[Coral-List] So you think you understand coral bleaching?
Scott Wooldridge
swooldri23 at gmail.com
Thu Mar 26 02:53:00 UTC 2020
Hi Doug,
I see you are well versed in the dogmatic response of coral bleaching. Therefore, my challenge for you, is to answer 3 very basic questions. Question 1: Can non-symbiotic (hermatypic) corals survive at 33-34 deg Celsius? Question 2: Can the photosymbionts (zooxanthellae) that associate with corals survive at 33-34 deg Celsius when free-living or in culture? Question 3: Can the coral-algae symbiosis survive at 33-34 deg Celsius?
I can supply you with the references if need be. But the answers are YES, YES, very rarely (most commonly NO).
So is the heat stress problem due to the Host, the Symbiont or the Symbiosis ?
I am not talking about extreme scenarios of warming. But even in saying that. I am not convinced AT ALL that the conclusions of the Hughes et al. study are correct nor WISE. Namely, their claim that the corals died quickly from boiling water temperatures. Indeed, my facetious mention of the crude coral bleaching model mentioned in my last post was a direct reference to this claim, whilst trying to remain politically correct - opps. But really let’s take a step back and think scientifically. So they are confident of their claim because they followed the energetic status of the symbiosis in the 6 week lead up to the event? No they didn’t. They observed the event outcome (visual bleaching) and then attributed the response to the heat metric accumulation they wanted to justify their beliefs!!
PLEASE PLEASE everyone take note and read the paper below. The warmest year on the GBR as recorded by satellite-derived SST was in 2004. It was warmer than the event recorded by Hughes et al. And guess what? There was minimal bleaching in that year. Also minimal mortality as recorded by Ray Berkelmans(AIMS). But what? Shock horror!! The nutrient status of the GBR for 2004 was extremely oligotrophic. No big flood (drought period) and no upwelling. Well isn’t that just dandy.
https://www.researchgate.net/publication/332658613_An_enigmatic_decoupling_between_heat_stress_and_coral_bleaching_on_the_Great_Barrier_Reef
This result will NEVER be promoted to the media or general public because of the political ramifications. But it is also why I think the light-weight unjustified conclusions of Hughes et al. have been so very damaging. Lets be honest, this is why most scientist have jumped on board the “oh we can do nothing but yell loudly at the importance of mitigating warming’. Let me be clear, I am not against efforts to reduce global warming. it will be needed. However, I am totally against the notion that coral bleaching is a CORALS BOILING in HOT WATER scenario.
For another recent example of how nutrients interact with warming to predict bleaching resistant versus sensitive sites - have a look at the nice study done in Moorea.
https://phys.org/news/2020-02-nutrient-pollution-coral-resist.html
oh what ?they say high nutrients basically DOUBLES the severity of bleaching....exactly what I have found for the GBR, as detailed in the manuscripts below.
