[Coral-List] Parrotfish and coral

[Eugene Shinn]

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 
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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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