[Coral-List] Fwd: So you think you understand coral bleaching?

Douglas Fenner douglasfennertassi at gmail.com
Fri Apr 3 22:52:30 UTC 2020

      I'd been thinking that maybe some of your posts that I responded to
had some exaggerations.  I actually exaggerate fairly frequently in
conversations, because of just what you are saying, taking things to the
the extreme or logical conclusion often illustrates the point more vividly,
and people understand better.  In conversations, I try to always follow my
exaggerations by saying something like "I'm exaggerating here of course,
but exaggerating is fun and sometimes useful."  I want people to know that
I know that I'm exaggerating, and that I don't think the exaggeration is
literally true, it's done for didactic purposes.
      I take the 99.9% comment in that vein.  I was going to reply that
putting 99.9% of all your eggs in one basket and is a super risky thing to
do.  My guess is that funding agencies realize this, so even though one
thing may seem the most promising, they fund several of the top things, to
hedge their bets and be sure to fund at least a few that pan out.
      I completely agree that promising scientific ideas and leads like
yours should be funded and pursued, and find it hard to imagine that anyone
in their right might would not want to do that.  And encouraging young
people to think big and think outside the box and aim high is a very good
       Further, I agree with the idea of "going for the gold."   To me, the
biggest prize, the gold, is saving coral reef ecosystems.  Steve and  I
agree, I think, that the saving coral reefs will require, necessarily,
avoiding the worst of global warming and climate change.  We're glad to see
you agree.  We just get distressed when people act like that's not a
       My point was I thought that corals could die from high temperatures
quickly, if the temperatures are high enough, and that people who say they
die of starvation imply that is the only way they die, and while I wouldn't
be at all surprised if they die that way sometimes I think they can also
die quickly from it just being way too hot.
       I interpret Ross Jones' papers as showing that and going beyond what
I was guessing, to show that bleaching and coral mortality are two
separate, and separable things.  If they get too hot they can die quickly
after bleaching or even before bleaching.  Bleaching is not necessary to
produce mortality from high temperatures.  And, you can produce bleaching
that doesn't lead to coral mortality.  They are two different processes.
      For the big picture, the gold prize of saving the world's coral reef
ecosystems, I think coral mortality is vastly more important than
bleaching.  Bleached corals don't have to die, if it isn't too hot they can
survive, recover and go on to reproduce a few years later.  Bleaching is a
warning sign that corals are stressed and close to the mortality
threshold.  But when coral colonies die, for them the game is up and death
is permanent, and for the coral reef ecosystem, that takes a lot longer to
recover from, and recovery is more uncertain, since there might be a phase
shift away from coral to something like algae, and the system could get
stuck in a non-coral state and not return in the foreseeable future.  But
I'm not saying that bleaching is harmless or we should it ignore it, quite
the contrary.
       There are people who say we are going to have to learn to live with
changed ecosystems.  That may be true.  But I don't think living with algae
beds or coral rubble fields that replace coral reef ecosystems is going to
be any picnic.  Perhaps my biggest worry is that as far as I know,
macroalgae beds don't produce very many fish.  And my observations suggest
that coral rubble beds produce precious few fish.  There are several
hundred million people in low-income countries, living along reef
shorelines that absolutely depend on coral reef fish for food and
survival.  I've seen estimates in the 200-500 million people range, if I
remember.  Those people will be in dire straights if most of the corals get
killed by global warming.
     By the way, I have yet to see an explanation of how selectively
breeding temperature resistant corals, whether in captivity or ocean coral
farms, is going to save the world's corals.  There is a no so small matter
of how do you scale up from a few hundreds or thousands of colonies to not
just billions, probably way more than trillions of colonies on reefs.  Same
applies to anyone who figures out a way to get corals not to bleach.  That
doesn't mean we should abandon those projects.  But we need to be realistic
and not put all our eggs into that basket, because the chances we'll find
some miraculous way of planting out 10 to the 15th power corals on the vast
area of the world's coral reefs isn't very high.  It is, actually, treating
the symptoms, not the cause of the disease.  "An ounce of prevention is
worth a pound of cure."  If we want to solve the problem, we HAVE to
minimize global warming.  No other way around it.  There was a Palumbi
group article that found that if we warmed on one of the lower pathways,
corals could adapt, but on the higher or even medium pathways, they can't.
There is a physiological limit to how far and fast corals can evolve
temperature tolerance.  Once the oceans reach that limit, from there on,
selection and assisted evolution and natural evolution will not save
corals.  Will not, and then if we put all our eggs in that basket, we lose
the game, we lose the coral reef ecocsystems, lose the prize, the gold,
lose completely and utterly and 10's of millions of human lives will be at
risk as a result.
      We HAVE to get global warming under control, not just for reefs, but
to keep parts of the world at habitable temperatures for humans.  It is in
our own best self interest.
       Cheers,  Doug

On Mon, Mar 30, 2020 at 3:13 AM Scott Wooldridge via Coral-List <
coral-list at coral.aoml.noaa.gov> wrote:

