      Studies showing depth zonations in which certain coral species are limited to certain depths, often suggest that at depths lower than 40 meters, many shallow water species will drop out. From that they suggest depth offers a limited refuge from surface warming. However as the Bridge and many others of observed, below 6 meter depths there is often negligible mortality

      • Jim, their focused their sturdy on Acropora…the true ‘weeds’ of the reef
        Acropora grow extremely fast…at least on a coral time line…and colonize and spread like weeds
        They would be the first to colonize a reef that had been damaged…would be the first to get damaged again….and the first to move back in again
        Problem with these bleaching studies…they tend to focus on weeds….and the weeds are just doing what the weeds have been designed to do…colonize marginal areas

        • Lat,

          Indeed species of acropora are “weeds” in the sense they evolved to quickly colonize vacant habitat or quickly recover from a disturbance. They are typically the most abundant species in shallow waters and are most vulnerable to weather. They use their energy to grow instead of storing it for a “rainy day” and are thus the most vulnerable to bleaching. They are also most likely to have the whole colony die when only a portion bleaches and dies

          • Exactly…they are the weeds
            They are the “most vulnerable” because they colonize marginal areas in the first place…and they are the first to go….and the first to move back in when it’s been disturbed

            That makes them the worst indicator of reef health

  10. As I understand it Coral releases eggs every year. Just how long the eggs survive I do not know, but they settle wherever conditions suit them and then grow. So of course any damaged corals will recover over time.
    This is just another Media worthy tool used by the Warners camp to scare us with.

    Regarding the so called “”Weeds”. Remember that a weed is just a plant that we do not want.

    MJE VK5ELL

  11. Nice article.
    The GBR is ~ 2300 km long and is mostly in a north -south orientation.
    Does anyone know of the average seasonal water temperature differences from
    the northern most end to the southern?
    I’m thinking that the coral polyp’s symbionts are different based both depth
    and north-south location (ie temperature dependence).
    If so, is there already more of a temperature gradient now than what
    the Alarmists are predicting for 2100?

    • Bill, I do not recall the precise temperature difference but there have been studies where coral with symbionts from the north are transplanted in the cooler south and die. Most studies report symbionts in the north differ from those in the south

  12. Every time someone says to me that a degree or two increase in ocean water temperatures is going to wipe out the coral reefs, my response is to ask them why, then, are there still healthy coral reefs in the Persian Gulf?

