[Coral-List] Parrotfish and coral

Douglas Fenner douglasfennertassi at gmail.com
Thu Feb 23 17:18:29 EST 2017

    Thanks!  As for African dust being the cause of the Diadema dieoff
throughout the Caribbean and Florida in 1983, there is one detail of the
dieoff that I wonder if African dust can explain.  The dieoff began in
Panama and took an entire year to move around the Caribbean.  The sequence
it moved in matches the direction of current patterns.  At individual
locations, the dieoff took only about 10 days.  How can African dust
possibly account for that pattern?  Did African dust first hit Panama, and
then move around the Caribbean following water current patterns?  Why
wasn't the dieoff synchronous across the Caribbean, and why was the dieoff
complete at one location long before it even appeared at another?  Is there
documentation of the African dust reaching the Caribbean in that pattern?
Wouldn't the dust reach the eastern islands of the Caribbean and then move
west?  Isn't that the direction that the wind usually moves?  That's how
the dust gets from Africa to the Caribbean.  How could African dust get to
Panama first before reaching the windward islands in the eastern Caribbean
many months later??
   Cheers,  Doug

On Fri, Feb 17, 2017 at 8:49 AM, Eugene Shinn <eugeneshinn at mail.usf.edu>

> Thanks to all who have weighed in and posted comments on the subject of
> parrotfish herbivory, ancient fishing, and coral growth. I learned a
> lot. The paper by Cramer, K. L., (2013) /History of human occupation and
> environmental change in western and central Caribbean Panama,/ /Bulletin
> of Marine Science /89m (4) 955-982 Is an outstanding read. The paper is
> well documented, and shows how heavily populated central America was in
> pre Columbian times before the Spanish came and obliterated more than 90
> percent of the population. And yes, they did eat fish but most of the
> damage to coral reefs then as now was mainly related to agriculture and
> runoff. To feed fish to the once large population using only fish hooks
> made from turtle shell still seems a bit of a stretch, especially
> herbivorous fish. How does one bait a hook with algae? Most likely the
> ancients used spears and nets along with fish traps. Traps are easy to
> construct from native materials and such traps are still made and used
> today in various parts of the Caribbean. Traps will certainly capture
> parrotfish while even modern metal fishhooks seldom catch these fish.
>       Other postings point out that parrotfish remove algae on dead
> coral or other surfaces thus preparing the surface for coral
> recruitment. This has long been the accepted standard explanation and
> surely applies in many areas.
>       Hanna Rempel (off line) pointed out that indeed certain parrotfish
> do bite live coral. I agree and have watched them doing so. I once spent
> a day on Looe Key reef watching parrotfish taking bites from large
> Montastraea heads. It was an especially calm day and there were small
> piles of parrotfish poop resting on the tops of several live coral
> heads. Unfortunately I was not there long enough to watch for an effect
> the defecated sand might have on the coral. Of course waves eventually
> swept the sandy material off or the coral polyps removed the sand. What
> was obvious, however, were many 3 to 5 cm dead spots supporting algae
> and/or infected with black band disease. Bite marks suggested that
> parrotfish made these areas. I had never seen parrotfish bites in
> infected with algae before. Possibly there was an overabundance of
> parrotfish because the reef is protected.
>       Now back to my earlier comments concerning Carysfort reef in the
> Florida Keys. I have been taking serial photos there for the past 56
> years. Three summers ago I spent a day there with Phil Dustan who had
> done the most significant monitoring work there in the 1970s when it was
> a beautiful live /Acropora/ reef. At Carysfort all the /A. palmata/ and
> virtually all the backreef /A. cervicornis/ was dead and had been
> converted to rubble. Parrotfish were have a field day. They were biting
> coral that had died back in the mid 1980s. There had been virtually no
> recruitment there in the 30 or more years since. At the rapid rate the
> parrotfish and roving bands of blue tangs are munching the dead coral an
> abundance of reef sand has been created. That reef sand no doubt