https://www.researchgate.net/publication/223780705_Water_quality_and_coral_bleaching_thresholds_Formalising_the_linkage_for_the_inshore_reefs_of_the_Great_Barrier_Reef_Australia
https://www.researchgate.net/publication/26826520_Improved_water_quality_can_ameliorate_effects_of_climate_change_on_corals
https://www.researchgate.net/publication/308746785_Excess_seawater_nutrients_enlarged_algal_symbiont_densities_and_bleaching_sensitive_reef_locations_1_Identifying_thresholds_of_concern_for_the_Great_Barrier_Reef_Australia?_sg=cvY9BxKoCv3-dVfb5Xcl2HjBJa2-E70DKNBBY4XJzz3CmdHoKtlKKfUdez6xvHOWUYnKDt5MRHvK6iI3s4K0x96AclkfRF1cB9R5ecqp.IobbN_h9xORD3L_w2TmHMYos9MIWM5du52F5OcSFhzGqIGjhl0R5JjgbI_E8uSHPs5nZFsS-sLTqoN-YAk7W-A
https://www.researchgate.net/publication/308746844_Excess_seawater_nutrients_enlarged_algal_symbiont_densities_and_bleaching_sensitive_reef_locations_2_A_regional-scale_predictive_model_for_the_Great_Barrier_Reef_Australia?_sg=cvY9BxKoCv3-dVfb5Xcl2HjBJa2-E70DKNBBY4XJzz3CmdHoKtlKKfUdez6xvHOWUYnKDt5MRHvK6iI3s4K0x96AclkfRF1cB9R5ecqp.IobbN_h9xORD3L_w2TmHMYos9MIWM5du52F5OcSFhzGqIGjhl0R5JjgbI_E8uSHPs5nZFsS-sLTqoN-YAk7W-A
I challenge people to read this last paper. The regional-scale predictive model for the GBR. Get a reality check on the value of the NOAA DHW product is for predicting and explaining coral bleaching patterns. By itself, it is very poor. But fantastic when you integrate with it predictions of nutrient status, and some way of making the heat stress relate to absolute temps - not just relative accumulations of anomaly heat.
But the key for future studies - if that will be of great importance - They must be working at the FRONT END of event to get the true story.
For your consideration,
Scott
Sent from my iPad
> On 26 Mar 2020, at 9:25 am, Douglas Fenner <douglasfennertassi at gmail.com> wrote:
>
>
> Scott,
> Thank you for this interesting perspective. Of course learning more about the mechanisms of the relationship between zooxanthellae and the host coral animal, and the onset of bleaching is a good thing. I don't think anyone would argue with that.
> I note that in one of your review papers, that you write that "...the onset of the bleaching syndrome and setting of upper thermal bleaching limits are emergent attributes of the coral symbiosis...which is known to depend not just on temperature, but also external (seawater) nutrient availability and zooxanthellae genotype." I have no quarrel with that. We could also add light intensity, which is well documented to exacerbate bleaching (Coelo et al, 2017), and reduced water circulation (Nakamura, 2001, 2003). There may be other additional factors as well. There are, of course, differences between the temperature threshold for bleaching of the coral symbiosis with zooxanthellae, and the threshold for mortality for a bleached coral with 1% or less of it's original zooxanthellae still in it. Those are two different things, and I would argue that coral mortality is far more damaging to coral reef ecosystems than coral bleaching. Corals can, if the temperatures don't get too high, recover from bleaching and be back to normal in most ways in a year or two and life can go on. Damage to the ecosystem is far greater when large numbers of corals die.
> You want people to "go for the gold" of a "cure." The use of the word "cure" sounds like what people use when they talk about disease, but as far as I can tell, you're not saying that bleaching is caused by an infectious agent (though some may be, there is literature documenting that for one species of coral in the Mediterranean).
> There is a difference between a "cure" and "treating the symptoms." With the common cold, we can treat symptoms, but not the cause of the cold (viruses). So what is the ultimate cause of bleaching? Nutrients? Bad zooxanthellae genotypes? Do nutrients by themselves cause bleaching and colony death if the water is not unusually hot? I haven't heard of that, correct me if I'm wrong. The world has several thousand atolls that exist in oligotrophic tropical warm seas, with flourishing corals, which can, and have been, killed by high water temperatures, not by nutrients. In 1998 and 2014-17, about 90% of the corals in the Chagos archipelago were killed by hot water-induced bleaching, though coral populations recovered considerably in between. Only one of those atolls has any people on it, there are only tiny islands, and some of the atolls have no islands at all, NO terrestrial nutrient inputs, and corals were bleached and killed there just like they were near to high islands and continents elsewhere when temperatures got to high. Are the genotypes of zooxanthellae that corals naturally have causing bleaching outbreaks even when the water is not unusually hot? Haven't heard of that one, and it would have some explaining to do to account for why bleaching occurs in mass events in particular locations instead of continually everywhere.
