Fiji bleaching event
Biological Consultants (Fiji)
lovell at suva.is.com.fj
Mon Apr 10 15:26:23 EDT 2000
In addition to Bruce Carlsons reports, the following is a more general
appraisal of the coral bleaching event now developing in Fiji.
March/April Coral Bleaching Event in Fiji April 10, 2000
A coral a bleaching event is well underway in Fiji with 30-31C temperatures
being experienced along the southern areas of Fiji's main islands of Viti
Levu and Vanua Levu. Considering the time-line of this warm water event, the
first reports of minor bleaching were reported in late April. An observation
(Feb. 20, 2000) of some minor bleaching at the entrance to Suva Harbour was
interpreted as due to heavy rain. I conducted a Reef Check at the Fijian
Resort (27/2/00) at the western end of the Coral Coast, S. Viti Levu and saw
only minor, "possible" bleaching in a few colonies of Acropora. It was
determined then that no bleaching was occurring. A recent call to the Fijian
Resort Dive operation confirmed that the bleaching has occurred in the area
of survey within the first week of March. Austin Bowden-Kerby commenting the
reef flat environment gave the following report. "The Cuvu reefs (Fijian
Resort) are pretty severely bleached, it started over a month ago, but has
spread. The interesting thing is what has not bleached; most of the larger
colonies appear completely unaffected, adapted to the heat, regardless of
species. Also smaller Seriatopora and some Pocillopora are resistant as
well as many of the staghorn Acroporas. There has been some death, but lots
of extremely bleached corals seem to be holding their own so far, many
Stylophora look like they might die though." By contrast, it is the larger
colonies that appear to be affected in the subtidal areas of the reef slope.
The bleaching of large plate and corymbose Acropora colonies are evident.
A trip to Frigate Pass in the Beqa Lagoon (12/3/00) revealed extensive
bleaching, or should, I say bluing or yellowing. The effect was dramatic
with sprawling colonies of Acropora monticulosa and A. humilis appearing
bright blue due to the absence of the zooxanthellae. A. nana also exhibited
a blue appearance. A. hyacinthus, A. clathrata, A. nasuta, a sprawling
zoanthid and many soft corals took on a yellow appearance. Some became very
white. Light green was a common color for Gonioporas. Regardless of color,
it often appears luminescent. It is estimated that there is 50% bleaching
with >65% in some areas. Up to 30% of those affected were blue. Montastrea
curta and Platygyra sinensis were affected. A. muricata was bleaching
white. Pocillopora eydouxi is common and showed no bleaching. The presence
of the bleaching was patchy with some areas not particularly affected. This
observation was probably two weeks into the event.
Now a little more than a month the beginning of the event, a dive on the
local Suva reefs near the harbour entrance, and Rattail Passage (2/4/00)
revealed extensive bleaching with an estimate 75% of the hard and soft coral
affected. Most of these were bleached white though many still had blue,
pink or yellow coloration. Unfortunately, an estimated 15% of colonies had
algae beginning to grow on their surfaces, indicating that these were the
colonies affected early in the episode (~1 month) and have died. Many of
the colonies were ½ bleached indicating a progressive effect with some
portions covered by algae. The water temperature was 31.5C at the Suva
Harbour entrance and 31C at Rattail passage.
Interestingly, some species that were bleached totally, have colonies of the
same species nearby that appear to be totally unaffected. The bleaching was
evident at depth and in underhangs and crevice areas. A listing of the
species that have bleached is extensive, with many Acroporas and notably
colonies of Lobophyllia sp. and Diploastrea sp. All of the Montiporas seemed
affected. Some Acroporas like were completely unbleached. Unlike the
earlier observations at the Fijian Resort, the Seriatopora and Pocillopora
are bleaching to varying degrees. Large tabulate colonies have been affected
often progressively. In some cases algae has began to settle on one portion
of the colony which is bleached white in the center but will still exhibit
natural coloration on a portion. Among the bleached colonies, there are
colonies that are not bleached and appear healthy.
Other observations have come from the Cousteau Resort near Savusavu, Vanua
Levu which report high percentages of coral bleaching (65%) (11/3/00).
Reports of from helicopter trip along the southern coast of Viti Levu
revealed the bleaching to be occurring all along the coast.
Two things have surprised me about this event. One is the vivid colour of
many of the corals (pinks, blues and yellows) which are evident after the
expulsion of the their zooxanthellae. It also seems that the symptom of
coloration is more characteristics of the offshore, clearer waters. In the
inshore areas, the bleaching white is more apparent, but many exceptions.
The second is the rapid nature of the effect. One week all is well and the
next week, there is apparent widespread bleaching.
We are now in the sixth week with high water temperatures. NOAA's hotspot
website seems to be very informative in showing the progressive warming. Of
interest, the warm water didn't migrate from somewhere else. It originated
at these latitudes, largely south of Fiji extending east. Thankfully,
according to the website, it seems to be breaking up, at least near Fiji.
Temperature reports from some areas confirm that the inshore temperatures
still remain high (~31C).
A call to Ha'atafu, Tongatapu, Tonga and the report of the widespread bluing
of coral is the same. As with Fiji, lots of blue and yellow coloration is
characterizing the coral areas. A trip 10 miles north of Tongatapu to some
isolated barrier reefs revealed the same phenomenon. Bleaching has been
reported from the Ha'apai group, central Tonga. Though further north and
outside of the hotspot area, bleaching of the large Acropora plates,
particularly evident at depth (~15m), has been reported from Guadalcanal,
Solomon Islands. The extent is uncertain but is occurring. Apparently less
so in the shallow waters.
Biological Consultants, Fiji
Edward R. Lovell
More information about the Coral-list-old