• Home
    • Algae
    • Corals
    • Eels
    • Everything Else
    • Kingston, Norfolk Island
    • Nudibranchs, Sea Slugs and Flatworms
    • Octopuses
    • Out On A Swim Index
    • Reef Fish
    • Sharks
    • Sea Anemones
    • Sea Stars
    • Sea Urchins and Sea Cucumbers
    • Turtles
    • Underwater
    • Videos
  • Out on a swim - blog
  • About
  • Contact + Subscribe
Menu

Norfolk Island's Reef

Discover a fragile paradise – Norfolk Island's beaches, lagoons and coral reef
  • Home
  • Explore
    • Algae
    • Corals
    • Eels
    • Everything Else
    • Kingston, Norfolk Island
    • Nudibranchs, Sea Slugs and Flatworms
    • Octopuses
    • Out On A Swim Index
    • Reef Fish
    • Sharks
    • Sea Anemones
    • Sea Stars
    • Sea Urchins and Sea Cucumbers
    • Turtles
    • Underwater
    • Videos
  • Out on a swim - blog
  • About
  • Contact + Subscribe

Out on A Swim

‘Out on a swim’ is a coral reef blog that tells the stories of the characters who live under the waves and what has caught my eye when ‘out on a swim’ in the lagoons of Norfolk Island. It is also a record of the difficulties Norfolk Island’s reef faces, like many others around the world, as a result of the poor water quality that has been allowed to flow onto it.

This page shows the most recent blog posts. For the complete catalogue, visit the ‘Out on a swim index’ page.

This blog is rated in the Top 20 Coral Reef Blogs in the world.

No results found

The colony in 2025, showing the vivid green colour when healthy (and the surface texture I’m hoping will eventually support a confident ID)

The lime-green coral in Slaughter Bay – a 40-year paper trail

May 17, 2026

Some reef stories start underwater. This one started in a filing cabinet in a little-used back office.

While searching through the Norfolk Island National Park archives as part of my PhD research, I found a loose, rough hand-drawn mud map marking the location of a coral colony in Slaughter Bay. It was drawn on the back of a scrap of reused paper (as was common at the time) and the printed text on the reverse was dated 20 November 1988. I immediate;y knew exactly which coral it was pointing to.

The map drawn on scrap paper by Dr Fred Brook, c1989, intrigued me and got me coral sleuthing

The reverse side of the scrap of paper had this date, 20 November 1988

I’ve been photographing this colony for years, and it is the only one of its species I have found in the Kingston Lagoon. In my own files it’s called ‘Green Mountain’ (I have some odd names for some of my locations, but they make sense to me) – not because it’s huge, but because it’s so unmistakable. There’s nothing else quite like it. Since 20 February 2020 I’ve regularly taken photographs of it at random opportunistic times as I’ve passed. Norfolk Island resident and snorkeller Betty Matthews kindly went through her archive too and found some older photos from 2018 to add to the record. Over that period its fortunes have waxed and waned. I’ve seen it look stressed and diseased, I’ve seen it smothered in algae, I’ve seen it recover, and I’ve watched it appear to shrink and expand over time.

I assumed the mud map was simply ‘from 1988–1989-ish’, but still, it intrigued me that someone nearly forty or so years ago had found this coral colony equally noteworthy as I have done.

It has taken a little while, but I’ve now found the story behind this map. It’s fascinating.

On an unrelated matter, I contacted Dr Fred Brook, a now-retired geologist – who had accompanied ichthyologist (fish expert) Dr Malcolm Francis on his 1989 visit to Norfolk Island to undertake a fish census. While here, Brook had also recorded corals in the Kingston Lagoon, so I was interested to know if he had kept any notes other than the report that had been produced subsequent to their visit. In his offical report he’d listed this colony as Astreopora moretonensis. As an addendum to my email, I included the mud map and asked, by the by, if he were familiar with this colony. It turned out that not only was he familiar, but he’d been the artist who had thoughtfully drawn the map!

The name ascribed to this coral, Astreopora moretonensis, was a clue – not because it neatly solves the ID problem (because it likely doesn’t), but because it ties the coral to a much older observation.