> The article you refer to by Santos et al has an interesting sentence in the abstract, the second sentence: "Coral reefs have been devastated by warm water temperatures at a rapid pace and currently, there is no effective method to predict a mass bleaching event." Apparently the NOAA Coral Reef Watch project is a total waste of money, all those maps of where the water is hot, hotspots, degree heating weeks, all that stuff is a total waste of time and money, according to that sentence. That sentence flies in the face of an awful lot of empirical evidence, it appears to me. Perhaps they meant something else, if they did, they needed to state it in a way that it couldn't be misinterpreted. Because taken literally, it is dead wrong, and a mountain of evidence shows that.
> Why am I picking on that? Because your "go for the gold" is implying that the "cure" for bleaching is in the mechanisms in the coral leading up to bleaching, not in hot water and global warming. What is the main ultimate cause (not proximal cause) of mass coral bleaching mortality? (that's the thing we need to avoid more than anything else to save corals and reefs, isn't it?? Or is it best just to treat symptoms when you can treat the ultimate cause? When doctors have a choice between those two, they don't neglect the ultimate cause, because if they do, they can lose their patient. If we do, we could lose our patient, the coral.) Isn't the ultimate cause global warming with temperature spike events caused by El Nino and other ocean heatwaves??
> How about nutrients, if high nutrients were the primary ultimate cause, SST's (sea surface temperatures) would not be good predictors of bleaching and NOAA Coral Reef Watch would never have gotten any traction or funding, nor would anyone pay any attention to what they put on the web. Can it be better refined? Surely, what can't be? Is there more to learn? Surely. BUT, it is the best current predictor of bleaching. And that is because higher temperatures do indeed cause bleaching, it is a primary cause, though other things can exacerbate it, like high light levels, reduced water motion, and nutrients. (Of course, other things than high temperatures can cause coral bleaching, but most mass bleaching events correlate well with high SST's.)
> You write that "the conceptual coral bleaching model adopted by most-all coral reef scientists is WRONG; which at its crudest, explains coral bleaching in terms of corals BOILING TO DEATH in hot water." OK, so high temperatures don't kill corals??? Fact is, and it is a fact not an opinion, every living thing has a maximum temperature that it can survive in. That includes humans. "Heat exhaustion" and "Heat stroke" are two stages in the human response to limiting temperatures for humans. Go beyond that, and human die. Take any other organisms, every organism, and heat it, and when the temperature is high enough, it will die. There are NO exceptions. Limits differ for every organism. The highest limits are for what are called "thermophyles" which are microbes that can live in water just below boiling, you can find them in hot springs in places like Yellowstone National Park in the US. Heat them a degree or two higher, and they die (I'm not up on the study of them around deep sea vents, there may be some that can survive even higher temperatures there). But the high temperature thresholds for most organisms are vastly lower than that, and for most the limit is not a lot higher than what they normally experience, which has been documented for corals as well. Actually, there are many statements, particularly in the popular literature, that corals which die from bleaching die when they have been bleached for a long time, because they have lost their major source of energy, the zooxanthellae, so they in essence starve to death. My memory tells me there are papers documenting loss of energy reserves in corals that have been bleached for long times. Further, there are papers that document that corals can't sexually reproduce for at least a year after bleaching, surely because they don't have the energy reserves. All makes sense. However, as Hughes et al (2018) have pointed out, in the recent bleaching events on the GBR (Great Barrier Reef in Australia), corals died so fast after bleaching that they surely didn't die of starvation. “These widespread losses were not due to the attrition of corals that slowly starved because they failed to regain their symbionts. Rather, temperature-sensitive species of corals began to die almost immediately in locations that were exposed to heat stress” (Hughes et al. 2018). So what did they die of??? High levels of nutrients? Not likely, why would they only die when the water is hot? They died because they were too hot. The zooxanthellae and the coral animal cells are two different organisms. They both have maximum temperatures they can survive, and those high temperature thresholds don't have to be the same. Further, you can kill a coral with hot water without it bleaching. Try dropping a living coral into boiling water. Will it bleach first?? Or just die? Doesn't much matter whether the coral has color when you drop it in, or is already bleached and has no zoox left. It will be scalded and die very quickly indeed. If a human touches a red hot hot plate, the skin cells will be killed extremely fast, we call that a "burn" and humans that have large burn areas are in serious danger of death.
