[Coral-List] New Paper: Resilient corals in the Phoenix Islands

Wed Sep 29 04:01:42 UTC 2021

I much appreciate the perspective Austin is giving us.
    I am reminded that several decades ago, someone, I have a feeling it
might have been Terry Done, pointed out that any reef that had widespread
mortality including of the giant colonies like massive Porites, can recover
coral cover and superficially appear recovered, yet the death of
multi-century old giant corals means that the reef will not recover its
species composition within even many generations of humans (during which a
lot of what we consider normal modern society may become unrecognizable).
I have been frequently reminded by others that coral cover is only a first,
quick and dirty measure, of what the benthic community is like.  There is
much, much more and it is important.  Austin is exactly right, the Acropora
are some of the best species for providing habitat for a wide variety of
fauna, fish, inverts, etc, which disappear immediately upon the death of
its host in most cases (because they died).
      I think Austin has a very important point here.  Acropora is by far
the largest genus of corals, with an amazing diversity of colony shapes,
and it has often been pointed out that many of the world's reefs were/are
dominated by the genus, in both living cover and diversity.  Yes, they are
often (but not always?) weedy, fast growing species, also they are among
some of the most affected by disturbances like bleaching, disease,
hurricanes, crown-of-thorns, etc.  So you can lose loads of them fast, but
they may be able to grow back fast.
       If we think that billions of colonies in a species makes that
species immune to extinction, as a recent paper argued, I beg to differ.
Check out the "passenger pigeon" in North America.  Estimated to have had a
population in the billions.  Humans with guns exterminated that species.
       That paper was based on sampling, as is almost all science.  But as
far as I could tell, there was no mention of the obvious fact that the
sampling was (unintentionally and unavoidably) highly biased.  The sampling
was done by transects.  A massive and admirable study.  BUT, they found in
their big sampling effort, about half of all the coral species known in the
Indo-Pacific, perhaps a tad less.  Was it a random sample of all the coral
species in the Indo-Pacific???  No way.  Such sampling favors the more
common and widespread species.  It will miss endemic species.  It will miss
all species that live only at depths that are different from where the
transects are.  The species missed will be highly enriched in species that
are rarer than those reported, which will be highly enriched in the most
abundant species.  So it presents a highly distorted view of the
Indo-Pacific coral diversity, and all the talk about billions of colonies
applies to the abundant species in their samples, but does NOT apply to the
rare species.  Ever heard the phrase that in highly diverse ecosystems most
species are rare???
      So why be concerned about rare species??  They're expendable,
right??  Sure, if you don't care about the diversity of organisms that we
humans are abusing, and you don't care about whether they survive and
whether the diversity survives.
      Which brings me back to the problem of losing species.  The kind of
thing that's been going on in the equatorial parts of of Kiribati and may
well be a window into the future of world coral reefs, strikes not at half
a dozen species of giant Porites corals (fantastic as they are), but at the
heart of diverse coral reefs, the most diverse coral genus, Acropora, which
I would argue we don't even know adequately yet.
      I like to point out that coral reefs probably would recover fine if
we humans stopped abusing them.  But I hasten to add that recovery is
possible ONLY if the component species of the reefs have not gone extinct.
The reason extinction is important is that it is permanent.  That's what
spurs concerns and efforts.  For more perspective on the dangers of
extinction for rare species, particularly sessile species like corals that
can't go out finding their rare conspecifics to mate with, I recommend
reading up on Allee Effects, there is an abundant literature.  Once some
species get below a certain number of individuals, their populations may
enter positive feedback cycles that cause the population to crash and
extinction to occur.  For coral reef organisms, I recommend Birkeland et al
(2013).  These effects are strongest for species that are the rarest;
species that are not rare have mechanisms that provide population
stability, though the pigeon example shows that there is no absolute
protection for any species, no matter how abundant.
      The thin edge of the wedge is already here, several coral species
have gone regionally extinct in recent years, and one, (Ctenella chagius)
is very close to the precipice of global extinction (Sheppard et al, 2020
and references therein).  No, it is not a huge crisis yet, but if these
equatorial reefs are losing almost all their Acropora, and this is a
harbinger of what is coming for the world reefs, the alarm bells are
ringing.  From far off it may seem.  But how much diversity was lost on the
northern and southern Great Barrier Reef when there was huge mortality that
drove live cover to low levels, and yes live cover recovered if we are not
to dismiss the monitoring results of the Australian Institute of Marine
Science monitoring program??  Check the graphs for coral cover of each of
the 3 sections over time, they are really quite astounding:
https://www.aims.gov.au/reef-monitoring/gbr-condition-summary-2020-2021
If you lose 90% of the cover, how many rare species were just pushed to
regional extinction?  If 99% loss, how many?  Regional extinctions are a
step towards global extinctions.  Do we KNOW for a fact that there are no
species endemic to that region that were driven to global extinction???  I
don't think we do.  Zoe Richards (2018) wrote a paper asking if we knew
whether there were any "silent" (unrecorded) extinctions on the Great
Barrier Reef.  If I remember, the answer was we don't know, there are too
many species and we don't monitor but a tiny tiny fraction of the
diversity.  Unfortunately it seems like we aren't really trying very hard
even to sample.  Among other things, we need to monitor the abundance and
trends of individual coral species, like we do fish.
     So, I don't recommend complacency in this issue, and I thank Austin
for his perspective.
      But of course, we need to attack the primary cause of all this.  For
that I recommend an article that points out that NONE of the leading
economic power countries on the planet are in line with the Paris
Agreement.
https://edition.cnn.com/2021/09/15/world/climate-pledges-insufficient-cat-intl/index.html

