[Coral-List] Parrotfish loss drives reef decline
riskmj at mcmaster.ca
Fri Feb 17 09:40:48 EST 2017
Good day, all.
Partly a response to the posts by Ilsa and Joe, and partly housekeeping…
In an earlier post, I referred to what I think is the only Caribbean example
of what happens when the water is cleaned up. This occurred at Worthing,
Barbados. There was a semi-enclosed lagoon tucked in behind a huge offshore
bar. That lagoon was stagnant, heated up…WQ was crap, one could find
recently-dead Diadema and corals.
Beginning in the early 2000’s, the beach eroded-this was accelerated by the
passing of Hurricane Lili on 2002. Blew the back end off the lagoon,
suddenly filling it with (relatively) clean water passing east-to-west.
Over the next year, corals (typical Caribbean sediment-resistant species)
recruited to the area; numbers of fish increased, as well as numbers of
reef-associated molluscs. The only surprising element here would seem to be:
this is the only Caribbean example we have of the influence of cleaner
There is an abstract describing this (Risk et al.), in the 2008 ASLO Summer
Meeting in St John’s NL. Writing up the full paper was on my bucket list-but
the project was done with Baird and Associates, and I will no longer work
with them. What you see in the Abstract is all you are likely to get. The
experiment has ended now, with regrowth of the blocking bar. The ambient WQ
on Barbados is probably not good enough, anywhere on the island, to support
healthy reef growth.
Ilsa’s efforts quantifying the bones of dead reefs are to be commended-but
as she points out, grazing is now destroying habitat. What is more,
bioerosion increases in lockstep with nutrients-so those bones are being
gnawed on from the outside and destroyed from the inside. So Joe’s
observation is correct: sponges now rule.
The boring sponge fauna seems to be circum-global, probably because they
pre-date the critters in which they bore. The only major species seemingly
restricted to the Caribbean is the faecal bioindicator Cliona delitrix- I
have been told that huge red colonies of the sponge, many square metres in
area, can now be seen from a light plane in the passes in Florida.
In a series of older papers, Kobluk, James and Pemberton document what
happened: borers are ancient. The “modern” fauna is virtually complete by
the Devonian. When a mass extinction comes along and wipes out their hosts,
the borers hide in hardgrounds, waiting for the rise of the next skeletal
group. They are down there now, waiting.
Re Parrotfish: it is likely that Diadema was always the dominant grazer in
the Caribbean. In a series of elegant older papers, my old mate Sammarco has
compared biological processes between the Caribbean and the Indo-Pacific.
Coral larvae in the Caribbean settle on the tops of the substrate where they
would be easy prey for visually-cued fish, whereas Indo-Pacific coral larvae
are cryptic-even when grazing pressure is removed. Basin-wide changes in the
behaviour of coral larvae are unlikely to have risen spontaneously in the
On Feb 17, 2017, at 7:15 AM, Pawlik, Joseph <pawlikj at uncw.edu> wrote:
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. 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. 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. 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. 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; Office:(910)962-2377; Cell:(910)232-3579
Video Channel: https://www.youtube.com/user/skndiver011
From: coral-list-bounces at coral.aoml.noaa.gov <coral-list-bounces at cor
al.aoml.noaa.gov> on behalf of Kuffner, Ilsa <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
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.
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
Tel: (727) 502-8048
Fax: (727) 502-8001
On Wed, Feb 15, 2017 at 10:23 AM, Risk, Michael <riskmj at mcmaster.ca>
> Good day..
> I hesitate to weigh in here, but I thought I would offer some random
> 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
> in reef systems. Personally, I think that ever since Stephenson and
> Odum and Odum, Gerry Bakus and Kaneohe Bay, the vast majority of coral
> research has simply been fine-tuning what we already know.
> There are some aspects of the paper that are worth considering
> First of all, few people in this world have looked at more well core
> have Gene, and he notes that abundance estimates from teeth must be
> 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
> reversals can be used as a proxy for storm transport, which might have
> worth noting), and one of their three sites records information of the
> scale of most interest to us: post-1900 (but there the resolution tails
> 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
> we look closely at Gardner et al., we see that the precipitous decline
> 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
> rehabilitation efforts, and concentrate on bringing back the fish. It
> is my
> impression that people with a mostly biological focus tend to believe
> reefs will recover if the grazers come back, whereas those with a more
> varied background in chemistry and geology take a more nuanced
> 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
> come back if only the grazers come back.
> Risk, Michael
> riskmj at mcmaster.ca
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