[Coral-List] Getting creative about coral bleaching?

[Austin Bowden-Kerby]

Hi Katy,

Very good questions, but you won't likely find this in the literature. I
will share what I know and my suggestions from personal experience below.
What you and all coral reef people in Florida and much of the Caribbean are
facing must be horrific, but the days of sitting by and watching should not
continue.

I think that it is too late to consider nutrients or other such
interventions widely, but it might be a good time for experimentation.
Here in Fiji, I ran an experiment in 2019 using iron chelate, manganese
chelate, and phosphate, as the literature suggested that these nutrients
might help reinforce the symbionts and prevent bleaching.  I collected
coral fragments from cooler reefs and brought them inshore to warmer reefs
during a moderate bleaching event.  I treated the corals by soaking in the
respective solutions for just an hour.  The results were inconclusive,
likely due to our already nutrient enriched waters, but Mn did seem to
help.  I think for the oligotrophic waters of oceanic atolls that nutrient
treatment might be much more effective.

But I think all those doing restoration might consider direct interventions
like shading.  We have collected coral fragments during a bleaching event
and put them under shade in the nursery. They did very well despite the hot
water and the fact that they changed their orientation on the rope
nursery.  During the summer months, UV stress adds to any heat stress
during transplantation.  Shading is able to prevent bleaching on the
up-facing sides of the fragments during the hot summer months, and this
includes during bleaching events.  With shading, it is possible to gather
bits of all the coral genotypes as a bleaching approaches or even during a
bleaching, to help ensure that you do not lose the genotypes.  Shading is a
fairly straightforward process for the rope nurseries suspended from metal
bar tables hammered into the substratum.  We use two iron rods, each sewn
into the ends of nursery shade cloth 50% shade, and draped over the
sections. We scrub the shade cloth once a week.

For those using the floating tree nurseries, you might consider the option
of lowering the nurseries deeper, or moving the nurseries to deeper water,
or perhaps creating new multiple genotype nurseries, and moving those into
cooler or deeper waters during this heat stress, so that you don't lose
your genotypes?  If you are going to try something, the sooner the better!

We have also collected bleaching resistant corals during the recent
bleaching event, on the back side of the bleaching, when the waters had
already begun to cool.  The bleached corals take many weeks to recover, and
so you have a month or so to identify and collect those which did not
bleach.  This past April, I worked with the indigenous youth of Moturiki
Island to create a nursery of bleaching resistant corals. The mass
bleaching was very bad in the East of Fiji and resulted in about 99%
bleaching of the Acropora corals and about 30% mortality in our site.  The
community required bleaching resistant corals to work with, to enhance
their no-take Tabu areas, and we realized that within a month or so, the
expansive masses of partially bleached corals would mostly recover,
obscuring the bleaching resistant ones.  The youth were trained to
differentiate between bleached, recently dead, and unbleached corals, and
then we all fanned out on the reef to find and collect the few unbleached
Acropora corals (within 200-300 meters). These few bleaching resistant
corals, collected as intact whole colonies, were put onto a table nursery,
unshaded.  This was undoubtedly a bit of a stress, but they did not bleach
in the UV, as we maintained the colonies in their original upright
position.

Perhaps the most important intervention is after the bleaching subsides.
If you have had a lot of coral mortality, the predator to prey ratio of
coral predators to their favorite coral species will be skewed.  This has a
very negative impact, as these predators will kill off some or all of your
bleaching-resistant survivors, and this will prevent natural adaptation
processes from occurring.  So it is vital to closely monitor anything rare
post-bleaching, and to conduct predator removal activities.  Sometimes
parrotfish and butterflyfish can wipe out the few remaining corals,
especially the Acropora. Badly bitten corlas require a rapid
intervention.  Rope and floating nurseries provide a refuge from parrotfish
predation, while fixed nurseries do not, unless they are located off the
reef in the sand, too far for the fish to cross. The down-side is that
without the reef fish to clean the nursery, you will have to do regular
cleaning.  The floating nurseries would also be ideal for isolation from
predators, but if the UV levels are high, how might you shade them?
Perhaps locate them in deeper water until the UV levels decline?

Over here in Fiji, working with corals only requires permission from
the village chiefs, and there is no government permitting system for coral
work. Florida and the Caribbean is a very different situation, and I am not
advocating that people be set loose on the reef - be careful to work within
your permits!

Coral restoration is quickly becoming endangered and threatened species
conservation.  When the firestorm approaches, foresters stop planting trees
and focus their efforts on quickly protecting precious genetic material
from the flames.

Please do what you can, as the future of coral reefs depends on each and
every species of coral surviving, until humanity finally finds
our balance!

Regards,

Austin


Austin Bowden-Kerby, PhD
Corals for Conservation
P.O. Box 4649 Samabula, Fiji Islands
https://www.corals4conservation.org
Publication on C4C's coral-focused climate change adaptation strategies:
https://www.mdpi.com/2673-1924/4/1/2/pdf
Film on our "Reefs of Hope" coral restoration for climate change adaptation
strategies:  https://www.youtube.com/watch?v=BG0lqKciXAA
TEDx talk https://www.youtube.com/watch?v=7PRLJ8zDm0U
https://www.globalgiving.org/projects/emergency-response-to-massive-coral-bleaching/
<https://www.globalgiving.org/projects/emergency-response-to-massive-coral-bleaching/>







On Fri, Jul 21, 2023 at 12:59 AM Cummings, Katy via Coral-List <
coral-list at coral.aoml.noaa.gov> wrote:

> We do a great job of monitoring (dying) corals, but has anyone tried
> drastic measures to save bleaching corals? Sunshades over certain colonies?
> Supplemental feeding? Booms over reefs to trap sargassum and shade them?
> Giant ice cubes in the ocean à la Futurama (just kidding)? Surely there is
> something we can do, if we can feed manatees almost half a million pounds
> of romaine lettuce to keep them alive after mass seagrass mortality.
>
> I see a few papers on shading, manganese enrichment, and antioxidants but
> don't know of anything that has been put to practice in the wild on wider
> scales. Does anybody know of any real-word examples?
>
> Katy Cummings
> Coral Program Outreach Coordinator
> Coral Research Program
> Fish & Wildlife Research Institute
> Florida Fish and Wildlife Conservation Commission
> 2796 Overseas Hwy Suite 119 | Marathon, FL 33050
> Katy.Cummings at MyFWC.com<mailto:Katy.Cummings at MyFWC.com> |
> https://myfwc.com/research/habitat/coral/
> Phone:  262-352-7232
>
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