[Coral-List] Parrotfish loss drives reef decline

Pawlik, Joseph pawlikj at uncw.edu
Fri Feb 17 07:15:57 EST 2017

Hi all,

Dr. Kuffner's perspective paper makes some interesting points about "wimpy" corals and Caribbean reef resilience.  Branching Acropora spp. certainly took a hit from disease in the 1980s and haven't recovered, but some important reef-building species (Orbicella, Montastrea) seemed to fade more gradually, with ever decreasing growth rates.

We've proposed the "vicious circle" hypothesis for why this might be happening -- a feedback loop between sponges and seaweeds. Seaweeds quickly took over free space after the double-whammy of coral and Diadema die-offs, with slower-growing sponges taking years longer to recruit and hold space.  Seaweeds exude labile dissolved organic carbon (DOC) which is a food source for sponges, and sponges pump-out nutrients that fertilize the seaweeds. This loop not only benefits sponges and seaweeds, but also seawater microbes, which may alter the microbiome of corals in negative ways.
Sponge cover on Caribbean reefs is now about the same as coral cover, but sponge biomass is likely orders of magnitude greater.  Sponges turn-over a substantial portion of the the water column above the reef on a daily basis. Further, the sponge fauna of the Caribbean is strikingly different from that found on most Indo-Pacific reefs (dominated by foliose phototrophic species), suggesting that Caribbean sponges adapted to a different nutritional environment, where DOC from seaweeds or terrestrial sources is more available. We speculate that the continued success of octocorals (sea fans and whips) on Caribbean reefs may be similarly explained, given their high surface area and upright growth into the water column.
Our group has seen a 122% increase in giant barrel sponges on reefs in the Florida Keys, with a 40% increase in sponge biomass for 2000-2012, and these increases are evident on reefs across the Caribbean. If these demographic trends continue, the "vicious circle" may turn many Caribbean coral reefs into sponge reefs.

Pawlik, J.R., Burkepile, D.E., Vega Thurber, R. 2016.<http://people.uncw.edu/pawlikj/2016BioSciencePawlik.pdf> A vicious circle? Altered carbon and nutrient cycling may explain the low resilience of Caribbean coral reefs. BioScience, 66: 470-476


McMurray, S.E., Finelli, C.M. and Pawlik, J.R. 2015.<http://people.uncw.edu/pawlikj/2015JEMBEMcMurray.pdf> Population dynamics of giant barrel sponges on Florida coral reefs. Journal of Experimental Marine Biology and Ecology, 473: 73-80
McMurray, S.E., Johnson, Z.I., Hunt, D.E., Pawlik, J.R., Finelli, C.M. 2016..<http://people.uncw.edu/pawlikj/2016McMurrayLO.pdf> Selective feeding by the giant barrel sponge enhances foraging efficiency. Limnology and Oceanography, 61: 1271-1286
Loh, T.-L., McMurray, S.E., Henkel, T.P., Vicente, J. and Pawlik, J.R. 2015<https://dx.doi.org/10.7717/peerj.901>. Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals. PeerJ, 3: e901  DOI: 10.7717/peerj.901


Joseph R. Pawlik, Professor
Department of Biology and Marine Biology
UNCW Center for Marine Science
5600 Marvin K Moss Lane
Wilmington, NC  28409   USA
pawlikj at uncw.edu<mailto:pawlikj at uncw.edu>; Office:(910)962-2377; Cell:(910)232-3579
Website: http://people.uncw.edu/pawlikj/index.html<https://mail.uncw.edu/owa/UrlBlockedError.aspx>
PDFs: http://people.uncw.edu/pawlikj/pubs2.html<https://mail.uncw.edu/owa/UrlBlockedError.aspx>
Video Channel: https://www.youtube.com/user/skndiver011

From: coral-list-bounces at coral.aoml.noaa.gov<mailto:coral-list-bounces at coral.aoml.noaa.gov> <coral-list-bounces at coral.aoml.noaa.gov<mailto:coral-list-bounces at coral.aoml.noaa.gov>> on behalf of Kuffner, Ilsa <ikuffner at usgs.gov<mailto:ikuffner at usgs.gov>>
Sent: Thursday, February 16, 2017 9:18 AM
To: Risk, Michael
Cc: Eugene Shinn; coral list
Subject: Re: [Coral-List] Parrotfish loss drives reef decline

Interesting discussion, indeed. I invite those interested in this topic to
see the following review / perspectives paper:

Kuffner, I. B., and L. T. Toth (2016) A geological perspective on the
degradation and conservation of western Atlantic coral reefs. Conservation
Biology 30:706-715.

