As the UN Ocean Conference convenes in Nice, France from 9–13 June 2025, global delegates are grappling with the mounting pressures facing the world’s oceans – habitat degradation, pollution, biodiversity loss, and the destabilising impacts of climate change.
On the opposite side of the world, Norfolk Island – a tiny Australian external territory – offers an uncomfortable preview of what is unfolding elsewhere. Our small inshore coral reef lagoon is, in effect, an early warning system: small enough to observe detailed changes, and simple enough to trace many of the drivers of degradation with clarity.
Here, disease outbreaks, growth anomalies (coral ‘cancers’), declining water quality, and nutrient-driven algal blooms are progressively dismantling the reef’s ecological structure – much as they are elsewhere, but on a scale that makes the processes starkly visible. Years of neglect, deferred decisions, and unmanaged land-based runoff have contributed directly to the poor water quality now driving these changes. Norfolk’s reef shows us not only what is happening, but how quickly these shifts can occur when stressors are left unchecked.
This week, alongside the global discussions in Nice, I will post a daily series of photographs and observations documenting these changes as they have unfolded over the past five and a half years. Norfolk Island’s reef may be small, but it is a living case study – a microcosm of what many other coastal ecosystems may soon face unless serious, funded interventions are made.
The warning signs are already here. The question is whether we choose to act.
Day 4 – White Syndrome on Hydnophora pilosa: a Fast moving shadow
This coral colony lives right in the channel that connects Emily and Slaughter Bays on Norfolk Island – a spot where I often pause during my swims to admire the group of large Hydnophora pilosa growing there.
On 23 November 2023, I noticed something unusual on one of them – a bright white patch where healthy tissue had recently died. It was the start of a white syndrome outbreak. Over the next few weeks, I kept going back to check in and take photos, watching as the disease gradually spread. Within a short time, about a quarter of the colony was affected.
The photos in today’s post show how it unfolded: the infection spreads, the coral loses tissue, and eventually algae moves in and takes over.
White syndrome doesn’t bleach coral – it kills it outright, stripping the tissue off and leaving just the skeleton. And once that happens, algae moves in fast. By mid-2024, you could already see turf and macroalgae settling in. By June 2025, the whole area was fully overgrown – no sign of coral coming back.
This is what we mean by a phase shift – when coral dies and algae takes over. It’s not a one-off. It’s happening all over the reef.
On a healthy reef, this coral might have stood a chance of partial recovery. But with nutrient levels still high, algal growth is favoured over coral recruitment. Once algae gains a foothold, it’s incredibly difficult for juvenile corals to re-establish.
The result? A coral that was once thriving is now scarred and covered in algae.
Fish behaviour: opportunistic grazers
Interestingly, I also observed multispine damselfish (Neoglyphidodon polyacanthus) and banded scalyfins (Parma polylepis) nibbling around the lesion edges as the disease advanced (see the photos, below). This behaviour is opportunistic – they aren’t the cause of the disease, but they take advantage of the exposed polyps and weakened tissue.
