Coral mortality

Anne Cohen acohen at
Wed Jan 14 18:12:31 EST 1998

Hector Reyes Bonilla wrote:
>         Dear coraleros:
>         I have been looking for data on why corals die after they were
> bleached. In the beginning, I thought that it was a physiological problem
> or so, but after following bleached corals in the Gulf of California for
> several months, I observed that most of them die because of overgrowing
> of other species (mostly algae), and not by "natural causes". Do you know
> of any paper doing explicit reference of this? Thanks.
>         Hector Reyes
>         UABCS, Depto. Biologia Marina
>         La Paz, BCS, MEXICO

Dear Hector,
Your deduction is an interesting one. During your observations, were you
able to tell whether the colonies had been killed by bleaching and were
subsequently overgrown by algae, or whether they had bleached, weakened
and then been killed by algal overgrowth ?  In my experience, many
bleached colonies maintain live polyps throughout the bleaching event.
These colonies generally recover, probably because they are able to
prevent algae from colonising/settling on the surface of the coral.
Bleached colonies which lose their polyps as a consequence of bleaching
are overgrown by algae in a matter of days or weeks.
I posted this reply list-wide because I would be interested to hear
others' comments on this subject

Anne Cohen.

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