[Coral-List] Palythoa interactions, bleaching

[William Allison]

At permanent sites in a variety of contexts observed for 17 years in
the Maldives, several species of Palythoa have occasionally been seen
in contact with corals. On average the outcome is a draw.  Under
unusual circumstances, such as temperature/light-induced bleaching
events, of which there have been several, Palythoa bleached at about
the same time as more sensitive corals, recovered at much the same
rate, but had lower mortality rates. During the 1998 bleaching event
Palythoa suffered mortality but less than did corals. Since then both
permanent sites and random surveys have shown little growth and no
gains with respect to corals on average. Some Palythoa have bite marks
but I have not observed the predator.

In addition to previously posted references pertaining to
Palythoa-coral interactions:

Mueller, E. M. (1992). "Palythoa caribaeorum: an indicator of coral
reef perturbation." Proc. 7th ICRS 1: 72.

Thomassin, B., 2000, Coral List. Summary note - anecdotal account - go
to the archives for his exact words: competition between Palythoa and
corals was very common on reef flats with enhanced nutrient inputs and
current action. Additional factors were suggested in examples from
three different locations (large anthropogenic impact, nearby nickel
factory and heated water, sewage discharge and wave action).
Thomassin cites:
Herbert, C. (1972). "Contribution a l'etude ecologique de quelques
zoanthaires temperes et tropicaux (Contributlon to the ecological
study of some temperate and tropical zoanthids)." Marine Biology
13(2): 127-136.