Wrecked. Day 3. Part 3.  Great Keppel Island, April 2024

According to the Bureau of Meteorology, it was going to storm on Sunday.  Instead, the day broke calm and sunny.   And so, Jenn (not me, there is another one) and M-J from Keppel Dive, took a few of us around to the very exposed Wreck Beach facing due east.   This is the beach where you can get properly wrecked on Great Keppel Island – as the story goes.

The map at the dive shop, and me.

According to local legends there is gold there, buried somewhere in the sand with a shipwreck, or three.

I found gold by way of a nudibranch, specifically Chromodoris kuiteri.

The tail end of a nudibranch with filaments of gold. Photograph by Jenn Marohasy at Wreck reef on Sunday, April 21.
Can you see the nudi, amongst the corals?

Most striking when you drop down to the reef at the northern end of the bay is all the bleaching.   It is everywhere on this island.

There is so much bleached coral along the wall that we swam from the beach east, northern end. Wreck Beach reef, Sunday April 21.

What is not bleached seems to be a particularly dark chocolate brown:  it seems much of the coral either has no zooxanthellae or too much.

Plate corals a very dark brown replete with zooxanthellae, contrasted against the stark white branching that is bleached.
Contrasting bleached versus dark brown corals, but these perhaps brown from algae rather than symbiotic algae.
What species of coral is this? It looks a healthy brown with purple tips. Wreck Beach reef, April 21, 2024.

Can someone explain to me how this works, how does the zooxanthellae become toxic to the coral when the water become too warm? Why is the physical mechanism?

I’m told that it is not a case of the zooxanthellae dying insitu, rather the coral polyps kick them out.

Leaving Wreck Beach reef, for Secret Cove. More about this secret and a shark in Part 4, tomorrow.
Trying to remember the name of this fish. There were a lot of them here, and around the headland at Secret Cove.

via Jennifer Marohasy

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April 21, 2024 at 10:38PM

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