No Subject

JKoven at JKoven at
Tue Aug 29 16:11:09 EDT 2000

The corals on Fiji’s Astrolabe Reefs appear to have fared somewhat better 
during the widespread bleaching event reported on by Dick Murphy, Ed Lovell 
and Bruce Carlson.  Half of all specimens counted there were alive and 
unbleached a month after the SST’s had lowered.  I suggest that this is due 
to fewer anthropogenic influences (inhabitants of the islands within the 
lagoon are counted in hundreds, not thousands) and their location amid ocean 
currents unmitigated by any large land mass. Except for the area around 
Kadavu, the only high island, there is not a lot of fresh water run-off into 
the lagoon and there are virtually no farm-based nutrients.

It does not explain why often 1 of 2 or more specimens of the same species 
occurring side by side was bleached and the other not.  

In late May and early June I assessed the extent of coral bleaching on the 
Great and North Astrolabe Reefs in Fiji.  The northern most parts of these 
reefs are located 30 -35 NM south of Suva, below the Beqa reefs but still 
well within the range of the higher SST’s that occurred from Feb-April.

The survey included sites inside the lagoon and relatively close to the 
inhabited Dravuni Island as well as those outside the reefs and at a remote 
windward corner of the North Reef which is rarely visited/fished.

General observations:
As reported by others, most of the bleaching was within the first 25 M 
although there were some very large completely bleached specimens of 
Montastrea and Montipora near the first bench at 27 M, on the leeward side.  
Some very large (3-4 M high and wide) Porites colonies in alleys behind the 
outer reef pinnacles were bleached.  Bleaching was rare between 27 and 40 M 
and almost non-existant below that.
34% of the corals in the lagoon of the Great Astrolabe Reef were bleached - 
17% had died recently and were already covered by blue-green algae.
26% of corals on the leeward side of the GAR and windward on the North Reef 
were currently bleached with another 20% recently dead.

Among the Acropora 16% of those in the lagoon were bleached but 33% had died 
recently and were over-grown by blue-greens.   As Bruce Carlson reported, the 
smaller specimens (>10 cm) were unaffected. Some of the large Acropora 
robusta and formosa specimens in the lagoon exhibited the “shade effect” 
mentioned by Bruce with the underside of branches appearing normal, the 
upperside bleached.  Only 9% of Acroporids outside the lagoon were bleached 
but 28% had died recently.  

The Seriatopora were almost entirely wiped out - in 60 dives I saw only one 
live specimen.  On the survey sites all of them had bleached, died and been 
covered by blue-greens.  Stylenocoellia and Symphyllia., both with a small 
number of representatives, were either bleached or dead at these sites, 
but.were seen live elsewhere.

Whereas in the past I had seen Millepora move in after the death of other 
corals, with bleaching their representation has been cut by nearly 65%. 

43% of the Halimetra pileus specimens at a deep lagoon site were a brilliant 
fluorescent yellow with another 31% bleached or partially bleached.     

The normally hardy Diploastrea was never seen completely bleached but often 
bore a mottled appearance.  In one case the outer 10 cm rim of a large colony 
was completely white.  Lobophyllia colonies were also often mottled with 
individual corallites being bleached, completely unbleached or somewhere in 

Sinularia and Sarcophyton were almost all bleached, as were many anemone.  

Least affected were Achrelia, Anacropora, Euphyllia, Goniastrea, 
Goniopora/Alveopora, Pectinia, Turbinaria, Tubastrea.

There was an outbreak of Acanthaster plancii on the crest of the North 
Astrolabe Reef with 35 specimens in one 300 square meter area along the crest 
- I have never seen that many in all of 12 years on these reefs.  Although 
they were not that numerous in other areas of the reef this yar, there were 
more than ever seen before.  

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