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 3 – A reef in decline
22 December 2024, showing the extent of the disease on a photo taken on 23 March 2025 (see right)
23 March 2025
The examples I’m sharing today may appear small – tiny patches within individual colonies – but the processes they illustrate scale up across the entire ecosystem. Repeated again and again, these localised disease outbreaks accumulate into widespread reef degradation. Today’s images document the progression of Atramentous Necrosis, a bacterial disease, as it spreads across Montipora coral colonies on Norfolk Island’s reef.
I write about this disease in a blog post, here: Combine bacteria, fungi, and maybe a sponge = one toxic mess.
Disease emergence during dry conditions
The images, above, were taken in December 2024 and March 2025, during an extended dry period. In these images, the advancing tissue loss caused by Atramentous Necrosis is clearly visible. Yet if you were to snorkel past this site today, the past outbreak would be difficult to detect – the dead coral skeleton is now largely obscured by a film of algae. The damage persists, but it has shifted out of immediate view.
Throughout the drought of 2024, overall disease levels on the reef declined significantly. However, this first example demonstrates that even in relatively favourable conditions, a low level of disease persists within the ecosystem – a reservoir waiting to resurge when conditions once again become favourable for outbreaks (Page et al., 2023).
Long-term impacts and reef resilience
The second example, shown below, shows another Montipora colony, first photographed in January 2024, following high disease prevalence during a prolonged wet period through 2022 and 2023. While the central area affected by Atramentous Necrosis remains dead, the surrounding healthy coral has grown well during the drier months of 2024. This highlights both the vulnerability and the resilience of coral reefs: when water quality improves, surviving colonies can recover and regrow – but previous damage remains as a legacy.
Residual disease remains in the system
It is important to remember that Norfolk Island’s reef has experienced exceptionally high levels of disease. As noted by Page et al. (2023), ‘In December 2020 and April 2021, we observed 60% of surveyed Montiporid coral colonies with signs of disease, a prevalence in line with the most severe coral disease outbreaks recorded to date worldwide.’ That history underscores both the fragility of this system and the scale of recovery required when outbreaks occur.
13 January 2024
22 May 2025
About Atramentous Necrosis*
Multifocal to irregular pattern of tissue loss exposing bare, white skeleton subsequently colonized by a distinctive grayish-black, fouling community.
Lesions typically start as small bleached spots followed by tissue loss and coalescence of adjacent lesions.
Bare skeleton may be covered by a thin white film, under which a black sulfurous deposit may accumulate, giving the lesion a grayish appearance.
Chronic infections result in colonization by epibionts which obscure typical signs of disease.
Montipora are most susceptible, but it has also been observed on Acropora, Echinopora, Turbinaria and Merulina.
*Quoted from the Coral Disease Handbook: Guidelines for Assessment, Monitoring and Management.
References
Page, C. E., Leggat, W., Egan, S., & Ainsworth, T. D. (2023). A coral disease outbreak highlights vulnerability of remote high-latitude lagoons to global and local stressors. iScience, 26(3), 106205–106205. https://doi.org/10.1016/j.isci.2023.106205