Coral mortality II

Hector Reyes Bonilla hreyes at
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 
	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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