When white syndrome, sweeps through a colony of plating Acropora, it doesn’t hang about. White syndrome is a deadly coral disease that rapidly kills the coral polyps, exposing the underlying coral skeleton, often leading to the death of the whole colony. It is a contagious disease and quite distinct from coral bleaching; it is caused by pathogens, including bacteria, and can result in significant reef decline by completely destroying coral tissue, leaving a white, denuded skeleton. It is thought to be caused by poor water quality.
At the beginning of December 2021, I photographed an area of the reef where the disease was starting to nibble away at the edges. You can see a patch of this area in the first photograph. Within weeks that patch and most of the rest of that area was dead. White syndrome had swept through leaving behind white skeletons – all the coral polyps inside, gone. Dead.
By January 2023, the skeleton was covered by an opportunistic growth of slimy green algae, smothering it and crowding out the recruitment of new baby corals that might have been able to grow there. You can see this in the second photograph.
Fast-forward to the end of August 2025, getting on for four years later, and, of course, and at risk of stating the obvious, it’s still dead. No new coral has begun to grow apart from one glimmer of hope – a tiny new nub of coral peeking out in one corner. The skeleton is still covered in algae, but this time it’s grape caulerpa taking over. A tough little sea squirt community has moved in, too, coating big patches of the old Acropora plate.
To help you compare the three photos, I have marked the same small Pocillopora coral on each with a red circle. In the third image I have similarly marked the area of new coral growth.
The point is how fast the death happens, and how agonisingly slow recovery can be. In just over a month, a vibrant colony was wiped out. Nearly four years later, it’s still stuck in the algae–ascidian stage, with only the faintest hint of new growth.
And here’s the kicker. December 2021 was at the beginning of Norfolk Island’s wettest year since records began back in 1891. Then 2024 turned out to be one of the driest. In 2024, with little runoff, we barely saw new cases of white syndrome. The surviving corals across the lagoon began to pick up with new growth. Things were looking great.
However, since April this year (2025) we’ve already clocked up 965 mm of rain – well above the historical average. Now the rain’s back, and, bit by bit, so is the disease. That is because nothing has changed in the meantime to fix the poor water quality flowing into the bay, so of course the corals are copping it all over again. Coral researchers call this process the slippery slope to slime. Or a ‘phase shift’ where a coral reef turns from being dominated by coral to being dominated by algae. That is exactly what we could be witnessing here on Norfolk Island.
It’s a stark reminder: without tackling the root cause, we’re just watching the same sad story repeat itself.
4 December 2021. I first photographed this area just as white syndrome began to take hold. When compared to the images below, it gives you a good idea of what was once there and what we have lost.
20 January 2023. The dead coral skeleton is covered in green algal slime.
22 August 2025. The bottom circle marks a nub of new coral growth. The silvery white areas are covered with colonial ascidians (sea squirts).