> The fact that when temperatures are high enough, bleaching can happen quickly is captured in the "degree heating weeks" threshold, that works better than just a single temperature threshold, for predicting mass coral bleaching. The higher the temperature, the faster mortality occurs, as illustrated by the finger on the red hot plate, but also fits with the "degree heating week." Further, the fact that when high temperatures cause corals to bleach, if the temperature recedes the corals can survive and regain their zoox, but if the temperature goes higher the coral dies, means that the coral animal, with few zoox left, is sensitive to additional rises in temperature, which if they happen kills the coral, if they don't happen the coral doesn't die. So the mortality of a coral that has lost 99% of it's zoox depends heavily on temperature, too high and it dies, not too high and it doesn't die. Only a bit more than 2 C above average summer high temperatures (no where near boiling).
> I contend that the evidence indicates that coral mortality following bleaching can be from high temperatures (but likely can also be from very extended bleaching due to loss of energy supplies, though I'm not sure the evidence for that is ironclad. I don't pretend to be an expert on the subject). I wrote my arguments in my paper "Coral reef myths and misconceptions. Reef Encounter 34: 30-37." See Myth #5: "Bleached corals die of starvation." http://coralreefs.org/wp-content/uploads/2020/02/REEF_ENCOUNTER_Dec_2019_lo-res_3.pdf
> So I think your statement that the common view that corals die from boiling fails on two accounts, first that you haven't demonstrated that that is the common view, and second that the question is not whether it is literally BOILING that kills them, but whether a slight increase of a degree or two above the mortality threshold for the animal is what kills it, and the evidence does support that at least at times that is what kills them.
> In summary, I have no quarrel with the details of your hypotheses about bleaching mechanisms, or the opportunities to discover more about bleaching mechanisms, nor the possibility that might lead to some way of producing more temperature-tolerant corals. More research on those things is a good thing. I caution that it is a huge leap from producing a temperature-tolerant coral in an aquarium to making all the world's corals temperature tolerant. I don't think anyone knows how to do that, I haven't read the people who are selecting for temperature tolerance to produce "super corals" claim to be able to do that, I haven't heard of anyone selecting temperature tolerant corals in reef restoration claim to be able to do that. You want us to "go for the gold" but that is surely the "gold" for such efforts. Maybe someone will come up with a way, one of those bright young people, surely we should be thinking about how to do that. But we don't have a way to do that yet and it doesn't look like an easy problem to solve, and that's not the thing you're urging people to think about.
> BUT, you are essentially playing down the need to reduce and stop global warming, even though it is the main ultimate cause of mass coral bleaching and death. We need to do that not only to save corals and reefs, but also to save terrestrial environments from things like fires (Australia, California, Amazon being examples), and from the world becoming so hot that 10's if not 100's of thousands if not more, people die in heat waves, and parts of the planet become uninhabitable by humans. We don't lack for reasons to stop global warming, and corals are part of that but only part of the reasons. There is NO conflict between doing that and researching the mechanisms that cause coral bleaching. Also, there is NO conflict between the need to reduce global warming, and the need to reduce local threats like nutrients, sediment, overfishing, disease, etc etc.
> Cheers, Doug
>
> Coelho, V., Fenner, D., Caruso, C., Bayles, B., Huang, Y., Birkeland, C. 2017. Shading as a mitigation tool for coral bleaching in three common Indo-Pacific species. Journal of Experimental Marine Biology and Ecology 497: 152-163.
