[Coral-List] New paper on the dispersal (or lack of) of coral larvae across the East Pacific Barrier

Wed Oct 12 07:14:54 EDT 2016

Dear Hector and Dennis, many thanks for your interest and comments. I am
replying to both your emails at the same time as I think they relate to the
same issue.

Hector, I'm sorry that you feel we have "overlooked the work of so many
people" in this paper, but this seems to be a misunderstanding of the focus
of the paper. Of course, taxonomy, biogeography and genetics are critical
in answering this longer term question of how eastern Pacific corals came
to be there in the first place*.

Instead, however, in our study we examined dispersal over recent time
scales (1997-2011) only, with the aim of determining whether larval
dispersal from the central Pacific may have aided the recovery of eastern
Pacific coral populations following the 1997-98 El Niño. We looked at
dispersal over a range of ENSO conditions, including La Niña and neutral
conditions, and found no eastward connections at any time over the period
modelled.

We cannot rule out that eastward connections may not have been made over
previous (say the 1982-83 El Niño or further back) or more recent events.
In fact, one of the main findings of the study is that modelled larvae did
come close to making connections from the west to east in 1997, but subtle
details of the surface circulation meant that such connections were
'narrowly' missed.

Regarding the "hundreds of Indo Pacific species that live... in the coast
of the Americas" - I would like to clarify that we only modelled broadcast
spawning coral larvae in this study (of which only a small number of
Indo-Pacific species are found in the eastern Pacific). For other species,
such as fish, whose larvae may travel deeper in the water column or have
different swimming capabilities, the results may well have been very
different.

Kind regards,
Sally

*Regarding this question, this recent genetics paper Micheal Hellberg et
al. may be more appropriate - it discusses the timing and direction of
first colonisation of *Porites *sp into the eastern Pacific, suggesting
initial colonisation was west to east: Hellberg, M. E., Prada, C., Tan, M.
H., Forsman, Z. H. and Baums, I. B. (2016), Getting a grip at the edge:
recolonization and introgression in eastern Pacific *Porites *corals. J.
Biogeogr.. doi:10.1111/jbi.12792.

*Dr Sally Wood  *

School of Earth Sciences, University of Bristol
Wills Memorial Building, Queens Road, BRISTOL BS8 1RJ
+44 (0)117 954 5429 | w: salwood.weebly.com | t: @SalWood82
<https://twitter.com/SalWood82>

On 7 October 2016 at 17:21, Héctor Reyes Bonilla <hreyes at uabcs.mx> wrote:

