[Coral-List] coral bleaching in American Samoa

[Doug Fenner]

   A mild coral bleaching event is currently underway in American Samoa.  About 1/4 to 3/4 of living staghorns are at least partially bleached in 3 lagoons on Tutuila.  Only upper surfaces of horizontal branches have any bleaching (usually it is only partial even on upper surfaces); undersides always retain some color.  No colonies are totally bleached, none recently dead.  A few A. palifera and A. cf. listeri are bleached, but there are very few colonies of these species in the lagoons.  Other species are not bleached.  Bleaching was first seen on March 20.  The last previous check of these corals was on Feb 28.
     Temperature loggers in one lagoon show temperatures rising to a peak averaging a little over 30C in mid-February, and remaining fairly steady since then.  Peak temperatures reach 32C for a few hours on some days.  These 3 lagoons have little water circulating into them at low tide.  Similar areas with the same staghorns that have open circulation with the ocean have very little bleaching (about 1-5%).  Reef fronts that have been looked at also have no bleaching, but do not have these staghorns.
    I am told that last year there was strong bleaching of the staghorns, and there was bleaching in the previous summer as well.  About half of the lagoon staghorn beds are dead and covered with algae, appearing to be dead at least a year.  This is true of the places with open circulation as well as the closed circulation areas.
    -Doug Fenner
Chief Biologist
Dept. Marine & Wildlife Resources
American Samoa