> contains fish teeth. Now spring ahead a hundred years and assume the
> coral are flourishing and take some cores of the reef. Where would the
> parrotfish teeth be? Would they not be in the sediment associated with
> the period of time when the reef was dead and plenty of algae to eat? If
> you counted the abundance of the teeth in the sandy part of the cores
> would you conclude the parrotfish had killed the reef? Or would you
> assume the fish died thus causing the corals to die? Or was it
> pollution/disease/or climate change or something else, possibly African
> dust that killed the reef?
>       That parrotfish herbivory is not needed to stimulate coral reef
> growth has been shown by others, Auchley A. McField MD. Alverez-Filip L.
> (2016) /Rapidly increasing macroalgal cover not related to herbivorous
> fishes on Mesoamerican reefs/. PeerJ 4:e2084
> <https://doi.org/10.7717/peerj.2084>their observations on the Belize
> reef tract are well documented.
>       Kauffman has suggested hurricanes might kill and cause rubble to
> become algal infested. That could also lead to parrotfish increases.
> That event was well documented in Jamaica.
>        When hurricane Donna decimated Grecian Rocks reef in 1960 the
> reef did not become algal infested. In fact most broken fragments of
> branching corals began growing and the reef area expanded. We documented
> the storms effect. (Ball, et al 1967), and the recovery (Shinn 1976).
> The same happened in 1965 when Betsy decimated the same reef. Again the
> reef recovered. However, the reef did not recover after 1990 when
> hurricane Andrew swept though the upper keys. Something had changed and
> algal infestation became rampant. There were no longer /Diadema/ to
> remove the algae (they had died in 1983) but there were sill abundant
> parrotfish. Some time ago I proposed that the 1983 increase in algal
> turf was related to the Caribbean-side demise of /Diadema/ and the
> effects of African dust. (Lessios, et al 1984) had shown that /Diadema/
> demise was Caribbean-wide. Monitoring of African dust by Joe Prospero
> showed the dust had blanketed the Caribbean in 1983; He had been
> monitoring dust in the eastern Caribbean since 1965 and showed 1983 to
> be the peak year of dust flux to the Caribbean. (Shinn, E. A. Smith, G.
> W., Prospero, J. M, Betzer, P., Hayes, M I, Garrison, V. Barber. R T.,
> 2000, /African dust and the demise of Caribbean coral reefs/: Geological
> Research Letters, v. 27, P. 3129-3132). Many will say it was sewage and
> increasing population in the Keys that cause demise. However that does
> not explain why the same events were happening simultaneously to reefs
> around small islands throughout the Caribbean. Dust flux remains high
> and a recent unfunded and unpublished preliminary testing of African
> dust collected from the air showed it to be lethal to A/. cervicornis/.
> Why it is toxic is not known but our earlier work at USGS showed that in
> addition to the nutrients iron, and phosphate, the dust coincidentally
> contains (copper, mercury, arsenic, radiogenic beryllium 7, lead 210,
> various pesticides, and approximately 200 viable species of bacteria and
> fungi) Possibly some of these ingredients can affect coral growth. But
> that's another story. Hopefully some day someone will do the work needed
> to determine exactly what is in the dust that affects coral and people)
> but do not expect any government agency to fund the research. Everyone
> who has written a proposal to do so has been turned down. Is more study
> needed? You bet! Gene
> No Rocks, No Water, No Ecosystem (EAS)
> ------------------------------------ -----------------------------------
> E. A. Shinn, Courtesy Professor University of South Florida College of
> Marine Science Room 221A 140 Seventh Avenue South St. Petersburg, FL
> 33701 <eugeneshinn at mail.usf.edu> Tel 727 553-1158
> ---------------------------------- -----------------------------------
> --
> No Rocks, No Water, No Ecosystem (EAS)
> ------------------------------------ -----------------------------------
> E. A. Shinn, Courtesy Professor
> University of South Florida
> College of Marine Science Room 221A
> 140 Seventh Avenue South
> St. Petersburg, FL 33701
> <eugeneshinn at mail.usf.edu>
> Tel 727 553-1158
> ---------------------------------- -----------------------------------
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Douglas Fenner
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