  13. Really good, informative stuff, Jim. Thanks.
    Maybe you can fill me in on a process I’ve always wondered about. On the shallow reefs we surf on in the Indian Ocean, they all have wave damaged flat tops with the living coral growing on the sides of all these deeper channels, about a meter wide, that cut through all over the reef, obviously allowing water flow and nutrients to get to the living coral and allow it to survive. It appears that the coral never blindly keeps growing across the channels, thus choking them and the whole reef. Some process is involved where all the corals mutually refrain from growing across those channels and choking them. Any ideas? Do the polyps have eyes?
    As for bleaching, parts of our local reef at St Leu, Reunion, have bleached every summer for the last 4 decades and recovered each time within a couple of months. St Leu is one of the healthiest and quickest growing reefs in the world, and has amazing variety of different coral species for such a small area, mostly fire coral in the impact zone, which seems to thrive in very shallow water.
    Another thing not mentioned in the GBR reports was any mention of damage being done to the shallow water corals when they are exposed, high and dry, every summer in baking tropical temperatures during spring low tides. It is only lucky, or a fact of its existence, that the lowest tides, when it is exposed completely above water, come around full and new moon when the tide is high at midday, so the coral is not exposed to the severe tropical midday sun, directly overhead as the summer solstice passes over our 21*S position, goes to 23•7*S, then is back directly overhead 2 weeks later, cooking the place a lot longer, in those 4-6 weeks than anywhere closer to the equator. The GBR also suffers the same process. The dying or bleaching of parts of the GBR you mention, especially those seen to be one meter deep on average, may well be explained by it having been exposed above water during the summer spring low tides.
    Weather conditions on those days of exposure may explain the variance of different areas and years.
    I have to also mention the barrier reefs running 2000km up both coasts of Madagascar, especially the west coast which is nearly comparable to the GBR in length and, in some places, width. It is all pristine and in fantastic condition, though the world has been made to believe it is just about extinct and are keen to send troops in to protect it from the Malagasy people who are living off it sustainably, if only because of their lack of technology and its gargantuan, near unlimited size.
    The west coast has daily tidal differences of more than 3 meters due to the fact that the tides arriving in the Mozambique Channel have to go round the huge island and arrive from both the north and south of the island at about the same time, doubling the effect. That means the times of high and low tide arrive about 6 hours later than “normal” and high tide on full and new moons is in the morning and low tide, especially the very low summer springs, occurs at tropical midday, which would really cook it if exposed high and dry. The surfing reefs appear to be generally deeper than those in Mauritius and Reunion, which have only a one meter tide difference, and that may be the reason. Depth is controlled by the height of summer spring low tides. The hollow, best, most tubing waves break on the reefs with the most shallow water, so we are always conscious of the coral depths and conditions, every day out there for decades. It is often only inches deep but the coral remains the same depth for decades, from our observation. The process that limits its upward growth is obvious.
    The recent world media reports about Madagascar being totally ablaze are completely false. All those flying over it recently saw no fires or smoke. There always is some seasonal burning of the long yellow grass as part of land management because they are cattle herders, needing the new green shoots which spring out the ground with the first rains, and the fires are lit just before the rains are expected. If they didn’t burn, their land would quickly revert back to bush, forest or jungle, in many places. Africa is the same and so is Brazil.
    As far as observations on sea level rise goes, the town of St Leu, Reunion, has been a good place to judge because the center of town, 20m from the water, is slightly below sea level and the biggest swells can wash over the beach, onto the main road and spill into town. That can happen 1-3 times per year. Observation over 4 decades has us seeing the waves arrive on the road less often than in the 70s. So, from a place which is the most susceptible to sea level rise, we are noticing less rise, if anything, and certainly see nothing to fear at present. The million year old, 3010m high volcanic island, 50km in diameter, is more likely to be sinking into the crust because of its weight than rising, though the hot spot under the active volcano in its south eastern third may be making it swell and rise in parallel with any sea level rise. Take your pick.
    All the marine biologists I’ve ever questioned, seemed to be unaware that coral reefs only grow in towards the land as the land erodes in time. The best way to explain it to them is that if it grew one centimeter per year, out to sea on the existing coral, an island like Mauritius, maybe 20 million years old, would be 400km wide, instead of it being about 40km. Ancient Madagascar world be the size of Africa, maybe. They all work against beach erosion, for some reason here. As a result, the very shallow barrier reefs, under their control and “protection,” on Reunion’s west coast are slowly filling up with coral bits broken off by the constant big swells, and the lagoons are slowly getting shallower and choking.