> The paper is great, but I have a simple question (that I discussed
> with Iliana, Peter Glynn and others in the last ICRS). How the
> mechanism explain the hundreds of Indo Pacific species that live happy
> and healthy in the coast of the Americas, while less than a dozen have
> moved in the opposite direction? El Niño can explain one part of the
> facts, but the other half? The anti-El Niño? (sadly called "La NIña",
> which makes no sense in Spanish).
>
> Just a remainder: taxonomy and old fashioned biogeography still
> counts, and have to be considered and improved with the excellent new
> tools and perspectives of the researchers. To overlook the work of so
> many people from the XIX and XX Century is not a good policy.
>
> Hector Reyes
>
> 2016-10-05 11:57 GMT-06:00 Dennis Hubbard <dennis.hubbard at oberlin.edu>:
> > A very interesting paper. My simplistic understanding of this previously
> > was that the Isthmus of Panama created a barrier between Caribbean and
> > Pacific regions and that larval flow was dominantly (perhaps solely) from
> > east-to-west in the Trade Winds. This would seem to be consistent with
> > these new findings. I was not aware that there was a lot of thought of
> > westward flow into this area, although the eastward flow of larvae from
> the
> > Tuamotus to Easter Island seems reasonably well documented.
> >
> > Might there be any value in looking at the development of the species of
> > interest following the closure of the Isthmus of Panama to see whether
> > those furthest east (which, if my recollection of the literature is
> > correct, were the first to be impacted - Peter Glynn's papers) might have
> > been the original sources of larvae to the west way back when? If so,
> might
> > this infer that recent events are "unprecedented" over the past 2 million
> > years?
> > Dennis
> >
> > On Wed, Oct 5, 2016 at 5:55 AM, Sally Wood <Sally.Wood at bristol.ac.uk>
> wrote:
> >
> >> A bit late but some of you might be interested in a new paper published
> in
> >> Nature Communications in August, which revisits the theory that El Niño
> >> events may promote long distance dispersal across the East Pacific
> Barrier:
> >>
> >> El Niño and coral larval dispersal across the Eastern Pacific marine
> >> Barrier
> >> <http://www.nature.com/articles/ncomms12571>, Wood, S., Baums, I.B.,
> >> Paris,
> >> C.B., Ridgwell, A., Kessler, W.S., Hendy, E.J., Nature Communications
> >> 7:12571 (2016).
> >>
> >> The study, which compares a modelling approach with genetic data across
> the
> >> Pacific, is a collaboration between the University of Bristol's Coral
> Reef
> >> research group, the Paris laboratory at RSMAS and the Baums laboratory
> at
> >> Penn State, with input from oceanographer Billy Kessler at NOAA's
> Pacific
> >> Marine Environmental Laboratory and climatologist Andy Ridgwell at the
> >> University of California at Riverside.
> >>
> >> The press release (printed below) can be viewed here
> >> <http://www.bris.ac.uk/news/2016/august/reef-castaways.html>, and the
> full
> >> paper obtained here <http://www.nature.com/articles/ncomms12571>. An
> >> animation of example modelled dispersal paths by month of release can be
> >> viewed here <https://www.youtube.com/watch?v=mMzuPcBTq5c>.
> >>
> >>
> >> *---------- U. Bristol press release 23rd Aug 2016 -----------*
> >>
> >> *Reef castaways: Can coral make it across Darwin’s ‘impassable’
> barrier?*
> >>
> >>
> >>
> >> An international team of researchers have shown that vulnerable coral
> >> populations in the eastern tropical Pacific have been completely
> isolated
> >> from the rest of the Pacific Ocean for at least the past two decades.
> >>
> >>
> >>
> >> Ocean currents can change speed and even direction depending on the
> season
> >> or climatic events like El Niño.
> >>
> >>
> >>
> >> The new study led by University of Bristol researchers has used a
> >> state-of-the-art computer model to trace the journeys of coral larvae
> >> transported at the whim of these currents.
> >>
> >>
> >>
> >> The international team discovered that even during the record-breaking
> El
> >> Niño of 1998, coral larvae could not survive long enough to make the
> 5,000
> >> km trip from reefs in the central Pacific to those in the east.
> >>
> >>
> >>
> >> These findings support the opinion of Charles Darwin, who considered
> this
> >> intimidating expanse of open ocean ‘impassable’ - countering recent
> >> arguments that the ‘East Pacific Barrier’ must be breachable since the
> same
> >> coral species are found on both sides. If so, the study argues, such
> >> breaches have not occurred recently.
> >>
> >>
> >>
> >> Dr Sally Wood
> >> <http://www.bristol.ac.uk/earthsciences/people/person/
> >> sally-wood/overview.html>,
> >> from the Coral Reef Research at Bristol
> >> <http://www.bristol.ac.uk/biology/research/ecological/coral/> (CRAB)
> group
> >> in the School of Earth Sciences <http://www.bristol.ac.uk/