>
> Hughes TP, Kerry JT, Baird AH, Connolly SR, Dietzel A, Eakin CM, Heron SF, Hoey AS, Hoogenboom MO, Liu G, McWilliam MJ, Pears RJ, Pratchett MS, Skirving WJ, Stella JS, Torda G (2018) Global warming transforms coral reef assemblages. Nature 556:492– 496
>
> Nakamura, T., van Woesik, R. 2001. Water-flow rates and passive diffusion partially explain differential survival of corals during the 1998 bleaching event. Marine Ecology Progress Series 212:301–304.
>
> Nakamura, T., et al, 2003. Water flow facilitates recovery from bleaching in the coral Stylophora pistillata. Marine Ecology Progress Series 256: 287-291.
>
>> On Tue, Mar 24, 2020 at 11:34 AM Scott Wooldridge via Coral-List <coral-list at coral.aoml.noaa.gov> wrote:
>> Dear Coral Listers,
>>
>>
>>
>> I think it is fine that the reef science community discusses strategies
>> that can help formulate new ways of doing (and reporting) our science that
>> can help minimize our carbon footprint. But can I suggest that we owe the
>> global public and the coral ecosystems themselves so much more than this.
>>
>>
>>
>> Like those scientists tasked with finding a vaccine for COVID-19, we need
>> to keep challenging ourselves to find the CURE for coral bleaching. This
>> must consume 99.9% of the best thinking time of coral reef scientists. And
>> before we resign ourselves to believing that reducing global carbon
>> emissions (and by inference future sea temperatures) is the sole solution
>> we can offer the global public, I believe we need to double down on our
>> efforts to understanding the suite of cellular processes that initiate
>> coral bleaching, especially those at the FRONT END of the bleaching
>> response.
>>
>>
>>
>> By FRONT END I mean those processes that happen in the days-weeks before we
>> see any visual sign of bleaching (i.e. symbiosis breakdown). They are
>> subtle, not well studied, and not well understood. But when you start to
>> investigate them more deeply, you quickly realize that the conceptual coral
>> bleaching model adopted by most-all coral reef scientists is WRONG; which
>> at its crudest, explains coral bleaching in terms of corals BOILING TO
>> DEATH in hot water.
>>
>>
>>
>> The issue I specifically draw your attention to in this post, is the
>> little-known FACT that the endosymbiont population increases its size and
>> growth rate (as measured by cellular division rate) in the days and weeks
>> of warming leading up to the visual coral bleaching response. THEREFORE,
>> immediately before the break down of the symbiosis, the endosymbionts are
>> by our best measures very happy, and by adding some anthropomorphism -
>> think that the symbiotic lifestyle cannot be much better.
>>
>>
>>
>> Don’t believe this? Don’t take my word for it. It has been very well
>> reported by others, most recently;
>>
>>
>>
>> https://www.researchgate.net/publication/331593854_Effects_of_increased_heat_on_fluorescence_and_dinoflagellate_density_in_the_captive_coral_Anthelia_sp
>>
>>
>>
>>
>> And obviously, given my intent to get people thinking about the science of
>> the response, I have already had my say on this issue.
>>
>>
>> https://www.researchgate.net/publication/307695433_Breakdown_of_the_coral-algae_symbiosis_Towards_formalizing_a_linkage_between_warm-water_bleaching_thresholds_and_the_growth_rate_of_the_intracellular_zooxanthellae?_sg=-2o85tlB6whC-hSPB0t8oWFed2eECtwPxvsoVRgGKUmzu6k0TIDq5aSV6BwcOhlLqeiGGYr3KAwOMLqI2UkuYtNLnddwaWcl1ReDnhNh.pvBbZTSCSahzvcVu-JkqhLKf-zq1EbYJ6GquHXoR2Nfs2G8--J5_4bxKPwNXk0lfNXJmGnuvk3srT7GzoZSkmQ
>>
>>
>>
>> https://www.researchgate.net/publication/44644540_Is_the_coral-algae_symbiosis_really_'mutually_beneficial'_for_the_partners?_sg=j-rvYFlYazoFU-eah3oORE-zhln-XE-Rt9sIsBFdHrjKHFWO3E1jvDuSBJmwoJ97CP1_RYFtuY-gXbicnyXyRuLK-0gAgwvn2XMNqukP.Mdg_vAKy_Zgedumry2ZUKz9kDoEj6KH_K84VDQ57AebVQnp8oLXLx95adt-cwLzuRjJ2I-j5St_pcMDr-2jtEA
>>
>>
>>
>>
>> All these articles ULTIMATELY explain coral bleaching in terms of a loss of
>> host control of the demographic parameters of its endosymbiont population.
