[Coral-List] Marine Protected Areas, fish, corals, algae, and diseases

Thomas Goreau goreau at bestweb.net
Tue Feb 24 14:07:30 EST 2009

John makes a very important point about the failure of marine  
protected areas to protect corals, and indeed every marine protected  
area I go to is full of dead or dying corals, being killed by factors  
they cannot control.

But the argument may also apply to fish according to a very  
interesting paper:
Jones, McCormick, Srinivasan, and Eagle, 2004, Coral declines  
threatens fish biodiversity in marine reserves, PNAS 101:8251-8253
They showed that "protected" areas and open entry fishing areas had  
equal declines in coral cover and in fish diversity.

This study was done in Papua New Guinea, and coincidentally James  
Cervino and I had shortly before done a study of coral and sponge  
diseases in the same area. What we found was that the "protected" and  
"fished" reefs studied by Jones et al. were both fringing reefs along  
the coast, and they were very severely impacted by fresh water, mud,  
sewage, fertilizers, and agricultural chemicals brought in by the  
rivers, that they had very high levels of coral disease, and very high  
levels of weedy algae overgrowth on corals. Yet in contrast the reef  
corals and fish were much better, and the algae far less, on the  
inshore slope of an offshore bank reef only a hundred meters or so  
offshore, far better still on the open side of that bank, and still  
finer on the open ocean pinnacle reefs. Because the local fishermen  
cannot afford boats, they only harvest the fringing reefs and cannot  
get to reefs only a hundred meters offshore. But the impression given  
by the algae abundance and coral health was that when corals declined  
due to eutrophication, the fish vanished with them, whether protected  
or not.

So to turn John's circular reasoning a step further, if we want to  
protect fish, the first thing to protect is the corals!

Thomas J. Goreau, PhD
President, Global Coral Reef Alliance
Coordinator, United Nations Commission on Sustainable Development  
Partnership in New Technologies for Small Island Developing States
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

> Date: Tue, 24 Feb 2009 10:55:44 -0500
> From: John Bruno <jbruno at unc.edu>
> Subject: [Coral-List] Coral diseases and algae
> To: coral-list at coral.aoml.noaa.gov
> Cc: Bill Precht <bill.precht at noaa.gov>,	"Richard B. Aronson"
> 	<raronson at disl.org>
> Message-ID: <D32288DF-7820-4877-893F-C991F8344EFC at unc.edu>
> Content-Type: text/plain;	charset=UTF-8;	format=flowed;	delsp=yes
>> By the way the effect of overfishing in Jamaica was not to eliminate
>> herbivorous fish, as top-down dogmatists would have us believe, but
>> precisely the opposite. In the early 1950s the reef was dominated by
>> predatory and invertebrate eating fish, and there were very few
>> herbivorous fish. After overfishing and coastal eutrophication the
>> fish population switched to overwhelmingly herbivorous species,
>> because that is all the food there is now. So the problem is not lack
>> of grazers at all, but that the over-fertilized algae grows so fast
>> that no grazers can control them.
>> However I am not sure this lack of obvious algae interaction applies
>> to other coral diseases than YBD. Jennifer Smith and colleagues, and
>> Maggie Nugues and colleagues, have made convincing cases for possible
>> interactions of coral disease pathogens and algae based on lab
>> experiments and small scale field associations. We found very strong
>> associations between many diseases and certain algae quite
>> unexpectedly from data analysis of large scale studies of coral reef
>> health in the Turks and Caicos Islands. All the coral diseases that
>> were abundant enough to be tabulated at all sites (White Plague,  
>> Black
>> Band Disease, Gorgonian Disease) were significantly associated with  
>> at
>> least one algae genus. However YBD was too rare there to
>> tabulate........
> One could take Tom's arguments above a step further (perhaps into the
> realm of absurdity) by pointing out that were there indeed conclusive
> evidence that too much macroalgae and a lack of herbivorous fish was
> the proximate cause of coral diseases (including bleaching as the
> proponents of this idea argue) then the logical management action
> would be to cull carnivores to protect herbivores.  Knowing that
> predators in part control prey populations, it must be a confusing
> message for managers to simultaneously hear that they have to maximize
> predator biomass and diversity AND that of herbivorous fishes,
> including not just their densities but also their function, i.e.,
> grazing which is probably strongly controlled by predator presence via
> a Non-Consumptive Effect or TMI.
> And to take this whole argument full circle, I'd like to point out the
> very nice paper by Coelho and Manfrino (2007) that compared coral
> loss, disease and bleaching inside and out of MPAs on Little Cayman
> Island in the Caribbean.  They found fish had no measurable effects:
> "Mean live coral cover decline was similar inside (from 29% to 19%)
> and outside (from 24% to  14%) marine no-take reserves. No signi?cant
> di?erence in disease prevalence or clear pattern in  bleaching
> frequency was observed between protected and non-protected areas. It
> is concluded that  more comprehensive management strategies are needed
> in order to e?ectively protect coral  communities from degradation."
> Coelho, V.R. and C. Manfrino (2007) Coral community decline at a
> remote Caribbean island:  Marine no-take reserves are not enough
> Aquatic Conserv: Mar. Freshw. Ecosyst. 17:666-685 DOI: 10.1002/aqc.822
> John Bruno
> Associate Professor
> UNC Chapel Hill
> www.brunolab.net
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