> Hi Steve,
> As you may have picked up, I was extending my comments to their
> thought-provoking extremes. Obviously, many scientists are doing innovative
> work on trying to better understand the inner working of the coral
> bleaching process. Indeed, I read a great summary report in a recent issue
> of PNAS, which is well worth a read.
> https://www.pnas.org/content/117/5/2232.short
> You are also correct that many scientists, managers and policy makers have
> been striving to improve reef water quality as an important conservation
> measure.
> What I will say, however, is that what I am advocating is not the idea that
> poor water quality is just one (of many) additive stresses that impact on
> coral reefs, i.e. a contributing straw that helps breaks the camel’s back.
> Instead, I envisage inorganic nutrient enrichment as an intrinsic,
> co-determining driver of thermal coral bleaching. That is, excess nutrient
> enrichment increases the likelihood of coral bleaching (per unit thermal
> anomaly).  To understand this better, and how it interacts with our efforts
> to reduce future rates of global warming, check out:
> https://www.researchgate.net/publication/235762816_Safeguarding_coastal_coral_communities_on_the_central_Great_Barrier_Reef_Australia_against_climate_change_Realizable_local_and_global_actions
> Abstract
> The threats of wide-scale coral bleaching and reef demise associated with
> anthropogenic (global) climate change are widely known. Less well
> considered is the contributing role of conditions local to the reef, in
> particular reef water quality, in co-determining the physiological
> tolerance of corals to increasing sea temperatures and declining pH. Here,
> the modelled benefit of reduced exposure to dissolved inorganic nitrogen
> (DIN) in terrestrial runoff, which raises the thermal tolerance of coastal
> coral communities on the central Great Barrier Reef (Australia), is
> considered alongside alternative future warming scenarios. The simulations
> highlight that an 80% reduction in DIN ‘buys’ an additional ~50–60 years of
> reef-building capacity for No Mitigation (‘business-as-usual’) bleaching
> projections. Moreover, the integrated management benefits provided by: (i)
> local reductions of ~50% in DIN contained in river loads, and (ii) global
> stabilisation of atmospheric CO2 below 450 ppm can help ensure the
> persistence of hard-coral-dominated reefscapes beyond 2100. The simulations
> reinforce the message that beyond the global imperative to mitigate future
> atmospheric CO2 emissions there still remains the need for effective local
> management actions that enhance the resistance and resilience of coral reef
> communities to the impacts of climate change.
> I hope this clears up some misconceptions, and assures people that beyond
> water quality improvements I DO also advocate strongly of the importance of
> reducing our carbon footprints.
> But the central tenet of my previous post remains. We need to keep pressing
> for a more comprehensive understanding of the coral bleaching mechanism. It
> is not perfectly understood. Lots still remains to be discovered. And we
> should be excited by the challenges that presents, and the hope that
> remains for finding solutions to help save coral reefs from extinction.
> For your consideration,
> Scott
> >
> > Message: 3
> > Date: Wed, 25 Mar 2020 16:26:46 -0400
> > From: sealab at earthlink.net
> > To: Scott Wooldridge via Coral-List <coral-list at coral.aoml.noaa.gov>
> > Cc: coral list <coral-list at coral.aoml.noaa.gov>
> > Subject: Re: [Coral-List] So you think you understand coral bleaching?
> > Message-ID: <31dd1334-25d8-4ffa-9193-bcdf8e2774c4 at Steves-iPad>
> > Content-Type: text/plain; charset="utf-8"
> >
> >
> >
> > Hi Scott,
> >
> > Your ideas certainly raise some interesting points. I agree that the reef
> > science community here can sometimes get bogged down discussing how to
> > minimize our carbon footprints, but I was struck most by your assertion
> > that instead, finding a CURE for bleaching should consume ?99.9% of the
> > best thinking time? of coral reef scientists. As I view it, coral
> > scientists are in no way resigned to the belief that reducing global
> carbon
> > emissions is the ?sole solution?. If anything, there are already great
> > efforts being made to divert attention away from the need to address
> > climate change and towards an efficacy favoring restoration involving
> some
> > form of enhanced resistance. These projects may not be based on the FRONT
> > END of the bleaching response as you described, but they are focused on
> > similar goals. In addition, if the favorable symbiotic conditions you
> seek
> > are dependent on ?ensuring a severe limitation of the seawater supply of
> > nutrients? - haven?t we been striving for this all along?
> >  It sounds to me like the venerable call for improvements in water
> quality
> > that many have been advocating for years. Let?s just imagine that the
> > supply of nutrients was miraculously brought under control and water
> > quality was restored. With that elusive goal achieved, wouldn?t it be
> > better to work to reduce carbon emissions and then let nature take its
> > course? Why would we want to turn our backs on trying to solve the
> > existential problem that is climate change with all of its implications
> for
> > both marine and terrestrial ecosystems in search of a highly improbable
> > ?cure? or coral bleaching? What could be better than envisioning a
> scenario
> > whereby we effectively address climate change AND restore water quality
> > thereby reducing widespread bleaching and outbreaks of coral diseases all
> > in one fell swoop? That?s what I would call going for the gold! If our
> > current crisis with COVID-19 teaches us anything, it should serve as
> > testimony to the connectivity and fragility of life on this planet
> >  . A lesson that we would all do well to apply to climate change and the
> > many challenges it presents to us all.
> >
> > Regards,
> >
> > Steve
> >
> > Sent from EarthLink Mobile mail
> >
> > nd of Coral-List Digest, Vol 139, Issue 19
> > *******************************************
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Douglas Fenner
Lynker Technologies, LLC, Contractor
NOAA Fisheries Service
Pacific Islands Regional Office
PO Box 7390
Pago Pago, American Samoa 96799  USA

"Already, more people die  <http://www.nws.noaa.gov/om/hazstats.shtml>from
heat-related causes in the U.S. than from all other extreme weather events."


Even 50-year old climate models correctly predicted global warmng

"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

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