    Added to that the installation of a Marine Reserve throughout the whole area of the island’s once totally safe swimming beaches which caused a massive infestation of thousands of giant killer bull sharks, and those who have usurped power over our waters are not very popular here, after 23 major shark attacks since 2011, 11 of them fatal, including 2 children bitten in half, while 9 others lost an arm or leg, or both. A honeymooner was bitten to death in front of his newlywed wife. A 20 year old girl was fatally attacked on Valentine’s Day. A Labrador dog was eaten whole while actually on the beach, dragged back into the water by a monster shark, only a few meters up the beach and not long after 15 year old Sarah was bitten in half in front of her little sister, while snorkeling at the waters edge. It is much worse than the film Jaws, and way, way longer.
    Those running the Reserve continued all these years to deny that the Reserve and its total protection of sharks had anything to do with the attacks concentrated in the Reserve, which had no previous attacks and was safe as a bathtub before. The attacks started 4 years after the Reserve was installed, and continue to this day with next to no one ever in the water. Once these power grabbers get control they hold it at the point of a gun and keep it, no matter what. Their sharks are eating all the Reserve’s biomass, which has not increased after 13 years of total protection, and the shallow, very fragile lagoon, which the Reserve was mainly installed to protect, is now seriously overcrowded because it is the only safe place to swim. At a cost of hundreds of millions, they have presided over and controlled an environmental and economic disaster and a human tragedy of shocking degree and duration, which got worse and worse while they fought control of big shark numbers, refusing to allow any culling. The last 4 attacks have been fatal as the sharks get bigger and more numerous.
    Entry to the water anywhere on Reunion, except inside the little lagoon has been outlawed and policed for the last 6 years, and the fine increased recently. Welcome to the brave new world of human exclusion from nature, and reserved for the elite and those who work for them.
    More than half the island has been made World Heritage, and so, along with the ocean being outlawed, the ecologists in power are now restricting the behavior of the inhabitants who live there and kept it all those centuries good enough to be awarded World Heritage status. Soon the price of entry will restrict it all to only the richest visitors and the “scientists” and their guards.
    Reunion, dictated to by Paris is a blazing example of the Green takeover, way in advance of the rest of the world, and the inhabitants and everyone else are suffering under the regime, while the tourist economy, which you’d expect decent environmental protection would attract, has become non existent except for people visiting family.
    One other note, while I’m at it, is to point out that there is definitely a lack of polar amplification in Antarctica. Seeing that we are sure from the records that polar amplification does always show in a heating or cooling world, it suggests that climate is forced when Antarctica heats or cools. It is its position with that hundred million tons per second current going round it that reduced the Earth’s temperature and made ice form and grow on the planet 15 million years ago, so it obviously dominates the world climate. The world’s heat arrives in the water down there and at the line of convergence gets spun round the globe a few times, its heat never getting anywhere near the pole or ice, and the excess heat is bled to space. If the rest of the world starts heating, the line of convergence moves slightly south but the world doesn’t heat. But if Antarctica heats, for some reason of its own, the rest of the world responds, and likewise if it cools. The answers to what controls world climate will be found by looking in Antarctica.
    As for alarms of any ice breaking off Antarctica, 78mm of precipitation falls on average every year over its enormous permanent ice surface and remains frozen there, which is enough to lower sea level a couple of millimeters a year. Seeing the sea level is not falling every year, we expect a thousand or so cubic kilometers of ice to break off every year, so icebergs the size of small or large state breaking off are only to be expected, as the ice slides into the sea replacing the floating shelves. Just as we expect all China’s black perfectly radiant black ball soot falling on Arctic ice to melt it when the sun shines on it.
    I reckon Antarctic sea ice extent in winter is a big indicator. The latent heat energy exchanges and where it all goes is planetary in its enormity. The Southern Oscillation is best described as the cooling El Niño and the even more cooling La Niña. Evident global affect, everyone agrees. It is a forcing from Antarctica that keeps the world cooler than it was 15 million years ago. Ocean average temperature was 20*C and it is now 6*C.
    Sorry to add all that on which has nothing to do with coral but some of it is simple enough to put doubt in the minds of those sucked in by the scare. Antarctic ice loss and its precipitation, for example, and black soot is always convincing. Arctic melt is their big showcard. Coral bleaching is just a fake power and money grab. Cheers.

  14. Thanks for the post. The current ENSO situation seems a bit unusual — cool water spreading east from S America (La Nina-like), but cool water also prevalent around Australia & southern Indonesia (El Nino-like).

  15. I decided quite some time ago that nature was more intelligent than many humans gave it credit for so this story comes as no surprise to me.

    For those who worry about frosts and planting dates, maybe aligning planting dates with natures signals rather than a solar calendar will lead to less losses? Here in UK, I use signals like the progression of different fruit trees, first leaves to first cut of comfrey, first rhubarb emergence and first pick, first asparagus stalks emerging and first harvest, then appearance of rogue potato tubers not harvested the previous summer.

    Like coral, I find fruit trees are pretty intelligent, so are asparagus crowns, so are potato tubers and actually, so are comfrey plants.

    So I gauge spring by what those plants are telling me, slightly less on what day of the year it is…

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