Bleaching, Phoenix Islands, Kiribati

[David Obura]

Dear Al,

We were in the Phoenix Islands, Kiribati, at about 4 S and 173 W, part
of the same island group as Baker and Howland.  At the time of our
surveys, June 10 to July 5, there was minor bleaching, or rather paling,
of some corals in the lagoons of the two largest islands, Kanton and
Orona.  Both islands were surveyed towards the end of the period.  Once
back in the 'real world', I saw that this corresponded with 2-3 weeks of
DHWs on the NOAA maps, hence too early to make any conclusion on the
role of temperature.  Corals affected were principally Acropora spp. and
Echinopora,with less than 5-10% of colonies affected in some patches. At
the time I thought it looked more like 'normal' paling of lagoon corals
due to turbidity or lack of circulation.

Putting together Samasoni Sauni's report of bleaching in Tuvalu at the
same time as these observations, and Al's hotspot warnings further north
now (6 weeks later), it looks like a warm water pool may have moved
north.

Water temperatures were measured at just under 30C the entire trip,
using a temperature logger carried by a diver (the detailed data is
still being analyzed), and we placed 7 loggers at various depths and
reef zones (5/15/35m, leeward/windward/lagoon) for collection in the
future.

On an expedition in 2000 in the same months we did not notice any
obvious signal of coral bleaching or mortality.  We don't know if
temperatures measured were higher in 2002 than usual, though it was our
impression that the water was warmer than in 2000.

We will try and obtain reports of any current bleaching from the islands
from the i-Kiribati residents, and report those ASAP.

regards,

David Obura

Some info on the expedition can be found at http://www.neaq.org/phoenix

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David Obura
CORDIO-East Africa
P.O.BOX 10135, Mombasa, Kenya
Tel/fax: +254-11-486473; Home: 474582; 0733-851656
Email: dobura at africaonline.co.ke Web: http://www.cordio.org

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