>> This is very far from the CORALS BOILING IN HOT WATER conceptual model. And
>> that is good news!! Since it provides hope, that if we can limit the
>> thermo-kinetic growth potential of the endosymbionts, whilst simultaneously
>> retaining their capacity to release fixed carbon, we may be well on the way
>> to understanding what constitutes a BLEACHING RESISTANT coral. Much more
>> testing needs to be done on this issue. For example, can this favorable
>> symbiotic condition be achieved by ensuring a severe limitation of the
>> seawater supply of nutrients, such that the symbiont doesn’t have access to
>> the prerequisite nitrogenous material needed for cellular division, even
>> during thermo-kinetic events that promote increased division? Or, do we
>> need to look/find/evolve a new type/species of endosymbiont, most likely
>> one with a bigger cellular diameter, that will have a slower thermo-kinetic
>> division rate?
>>
>>
>>
>> There are so many questions. Still unknown. Still unconsidered. Still
>> untested.
>>
>>
>>
>> My challenge, especially to all the fresh thinking young scientists out
>> there, is to keep an open mind. Keep striving for the CURE. Never let
>> yourself be convinced that we already know all the necessary science to
>> answer this. WE DON’T and we are so very very far from it….
>>
>>
>>
>> And finally, for a bit of comic relief as well as encouragement I am
>> forever drawn to the excited words of an old Australian swim coach, who
>> famously stated STUFF THE SILVER, WE CAME FOR THE GOLD. For those old
>> enough to remember, he orchestrated a brilliant tactical race for his
>> swimmer to beat the best simmers in the world at the 1988 Olympics. The
>> SILVER in coral bleaching research is to be content to quibble about the
>> relative merits of ways to reduce our global carbon footprint. We need to
>> refocus, go back to the beginning and keep searching for a CURE. Or in the
>> words of the excited swim coach STUFF THE SILVER, GO FOR GOLD.
>>
>>
>>
>> https://www.youtube.com/watch?v=zgGr-quFf2k
>>
>>
>>
>> For your consideration,
>>
>>
>> Scott Wooldridge
>> _______________________________________________
>> Coral-List mailing list
>> Coral-List at coral.aoml.noaa.gov
>> https://coral.aoml.noaa.gov/mailman/listinfo/coral-list
>
>
> --
> Douglas Fenner
> Lynker Technologies, LLC, Contractor
> NOAA Fisheries Service
> Pacific Islands Regional Office
> Honolulu
> and:
> Consultant
> PO Box 7390
> Pago Pago, American Samoa 96799 USA
>
> "Already, more people die from heat-related causes in the U.S. than from all other extreme weather events."
> https://www.npr.org/2018/07/09/624643780/phoenix-tries-to-reverse-its-silent-storm-of-heat-deaths
>
> Even 50-year old climate models correctly predicted global warmng
> https://www.sciencemag.org/news/2019/12/even-50-year-old-climate-models-correctly-predicted-global-warming?utm_campaign=news_weekly_2019-12-06&et_rid=17045989&et_cid=3113276
>
> "Global warming is manifestly the foremost current threat to coral reefs, and must be addressed by the global community if reefs as we know them will have any chance to persist." Williams et al, 2019, Frontiers in Marine Science
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