[Coral-List] parrotfishes and coral reef health

[Noah van Hartesveldt]

Hi Les,

This is an interesting idea that I have been looking at in the Grape Tree Bay reef off of Little Cayman Island. We looked at the presence of grazers, macroalgae and resheeting(new tissue growth over long dead skeletons) while evaluating the current state of A. palmata in GTB. We had previously noted a significant number of these long dead a. palmata skeletons(LDAPS) in GTB - some covered with MA and others with new colonies growing over them.

To determine if the macroalgae might be impeding new recruitment or further resheeting on long dead skeletons, we have GPS located and catalogued all LDAPS. We have devised a method of physically scrubbing the LDAPS to remove MA - to determine if the MA is impeding coral growth. We also have physically tagged random LDAPS that were either subjected to scrubbing or left as controls. We will be revisiting these this summer. 

After the WBD epizootic in the 80s and subsequent, frequent bleaching events, I wonder as well if hurricanes could have been the capstone to a series of factors contributing to A palmata's failed recovery. It will be interesting to see what, if any, role macroalgae cover has in coral recruitment. 

Thank you,

Noah van Hartesveldt


> On Feb 15, 2017, at 10:07, Kaufman, Leslie S <lesk at bu.edu> wrote:
> 
> Hi Charles.  My suspicion is that hurricanes can tip coral to macro algae permanently, especially if things are already headed that way.  If they already are that way, then areas denuded by such a storm would be likely be quickly recolonized (or covered through regrowth) by the macrophytes, rather than switching over to coral dominance.
> 
> It’s an interesting idea, though- I mean that hurricanes could contribute to a shift from macrophyte dominance to coral.  I guess you’d have to imagine a scenario in which a macrophyte-dominated reef had very high Diadema or scarine densities, sufficient to throw storm-bared patches to CCA (crustose coralline algae) very quickly.  I spent several months going around fleshy algal reefs with Walter Adey in 1975, but never saw the appropriate maidens-in-waiting for such a thing to occur.  Diadema densities were generally low except in a few small, concentrated patches where surface rugosity was very high, and the herbivore community was striking deficient in hard grazers.  My thought back then was that these Diadema patches were the nucleating points for the reverse phase shift transition (shift to coral dominance, for those who don’t get off on phase shit talk).
> 
> Another place that might offer some insight is the Abrolhos Bank in Brazil..  Here we have discovered vast reaches of fleshy algal pavement ranging from very shallow (a couple of meters) around the Abrolhos Archipelago, to between 30 and 40 meters across the whole middle and outer reaches of the Bank (we is a team I’ve been part of led by Rodrigo Moura, Ronaldo Francine-Filho, Guilherme Dutra and others).  This has to be the very strangest place I have ever been under water.  Mostly on the inshore side of the Bank are coral reefs dominated by the endemic genus Mussismilia, plus Siderastrea, Millipore, Montastrea cavernosa, and big cheilostome bryozoans.  Around the archipelago you can find alternating patches of coral community and fleshy algal pavement.  Benthic patch dynamics appear to be driven in part by the endemic budiao azul parrotfish, Scarus trispinosus, a hard grazer similar in appearance to the midnight parrot but possibly more closely related to the rainbow.  When storms hit the archipelago, I suppose it really might be possible that macrophyte peeled from volcanic rock could give way to the birth of a patch of coral community.  We know that storms can dramatically impact the macrophyte community, rather like seasonality in California kelp forests along the mid-coast.  Up and down the outer Abrolhos Bank are vertical depressions to shafts that resemble sinkholes superficially, but aren’t.  These are called buracas (holes), and are described here: http://www.sciencedirect.com/science/article/pii/S0031018216304618.  If you run a search on “Abrolhos”, “buraca” or “rhodolith” and “Brazil” the whole lot of papers on benthos, fishes, and geology should pop up.  Winter storms rip up large quantities of macrophyte material, which settles into the buracas, rots, and further erodes the carbonate.  The insides of these things somewhat resembles a Vinogradsky column when they are full of algal debris. Are there places that can be shifted to coral community dominance by winter storms?  Well, there are scattered emergent old reef structures inhabited by CCA, sponges, and a few corals- so maybe those.  We are talking pretty deep here.  Otherwise, however, areas where the macrophytes have been ripped away mostly seem too be rhodolith fields.  So on the east and northeast side of the Abrolhos Bank, the dominant hard bottom habitat types are reef-like rhodolith beds, and rhodolith beds covered by fleshy algae, making them fleshy algal pavements.  I would not be at all surprised if patch dynamics out there are largely storm-mediated.  I suspect that isn’t what you were thinking about, though.
> 
> Les
> 
> 
> Les Kaufman
> Professor of Biology
> Boston University Marine Program
> Faculty Fellow, Pardee Center for the Study of the Longer-Range Future
> and
> Conservation Fellow
> Betty and Gordon Moore Center for Science
> Conservation International
> lesk at bu.edu<mailto:lesk at bu.edu>
> 
> 
> 
> On Feb 15, 2017, at 10:25 AM, Charles Delbeek <cdelbeek at calacademy.org<mailto:cdelbeek at calacademy.org>> wrote:
> 