Brook’s coral list from his visit refers back to Veron and Wallace (1984), in which Astreopora moretonensis is noted as rare at Norfolk Island: ‘one large encrusting colony … at the west end of Slaughter Bay’. In other words: this was already being singled out as a one-off colony back in 1984.

Two extracts from a scanned hard copy, and later annotated, of Brook’s appendix on the ‘Geological origin and coral fauna of Kingston Lagoon’ … (Francis et al., 1990, Appendix 5).

But it was this line that made me stop. Hand written in pen on the same list, which I also found in the archives, is a simple update: ‘this colony is still thriving – 30/3/92’.

So now, instead of guessing when this coral might have established, we have something better: a paper trail. Listed as a single colony in 1984. Mapped again in 1989. Confirmed as ‘still thriving’ in 1992. And still present today.

Why monitoring reefs is important

One thing I have been surprised at is how much and how quickly reefs can change. They don’t sit still. Sometimes you can only see the pattern when you’ve made enough repeat visits to look back properly.

The Coral Sea Foundation put it this way, ‘tropical coral reefs are among the most rapidly changing ecosystems on Earth’, which is why ‘rigorous monitoring programs, adequately replicated in space and time’ are needed. They also argue that money could be better spent on monitoring (and strong protection) rather than on small restoration experiments that make us feel busy but don’t always shift the dial.

That’s the lens I’m looking through here. Since 2020, Australian Marine Parks, Temperate East Zone, has backed a coral health monitoring program in the lagoon with a team of coral health researchers. That kind of long, repeated, same-sites monitoring is how you build a baseline. And without a baseline, we are just arguing from anecdotal impressions.

It also gives context to what I’ve seen at Green Mountain since 2020. This colony hasn’t been thriving every day of the last forty years. My photos suggest it has gone through some rough patches. But it has persisted – through decades of seasons, stress, and whatever else the lagoon has thrown at it.

View fullsize December 2018 (B. Matthews)
December 2018 (B. Matthews)
View fullsize 20 March 2020
20 March 2020
View fullsize 22 September 2020
22 September 2020
View fullsize 8 February 2021
8 February 2021
View fullsize 20 July 2023
20 July 2023
View fullsize 23 December 2023
23 December 2023
View fullsize 2 July 2024
2 July 2024
View fullsize 3 July 2025
3 July 2025
View fullsize 29 November 2025
29 November 2025

Above are just a few photos from a complete series, beginning with Betty Matthews’s image taken in 2018, then mine from March 2020 on. It is interesting to note that the colony looked a great deal healthier during the drought that occurred in the second half of 2023 and into 2024.

My most recent photo of Green Mountain, 13 May 2026

The identification problem

I’ve tried to obtain a confident ID for ‘Green Mountain’, without success. The archive uses the name Astreopora moretonensis, and Corals of the World lists that species with Veron and Wallace (1984) as the taxonomic reference. Taxonomic databases also recognise A. moretonensis as an accepted species name. But identification from photos alone is notoriously tricky with some corals, and colour is not a reliable diagnostic feature. So for now, I’m treating the archive label as exactly what it is – an historically recorded identification – rather than something I can independently confirm from images.

A request to locals

If you’re a long-term local and you remember this standout green coral at the west end of Slaughter Bay – I’d genuinely like to hear from you. Even better: if you (or your family) have old lagoon photos tucked away in albums, I’d love to see them. Stories are valuable, but dated photos are gold.

Why I’m writing this

Partly because it’s a good story. Partly because it’s rare to be able to pin anything living in the lagoon to an anchored timeline like this. And partly because reef history doesn’t only get told in scientific papers; sometimes it sits in drawers – in hurriedly drawn mud maps, species lists, and in the marginalia of handwritten notes that somebody bothered to add in the moment. That’s the bit I love the most.


References

Francis, M. P., Brook, F. J., Randall, J. E., Cole, R., Williams, M. W., Ward, C., & Davis, M. (1990). Norfolk Island fish survey 11–26 November 1989 (Unpublished report prepared for the Australian National Parks and Wildlife Service).

In Corals Tags corals, coral reef, Norfolk Island, Taxonomy, coral species
What Norfolk Island’s reef tells us about environmental blind spots →
Featured
The lime-green coral in Slaughter Bay – a 40-year paper trail
May 17, 2026
The lime-green coral in Slaughter Bay – a 40-year paper trail
May 17, 2026

Green Mountain – the name I give this coral in my database – is a coral I’ve photographed for years as I swim past. Then I found its backstory in the Norfolk Island National Parks archives: a rough map, reused paper, a note in the margin – ‘still thriving’. That’s how baselines begin.

