More Coral Bleaching in Hawaii
Steve Coles
slcoles at bishop.bishop.hawaii.org
Fri Sep 20 15:44:46 EDT 1996
Yesterday (19Sep96) I observed moderate coral bleaching on the reefs of
leewad Oahu, Hawaii from Nanakuli to Kahe Point and to depths of 8 m. From
these observations, it can be assumed that this condition extends to the
entire western side of Oahu, the first time that it has been reported from
this area. In contrast to the total zooxanthellar pigment loss reported
last week for corals in two areas in embayments on windward Oahu, the
present bleaching is partial and limited to three species. Pocillopora
meandrina is most affected, with about 5% of the colonies observed having
lost pigmant on their branches but retaining some zooxanthellar pigment in
their branch bases, resulting in a pale coral with the pink to rose coral
characteristic of coral tissue pigments. Encrusting Montipora capitata
(=verrucosa), present in low abundandance, is totally bleached, while
encrusting Montipora patula ranges bleached to normal. The dominant coral
in the area, Porites lobata, with a few exceptions, is generally unchanged.
This is the first time this phenomenon has been observed in this area in 25
years of monitoring. This is a completely open coastline with no
opportunity for restriction of circulation that would promote localized
heating of ambient water. Temperature measured at the time was 27.0-27.2
deg. C. Intake temperatures continuously monitored by the nearby Kahe Power
Station will provide a record for the last month which can be correlated
with this event.
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