[Coral-List] Porites Line Disease

Thomas Goreau goreau at bestweb.net
Thu Nov 22 22:54:42 EST 2007

Far and away the most common disease syndrome in the Indo-Pacific is  
what I call Porites Line Disease, which has many forms and is very  
widespread and abundant, affecting primarily massive Porites, but  
also branching species. The white or grey lines are by far the most  
common, followed by brown, pink, and blue. I first noticed this  
disease in the Marshall Islands in 1997, and since then have noticed  
it on every single dive in the Pacific and Indian Oceans. I have  
pointed it out to local researchers almost everywhere, only a few of  
whom had noticed it. I have not had the time, money, hardware, or  
software to grab or tabulate the thousands of video images I have  
taken of it all across the Indo-Pacific, or formally described it in  
a paper. Although I am not aware of any publications on this  
syndrome, I know that several researchers have followed its progress  
at specific sites, and may have published descriptions, but I am not  
sure what they have called it.
PLD is distinguished by a narrow line of necrotic tissue, usually  
around a millimeter wide, which separates live from dead tissue. The  
color of the line can vary between white, grey, brown, pink, blue, or  
purple. The disease advances on the order of centimeters per month or  
more, as can be seen in the fact that in many cases, the height of  
the living tissue (which grows upward at around one centimeter per  
year is not much higher than the dead surface). The pink line variant  
was independently discovered and has been described in published  
papers in India as Pink Line Disease by Ravindran and the Raghukumars  
who isolated a fungus from samples in Lakshadweep (where it was the  
most common variant, and where I looked at with Ravindran in 1998),  
but they did not look at other color variants, and it is not clear if  
the fungi is a primary pathogen or a secondary opportunist. Because I  
work with no funding I have never been able to take microbiological  
samples for genetic sequence analysis, so I do not know if each of  
these many different color lines are different manifestations of the  
same basic disease, or if each is associated with different  
pathogens. Much microbiological work is clearly needed.

What is especially alarming about this disease is that although it is  
much slower and affects many less species than White Plague (or what  
some call White Syndrome when they can't find Aurantimonas  
coralicida), it is progressively killing the species that are the  
major survivors of all habitats that have been severely stressed,  
whether by bleaching or sedimentation. People should be aware of this  
and look out for it.

Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

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