Stark White – Fields of Bleached Acropora, Great Keppel Island


Scuba tank on my back, I rolled backwards off the Keppel Dive boat at Bald Rock reef yesterday into the ocean.  I was hoping that as with previous claims of mass bleaching, this was exaggerated.

Bald rock, and the Keppel Dive shop boat.

The New York Times had featured corals from Great Keppel Island in a single photograph as badly bleached.  The image showed pale corals not white corals, and from one photograph it is difficult to know the extent.

Visibility was not great, but as I descended down into the blue, I could start to see white: by 8 metres I could see a large field of properly bleached Acropora, and that was all I could see, and the fishes.  I could not see any healthy corals.

Fields of badly bleached Acropora, Bald rock Reef, April 19, 2024.

I spent 45 minutes under-the-water at this dive site to the east of Great Keppel Island and I have never seen so much stark white, badly bleached coral.

The reports of bleach here have not been exaggerated.  This is a really badly bleached coral reef.

My buddies on scuba had dived here through summer and said it was whiter back eight weeks ago; the bleaching had apparently come on suddenly mid-February.   And, they said, to their eye, some of the corals were starting to get their colour back as the water had cooled down by several degrees.

It was possible to find corals at this site with some zooxanthellae, as we swam to the east along the wall.

I could also see sections of this reef already beginning to die, that the algae have already set in.

According to Alison Jones’s book about the Keppel Island reefs:

In the shallow waters of Keppel Bay, coral bleaching on a mass scale has been infrequent and reef recovery has usually been fast.

Mass bleaching was recorded in Keppel Bay in 1998, 2002, 2006, 2020, with minor bleaching in between.  There are also earlier unofficial reports by local fishermen of bleaching in 1983 and 1987.”

She also writes that:

Keppel Bay’s reefs can recover rapidly from bleaching because of the excellent growth rates of this branching species.  After the catastrophic 2002 bleaching episode, coral cover increased rapidly, reaching 81 percent in 2004, the highest coral cover ever documented.”

Of course, bleaching has occurred over the millennia. It is just that scuba, and more specifically underwater photography, is a recent technology and the politicisation of corals even more recent.

This is a colour lithograph painted in 1862, showing a section of bleached coral reef in the Red Sea. More information, https://km.dmcr.go.th/ckeditor/upload/files/Research%20Bulletin/FullpaperPMBC/06Coral_bleaching_recorded_durin.pdf

Despite all the white, there was an abundance of little fishes, and so many other creatures including sting rays, nudibranchs, turtles and from the dive boat as we approached this reef from the north, I saw a dolphin.

A nudibranch climbing between healthy and algae, at Bald rock reef, April 19, 2024
The red arrow shows the same nudibranch, with more reef, for context.
The red arrow shows the same nudibranch, and this wider shot includes some of the very stark, very white branching corals. All the photographs in this post were taken by me/Jennifer Marohasy at Bald rock reef yesterday, April 19, 2024.

 

So much thanks to Jenn and the rest of the crew at Keppel Dive for making these reefs that will recover, so accessible to those of us who are curious, https://greatkeppelwatersports.com.au



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By GIL