Coral mortality II
Hector Reyes Bonilla
hreyes at calafia.uabcs.mx
Thu Jan 15 13:21:43 EST 1998
Dear coraleros:
Thank you very much for the numerous responses, to my address and
to the coral list; I hope that this mess would be useful for someone
else.
As I noticed that the interest is wide (I never suspected), I
would like to detail a little bit our observations in Mexico. In June we
find the first bleached corals. Their number increased a lot in the
following two months, but it was in August and September when we look at
the first dead colonies. Since June, we marked about 50 bleached colonies in
several localities, to see what happende to them. The mortality was
strongly size- dependent: small corals (about 15 x 15 cm) died in less
than a month, and larger ones survived even to this day (yesterday we
went to look at them). The original question as if corals died by
themselves or were killed. Well, in a number of cases they were actually
killed. We saw colonies covered, for example, by Caulerpa, which had
living polyps still. Few days later, the coral was dead and the algae was
entangled around. Polyps most surely died by lack of food (no light
needed) or chemical poisoning (or something like that). The same occurred
when sponges covered them, and if filamentous algae attack them. It is
interesting that, as Dr. Szamant mentioned, the center of the colony was
more affected in this case, but when Caulerpa or sponges attacked, they
started in the edges of the coral. I hope that this info would be useful.
Thanks for your interest. Ah! By the way, I only heard of one reference
about algae killing corals (although not related to ENSO; thanks Jan
Korrubel). Saludos!
Hector Reyes
Depto. Biologia Marina. UABCS
La Paz, MEXICO.
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