[Coral-List] Coral diseases and algae

[Thomas Goreau]

>
Dear Gene,

When I first began photographing YBD in Jamaica in 1987 we thought it  
was delayed recovery from bleaching, and it took Craig Quirolo five  
years to convince me it was a disease. Discovery Bay nutrients reached  
eutrophic levels in the early 1980s, long after overfishing had taken  
its toll, and the corals were being overgrown with algae.  On those  
corals that were part of my long term coral growth monitoring study, I  
would systematically weed back any algae that could overgrow the  
corals, and it made no difference to the corals with YBD, just as the  
new paper suggests.

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........

For the detailed non-parametric statistical correlations based on  
extensive ecological assessment of 26 ecological and environmental  
parameters at 47 sites, including those between algae and coral  
diseases, see the first paper and appendices at:
http://globalcoral.org/Turks and Caicos Islands Coral Reef Health  
Assessment.htm

Best wishes,
Tom

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
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org

> Date: Fri, 20 Feb 2009 09:53:51 -0500
> From: Eugene Shinn <eshinn at marine.usf.edu>
> Subject: [Coral-List] Do corals need fish to remain healthy?
> To: coral-list at coral.aoml.noaa.gov
> Message-ID: <a0623090bc5c34a2c6813@[131.247.137.127]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
>
> The Program Manager at the Florida Keys National Marine
> Sanctuary  recently made me aware of a new paper titled, "Macroalgae
> Has No Effect on the Severity and Dynamics of Caribbean Yellow Band
> Disease." Ivana Vu et. al, 2009, published in PloS Feb 09 Vol 4 Issue
> 2. The paper is the result of an ingenious  manipulative field study
> in Puerto Rico. As the title implies it shows, that various
> Macroalgae have no effect on CYBD in Montastraea faveolata . This
> conclusion contradicts the widely repeated mantra that these algae
> stimulate coral disease by serving as a reservoirs of pathogens  and
> that their proliferation on reefs is due to removal of herbivorous
> fishes. In other words, remove fish (overfishing) that eat algae and
> the algae will grow and cause decline of coral.
> When I read the paper I was reminded of a recent conversation with
> Harold Hudson of Reef Tech  who described to me what he recently saw
> in Roatan. "It was the biggest healthiest staghorn coral forest I
> have seen in many years", he said.  What caught his eye also was that
> there were essentially no fish! Not even the ubiquitous Damsel fish
> that normally thrive among staghorn branches. It was wonderful to
> hear that such healthy staghorn fields still exist but isn't it odd
> that it is thriving  without the usual tropicals, surgeon, and parrot
> fish? Similar observations have been recorded by J. Keck et al.,
> "Unexpectedly high cover of Acropora cervicornis on offshore reefs in
> Rotan (Honduras)" published in Coral Reefs, DOI
> 10.1007/s00338-005-0502-6  and also confirmed in a paper by B. Riegl
> et al, Offshore refuge and metapopulation resilience explains high
> local densisty of an endangered coral (Acropora cervicornis). In
> Marine Pollution Bulletin.  Many of us can remember the luxurious
> corals on the North coast of Jamaica before the early 1980s at a time
> when the area had already been fished out. Apparently what ever
> started the general Caribbean decline in the late 1970s and early
> 1980s remains  somewhat elusive but widespread.  I suggest we need
> more straight-forward in-the-field experiments such as the Puerto
> Rico study cited at the beginning.  May be we should  rethink the
> commonly cited association between fishing and coral health??  Gene
> -- 
>
>
> No Rocks, No Water, No Ecosystem (EAS)
> ------------------------------------  
> -----------------------------------
> E. A. Shinn, Courtesy Professor
> University of South Florida
> Marine Science Center (room 204)
> 140 Seventh Avenue South
> St. Petersburg, FL 33701
> <eshinn at marine.usf.edu>
> Tel 727 553-1158----------------------------------
> -----------------------------------