> Les could you comment on the role that hurricanes and severe storms play in this scenario? I would think that such events would scour reef surfaces as well as any herbivore but the lack of grazers may not prevent their rapid recolonization?
> 
> 
> J. Charles Delbeek, M.Sc.
> Assistant Curator, Steinhart Aquarium
> California Academy of Sciences
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> On Tue, Feb 14, 2017 at 10:25 AM, Kaufman, Leslie S <lesk at bu.edu<mailto:lesk at bu.edu>> wrote:
> Hi everybody.
> 
> So I’ve been following this herbivore engagement, and I am puzzled about one thing.  As experienced coral reef scientists, why are we insisting on taking such an over simplistic view of things?  I think Gene was on the right track here.  Or maybe he just wasn’t on any track, and this was healthy.
> 
> Where the field is at, is that we’ve acknowledged that the relationship between herbivory and reef benthic communities is not best approximated by linear (as in straight line) models, and may not even be best fitted to curvilinear relationships (as in still assuming global consistency, or a single equation for the entire graph volume).  Like everything else on a coral reef (or in your mouth) herbivore-benthic dynamics on oral reefs are complex.  Within certain limited domains in space and time, a simple, straightforward model is fine.  Speaking broadly, circumstances vary, a lot, and so do the rules of community organization.
> 
> What we’ve been trying to figure out is how the rules work in any particular segment of the parameter space within which coral reefs can exist, and where you fall out of that space (or off of the manifold encompassing the range of possible conditions in which coral reefs of some sort can exist)..
> 
> So, for example, take Diadema antillarum.  Several decades ago, when seemingly healthy coral reefs were still a thing in the Caribbean, Diadema played a critical role in maintaining hard coral dominance, as a grazer, most particularly on the reef crest and shallow fore and back reefs, to a depth of about 8 meters, and then rapidly falling off in abundance and influence as you headed out into deeper water.
> 
> What many had not noticed is that the herbivorous fish communities over much of the tropical west Atlantic were already severely overfished.  Well, in Jamaica it was hard not to notice this because the low fish biomass was so extremely low, but elsewhere I suppose it could slip by.  Grazing fishes also peaked in biomass in shallow water, where the reef crest was attended by Sparisoma rubripinne, S. viride, and Scarus vetula particularly, plus in some places sizable schools of Scarus coelestinus and to a lesser extent S. guacamaia.  The parrotfishes were coeval with large schools of Acanthurus coeruleus with varying amounts of the other two acanthurids mixed in.  Except in places where they’d been fished out.
> 
> The urchins must have been extremely important because when they croaked in the early 1980’s epizootic, there were big blooms of macro algae followed in many places by the establishment of a blanket of recalcitrant, long-lived macrophytes, usually including Dictyota spp. and Lobophora variegate.  Poorly grazed shallows became infested in many places with Sargassum and Turbinaria.  In Florida, where the taking of herbivores was banned as early as 1980, grazing pressure was (and now is) fairly high in many places.  This has not guaranteed a return to coral dominance, though.  Sometimes, for some reason, corallines fail to resurge.  Sometimes there are corallines but still very little settlement of framework-significant corals- possible recruitment limitation now that coral reef condition is so diminished as to compromise both self-recruitment locally, and rescue through larval connectivity.  We are living in the Age of Lags.  Under such circumstances, it is dangerous to jump to conclusions about how things are working…how they are working may be working very slowly.
> 
> Within this broad setting there are an amazing number of bizarre possibilities.  For example, even decades ago, the eastern Antilles were dominated by fleshy algal pavements (and still are).  Herbivore biomass there varied, but was mostly concentrated in browsers (both urchins and fishes), not grazers, which may have operated so as to perpetuate the reign of the macrophytes.  At least we suggested as much back in 1977.  This is still the basic nature of fish and urchin assemblages associated with fleshy algal pavement.  They are similar to seagrass communities in this regard.
> 
> In other places the densities of Diadema were so incredibly high (and they were BIG) that what you’d see is a carbonate moonscape with big gouges taken out of the coral rock, which itself was shot through with clionid sponges and other bioeroders.  One place this was very obvious was in Guadaloupe, but recently I saw something of this sort right outside Half-moon Bay on the west end of Jamaica.  It can still happen, even now.
> 
> I think before we make broad generalizations about herbivores and coral reefs, we need to define the state space and clearly indicate where in it we are talking about.
> Much more interesting than assuming the whole world works exactly the same way, and ultimately, a much more powerful perspective as well if you want to make predictions.
> 
> Les
> 
> Les Kaufman
> Professor of Biology
> Boston University Marine Program
> Faculty Fellow, Pardee Center for the Study of the Longer-Range Future
> and
> Conservation Fellow
> Betty and Gordon Moore Center for Science
> Conservation International
> lesk at bu.edu<mailto:lesk at bu.edu><mailto:lesk at bu.edu<mailto:lesk at bu.edu>>
> 
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