     Cheers, Doug

Birkeland, C., M. W. Miller, G. A. Piniak, C. M. Eakin, M. Weijerman, P.
McElhany, M. Dunlap,

       and R. E. Brainard. Safety in numbers? Abundance may not safeguard
corals from increasing carbon dioxide. BioScience 63: 967-974.

Sheppard, C., A. Sheppard, and D. Fenner. 2020. Coral mass mortalities in
the Chagos Archipelago over 40 years: Regional species and assemblage
extinctions and indications of positive feedbacks. Marine Pollution
Bulletin 154: 111075

Richards, Z. T., Day, J. C. 2018.  Biodiversity of the Great Barrier Reef-
how adequately is it protected?  PeerJ   https://peerj.com/articles/4747/

On Thu, Sep 16, 2021 at 2:43 PM Austin Bowden-Kerby via Coral-List <
coral-list at coral.aoml.noaa.gov> wrote:

> Thanks for that David,
>
> I agree with you, as far as on geological timescales.  But for Kiribati, on
> the leading edge of the global coral reef collapse, unfortunately the
> oceanic reefs are doing as bad or worse than the lagoons. The ocean facing
> reefs are adapted to cooler waters so they kick the bucket as badly as the
> lagoonal corals when mass bleaching temperatures arrive and where they can
> linger for over half the year.  For the Gilbert chain, bleaching
> temperatures dominated for 30 months out of 60 since 2014, until La Nina
> conditions finally arrived last year, giving them a one or two year break.
>
> The thermal stress is superimposed on both ocean and lagoon habitats, and
> corals tend to adapt to near the upper thresholds for their symbionts.  So
> all corals, of both lagoon and ocean reefs, are equally stressed and in
> danger of being wiped out.  I conjecture that the most resilient
> coral populations will be found at the transition between lagoon and
> oceanic conditions- the reef passes.  If this hypothesis is correct, then
> those reef pass areas are where our conservation efforts might best be
> focused.
>
> The lessons of Kiribati have taught us a lesson for Fiji and Tuvalu and
> Samoa, where it is still not too late.  Our strategy in recent years is to
> locate and move corals of the same species as those on the ocean facing
> reefs- from the warm lagoons, nearshore reef flats, and hot pockets, out to
> the cooler outer lagoon and pass areas where we establish them in gene bank
> nurseries. The goal is to create patches of these resistant corals on the
> ocean reefs themselves, where they stand a much better chance into the
> future, and where they can then begin to spread their resilience.
>
> Mother Earth has a fever, but she has a strategy of Her own to protect the
> coral reefs- sea level rise.  Imagine the positive impact that adding one
> or two meters of water will have on the shallow coral reefs globally.
> Vastly more area for corals to grow, increased upward scope for growth, and
> a cooling of the lagoons and shallows. Of course the coastal areas and
> human populations may not fare so well.  But seriously, we
> deserve every millimeter!
>
> Regards to all,
>
> Austin
> .
> Austin Bowden-Kerby, PhD
> Corals for Conservation
> P.O. Box 4649 Samabula, Fiji Islands
> https://www.corals4conservation.org
>
> https://www.globalgiving.org/projects/emergency-response-to-massive-coral-bleaching/
> <
> https://www.globalgiving.org/projects/emergency-response-to-massive-coral-bleaching/
> >
>
>
> Teitei Livelihoods Centre
> Km 20 Sigatoka Valley Road, Fiji Islands
> (679) 938-6437
> http:/www.
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> http://permacultureglobal.com/projects/1759-sustainable-environmental-livelihoods-farm-Fiji
> >
> teiteifiji.org
>
> http://permacultureglobal.com/projects/1759-sustainable-environmental-livelihoods-farm-Fiji
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>
>
> On Thu, Sep 16, 2021 at 6:29 AM David Blakeway via Coral-List <
> coral-list at coral.aoml.noaa.gov> wrote:
>
> > In assessing these reefs I think it's worth considering where they're at
> in
> > terms of their natural life cycle. Kiribati, for example, looks pretty
> > terminal to me. You could imagine that 1000 years ago it might have
> > resembled Tabueran (3.86, -159.32) and 1000 years from now it might look
> > like Washington Island (4.68, -160.38). That process (losing all lagoon
> > corals) is completely natural. And probably wouldn't be a gradual
> > incremental process (on our timescale); more likely the lagoon coral
> > community would undergo massive fluctuations in the terminal stage, while
> > heading toward long-term senescence. I agree that preserving Kiribati
> > corals is critical insurance. My point is just that--for reefs in
> > general--we shouldn't expect good stable coral cover and diversity in
> > late-stage reefs approaching sea level.
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