[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
President
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org
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