Abstract: Continuing coral-reef degradation in the western Atlantic is
resulting in loss of ecological and
geologic functions of reefs. With the goal of assisting resource managers
and stewards of reefs in setting
and measuring progress toward realistic goals for coral-reef conservation
and restoration, we examined reef
degradation in this region from a geological perspective. The importance of
ecosystem services provided by
coral reefs-as breakwaters that dissipate wave energy and protect
shorelines and as providers of habitat for
innumerable species-cannot be overstated. However, the few coral species
responsible for reef building in the
western Atlantic during the last approximately 1.5 million years are not
thriving in the 21st century. These
species are highly sensitive to abrupt temperature extremes, prone to
disease infection, and have low sexual
reproductive potential. Their vulnerability and the low functional
redundancy of branching corals have led
to the low resilience of western Atlantic reef ecosystems. The decrease in
live coral cover over the last 50 years
highlights the need for study of relict (senescent) reefs, which, from the
perspective of coastline protection
and habitat structure, may be just as important to conserve as the living
coral veneer. Research is needed to
characterize the geological processes of bioerosion, reef cementation, and
sediment transport as they relate to
modern-day changes in reef elevation. For example, although parrotfish
remove nuisancemacroalgae, possibly
promoting coral recruitment, they will not save Atlantic reefs from
geological degradation. In fact, these fish
are quickly nibbling away significant quantities of Holocene reef
framework. The question of how different
biota covering dead reefs affect framework resistance to biological and
physical erosion needs to be addressed.
Monitoring and managing reefs with respect to physical resilience, in
addition to ecological resilience, could
optimize the expenditure of resources in conserving Atlantic reefs and the
services they provide.

Best regards,

P.s. The original title for this manuscript was "Atlantic coral reefs:
Standing on the shoulders of giant wimps." Rest assured, the "wimps" in the
title was referring to the species of coral that built western Atlantic
coral reefs, not to the founding fathers of reef geology.
Ilsa B. Kuffner, Ph.D.
U.S. Geological Survey
St. Petersburg Coastal & Marine Science Center
600 4th Street South
St. Petersburg, FL 33701

Email: ikuffner at usgs.gov<mailto:ikuffner at usgs.gov>
Tel: (727) 502-8048
Fax: (727) 502-8001

On Wed, Feb 15, 2017 at 10:23 AM, Risk, Michael <riskmj at mcmaster.ca<mailto:riskmj at mcmaster.ca>> wrote:

>    Good day..
>    I  hesitate  to weigh in here, but I thought I would offer some random
>    thoughts.
>    The Kramer et al. paper is a very nice piece of work, using up-to-date
>    techniques  (some  of  which  are beyond my limited comprehension). My
>    compliments to the authors.
>    None of us should be surprised by verification of the importance of
> grazing
>    in reef systems. Personally, I think that ever since Stephenson and
> Searles,
>    Odum and Odum, Gerry Bakus and Kaneohe Bay, the vast majority of coral
> reef
>    research has simply been fine-tuning what we already know.
>    There are some aspects of the paper that are worth considering further...
>    First of all, few people in this world have looked at more well core
> than
>    have Gene, and he notes that abundance estimates from teeth must be
> taken
>    with  a grain of sand (forgive me). I note that cores were taken by "a
>    combination  of  push-coring  and vibra-coring", which produces large,
>    relatively  undisturbed  samples  but  means that you cannot core reef
>    framework. Authors are to be commended on their good dating techniques
> (age
>    reversals can be used as a proxy for storm transport, which might have
> been
>    worth noting), and one of their three sites records information of the
> time
>    scale of most interest to us: post-1900 (but there the resolution tails
> off
>    a bit).
>    This new (to me) CCM technique for teasing out causality seems to be a
>    powerful tool, but I note it works if you only consider two variables:
> as in
>    this  case.  Of  course, nutrient proxies would have been difficult to
>    obtain-but nonetheless possible.
>    Personally, I am not surprised at the lack of correlation with Diadema...
> If
>    we look closely at Gardner et al., we see that the precipitous decline
> in
>    Caribbean reefs began prior to 1960. The dieoff in populations of
> Diadema is
>    in no way reflected in that decline-the line continues its sad progress
>    without a blip.
>    My concern here is that there may be a tendency to apply these results
> to
>    rehabilitation efforts, and concentrate on bringing back the fish. It
> is my
>    impression that people with a mostly biological focus tend to believe
> that
>    reefs will recover if the grazers come back, whereas those with a more
>    varied background in chemistry and geology take a more nuanced approach.
>    As  far as I know, there is only one example from the Caribbean of the
>    response to an increase in water quality. No one should be surprised to
>    learn that the reef came back. Equally, no one should believe the reefs
> will
>    come back if only the grazers come back.
>    Mike
>    Risk, Michael
>    [1]riskmj at mcmaster.ca<mailto:riskmj at mcmaster.ca>
> References
>    1. mailto:riskmj at mcmaster.ca
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