> earthsciences/>
> >> and lead author of the paper, explains: “Coral build the framework of
> >> tropical coral reefs, creating habitats which support one of the most
> >> diverse ecosystems on Earth.
> >>
> >>
> >>
> >> “Whether coral reefs can survive the pressure of climate change as well
> as
> >> local stresses will depend to a large extent on the ability of coral to
> >> reproduce and disperse; to replenish damaged populations, migrate from
> >> deteriorating conditions and colonise new frontiers. So it’s important
> to
> >> map where coral are able to get to.”
> >>
> >>
> >>
> >> Dr Erica Hendy
> >> <http://www.bristol.ac.uk/earthsciences/people/person/
> >> erica-hendy/overview.html>,
> >> Lecturer in Biogeochemical Cycles in the School of Earth Sciences,
> added:
> >> “However, you simply can’t tag a coral larvae to follow where it ends
> up as
> >> you would a large marine animal like a turtle or shark. Coral larvae are
> >> smaller than a poppy seed, soft-bodied and released in overwhelming
> >> numbers.
> >>
> >>
> >>
> >> “When swept off their home reef, they have an infinitesimally small
> chance
> >> of ever reaching a suitable place to settle and become a coral colony.
> We
> >> therefore use computer simulations to answer these critical questions
> about
> >> coral biology and conservation.”
> >>
> >>
> >>
> >> The study tracked the journeys of over five billion model ‘larvae’ from
> 636
> >> remote reefs scattered across the central and eastern Pacific Ocean
> over a
> >> 14 and a half year period. Using the state-of-the-art Connectivity
> Modeling
> >> System <https://github.com/beatrixparis/connectivity-modeling-system>,
> >> developed by Claire Paris
> >> <https://www.rsmas.miami.edu/people/faculty-index/?p=
> claire-paris-limouzy
> >> >,
> >> associate professor of ocean sciences at the University of Miami’s
> >> Rosenstiel
> >> School of Marine and Atmospheric Science
> >> <https://www.rsmas.miami.edu/people/faculty-index/?p=
> claire-paris-limouzy>
> >> and run on the University of Bristol’s BlueCrystal supercomputer
> >> <https://www.acrc.bris.ac.uk/>, the researchers could manage the
> massive
> >> computational demands of modelling such large numbers.
> >>
> >>
> >>
> >> This allowed the team to test, for the first time, a long-standing
> theory
> >> that countered Darwin - that El Niño events promote long-distance
> dispersal
> >> of coral larvae across the Pacific Ocean.
> >>
> >>
> >>
> >> The results showed that the eastern Pacific corals (from Baja
> California in
> >> the north to the coastline of Ecuador and the Galapagos Islands in the
> >> south) have been completely cut off from the rest of the Pacific since
> at
> >> least the 1998 El Niño.
> >>
> >>
> >>
> >> As is happening worldwide at the moment, this extreme El Niño wiped out
> >> many of the corals in the eastern Pacific.
> >>
> >>
> >>
> >> Coral populations recover from such stress events through the
> proliferation
> >> of survivors and colonisation by new recruits from neighbouring
> >> less-impacted reefs. However, the more isolated a reef, the more
> >> self-reliant, and the higher the likelihood of local extinctions.
> >>
> >>
> >>
> >> The study’s findings provide evidence that local conservation is
> essential
> >> for the sparse and poorly-protected, but economically and
> >> environmentally-important coral reefs of the eastern Pacific Ocean.
> >>
> >>
> >>
> >> Dr Wood concluded: “Our results demonstrate that it is even more
> important
> >> to conserve the genetic diversity of the remote reefs in this
> >> environmentally hostile part of the Pacific.
> >>
> >>
> >>
> >> “They’re on their own out there, so whatever we can do to protect them
> >> locally really will have an impact.”
> >>
> >> *Dr Sally Wood  *
> >>
> >> School of Earth Sciences, University of Bristol
> >> Wills Memorial Building, Queens Road, BRISTOL BS8 1RJ
> >> +44 (0)117 954 5429 | w: salwood.weebly.com | t: @SalWood82
> >> <https://twitter.com/SalWood82>
> >> _______________________________________________
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> >> Coral-List at coral.aoml.noaa.gov
> >> http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
> >
> >
> >
> >
> > --
> > Dennis Hubbard
> > Chair, Dept of Geology-Oberlin College Oberlin OH 44074
> > (440) 775-8346
> >
> > * "When you get on the wrong train.... every stop is the wrong stop"*
> >  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
> > _______________________________________________
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> > Coral-List at coral.aoml.noaa.gov
> > http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
>
>
>
> --
> Héctor Reyes Bonilla
> Departamento Académico de Ciencias Marinas y Costeras
> Universidad Autónoma de Baja California Sur
> Carretera al sur km 5.5. Col. El Mezquitito
> La Paz, B.C.S., C.P. 23080.
> Tel. (52-612) 123-8800, ext. 4814
> Fax (52-612) 123-8819.
>