May 17, 2026
What Norfolk Island’s reef tells us about environmental blind spots
Apr 5, 2026
What Norfolk Island’s reef tells us about environmental blind spots
Apr 5, 2026

The Kingston dredging proposal on Norfolk Island raises a bigger question than dredging alone: how well do standard environmental assessment tools capture the real significance of a remote and unusual reef system like Norfolk Island’s?

Apr 5, 2026
Hammer coral time!
Mar 30, 2026
Hammer coral time!
Mar 30, 2026

Hammer corals have unique tentacles that are large, fleshy, and tubular; these terminate in a ‘T’-shaped, hammer-head or anchor. Beneath all these softly waving tentacles is an extraordinary skeleton structure, which helps define them as a large polyp stony coral.

Mar 30, 2026
Norfolk Island’s fishes: drifters, residents and the ones still missing
Mar 24, 2026
Norfolk Island’s fishes: drifters, residents and the ones still missing
Mar 24, 2026

Norfolk Island’s fish fauna reflects both connection and isolation. Some species may arrive from elsewhere as drifting larvae, some populations appear to persist locally, and some fishes known from islands on either side of Norfolk have still not been recorded here. This post looks at what old survey work, regional checklists and genetic studies suggest about that more complicated picture.

Mar 24, 2026
18 Jun 2025 (20)_crop.jpg
Mar 7, 2026
Alveopora or flowerpot coral – how to tell the difference
Mar 7, 2026

They look alike at first glance, but Alveopora and flowerpot corals are not the same. The easiest way to tell them apart is to count the tentacles.

Mar 7, 2026
Norfolk’s lagoonal reef – the 2025 report, in plain English
Feb 27, 2026
Norfolk’s lagoonal reef – the 2025 report, in plain English
Feb 27, 2026

We now have the 2025 Norfolk Island reef health report, so I’m taking the opportunity to translate it into plain English here. Sadly, it’s more of the same story in Emily and Slaughter Bays – a reef that can cope with some stress, but is being asked to cope with too much, too often.

Feb 27, 2026
Halimeda’s night shift – why this reef algae changes colour
Feb 20, 2026
Halimeda’s night shift – why this reef algae changes colour
Feb 20, 2026

Halimeda is a calcareous green reef alga that forms new segments overnight, shifts from white to bright green by dawn, then pales again as calcification begins. A quick look at one of the reef’s smartest algae.

Feb 20, 2026
Reef real estate – a bubble-tip’s six-year stand-off
Jan 11, 2026
Reef real estate – a bubble-tip’s six-year stand-off
Jan 11, 2026

Reef space is finite, and nothing ‘shares’ it politely. This short photo essay follows one bubble-tip anemone on Norfolk Island’s lagoonal reef as it holds a crater surrounded by Montipora. The coral builds a rim; the anemone holds the centre. Six years apart, and the argument continues.

Jan 11, 2026
A year in review – 2025 on Norfolk Island's reef
Dec 28, 2025
A year in review – 2025 on Norfolk Island's reef
Dec 28, 2025

Norfolk Island’s reef in 2025 – a year in review. From NOAA bleaching alerts and the UN Ocean Conference ‘Warning Signs’ series to post-drought coral recovery and a wet winter revealed in long-term rainfall records, this post captures the wins, losses, and shifting baselines beneath the lagoon. Includes reef photos, highlights from Reef Relief, and standout stories from 2025 – from coral health and disease to boxfish biomimicry, sea urchins, nudibranchs, and heat-stress signals in anemones.

Dec 28, 2025
Herbicides, heritage, and an inshore reef: what happens when land management meets lagoon health
Dec 15, 2025
Herbicides, heritage, and an inshore reef: what happens when land management meets lagoon health
Dec 15, 2025

Herbicide use near Emily, Slaughter and Cemetery Bays raises questions about inshore reef health, heritage land management, and environmental protection on Norfolk Island.

Dec 15, 2025

Latest Posts

© 2026 All rights reserved.