Reefer gladness. Wonderful Aussie science from the top end.

To celebrate National Science Week, NerdNews is shining a light on a team of marine scientists and traditional custodians for the work they have done in exploring these precious places.

(First published on my Substack where you can get #NerdNews, marvellous maths and general geekery.)

(All images courtesy Dr Hadley England UTS)

A reef off the radar.

You’d need to be living, I don’t know, deep under the sea, to not have noticed the news that Australia’s reefs are in a parlous state.

But the phenomenal Great Barrier Reef, understandably, gets most of the attention.

These living coral reefs in the Gulf of Carpentaria first turned up in the scientific literature in 2004.

And they aren’t tiny. Satellite imagery now suggests the reef system could cover more than 3,200 square kilometres, though no official estimate exists.

In the two decades since that first mention, seven papers have been published on reefs in the region. Groote Eylandt, the biggest island in the Gulf, didn’t rate a mention in any of them, and nor did corals.

Cue the Anindilyakwa people. They have cared for and lived off the Gulf’s waters for thousands of years and, as such, hold detailed knowledge of the reef systems.

But until now, what did not exist was a formal scientific record of what is on the seafloor. This is what conservation managers need before they can argue for anything.

A study published in PLOS One on 12 August has now produced one.

One ranger, who has seen the GBR and Ningaloo, is clearly impressed.

“I truly believe I’ve seen the most impressive array of marine life.” — Annabelle Doheny, Anindilyakwa Land and Sea Rangers.

Stingers be damned.

While our northern seas are gorgeous, they can also be nasty. Not the seas per se as much as the saltwater crocodiles, box jellyfish and stingers that call the waters around Groote Eylandt home.

Not surprisingly, this limits what a human diver can do. So the team used a BlueROV2 remotely operated vehicle with a GoPro strapped underneath.

Five reef sites in the north of the archipelago were surveyed over four days in June 2024. Those sites were handpicked by local Anindilyakwa Rangers based on traditional knowledge and the cultural significance of the sites.

To make this an ongoing project, rangers were trained to pilot the ROV and drones. This means the monitoring can continue without the university.

Say cheese.

Ok so what did the ROV images tell the team? In short, the data told a complex, important story.

(All images courtesy Dr Hadley England UTS)

Across the five sites, the amount of hard coral varied. As little as 5.2% at one site, up to 47.1% at the richest. Unfortunately not all of that coral was thriving and healthy. At the least affected site, dead coral made up 10.8% of the total coral cover. At the worst hit site, it was 80%.

And it came in all sorts of shapes. Branching corals, tabulate, massive, sub-massive, encrusting, digitate, and corymbose. Hey, how good are coral names!

And the shapes of the coral really matter. The right coral can create habitats for fish, which are vital for locals who live off the water. For that you need the fragile branching and tabulate corals and, basically, more structure means more and bigger fish.

Unfortunately, branching corals were scarce. Tabulate corals were missing entirely from three of the five sites, and at one of those, encrusting corals were the dominant form, along with that awful 80% of coral dead.

Massive corals dominated three of the five sites. They’re still habitat, but nothing like the structure you get from branching and tabulate corals. So while many of the images of the reef show, in places, lots of coral, coral cover alone doesn’t tell you how the reef is doing.

Scientists call reefs like these marginal. They are not terminally damaged, but growing right at the edge of what corals can cope with. We are talking murky water, sediment, big temperature swings, sluggish flow. A whole host of things that I can only imagine suck if you are coral. It can create the confusing illusion of a reef that appears coral-rich but is actually under real pressure.

This leaves a crucial question. Were the fragile corals never there, or did they go in the bleaching in February, or in Cyclone Megan in March? Dead branching skeletons were still standing with their structure intact, so at least some of the losses look recent. But with no earlier survey to compare against, nobody can say how much was the heat, how much was the cyclone, or what the reef looked like before either.

Son of a bleach!

In February 2024, rangers on routine fieldwork found widespread bleaching. They were not equipped for formal surveys, so they took 67 photographs. Later analysis put 62.3 per cent of the photographed colonies in the two most severe categories of the CoralWatch index. Giant clams were bleaching too.

The bleaching data is concerning, but not for the reason you might expect. Heat stress on reefs is measured in Degree Heating Weeks. Below 4.0, reef-wide bleaching is generally not expected. Widespread mortality is not expected until 8.0. Satellite data for these sites topped out at 2.10, which puts them in the mildest “Bleaching Warning” category.

The reefs bleached anyway. The authors describe this as the first known instance of mass coral bleaching in the Gulf of Carpentaria. This is bad news for the comfortable assumption that reefs already doing it tough must handle heat better.

“Only monitoring can show what’s actually happening on the reef.” — Dane Wattle, UTS.

It is important to stress that this is not a longitudinal study, but a one-off descriptive snapshot. It is a baseline for future research, but it must be noted it was taken four months after the bleaching, three months after a cyclone. The authors are clear that it may not represent a healthy reef.

The moral of the coral.

Sea Country makes up about 70 per cent of the Anindilyakwa Indigenous Protected Area. Traditional Owners hold strong rights over land under the Aboriginal Land Rights Act, but over marine environments, the protections are thinner.

That is relevant in 2026. The manganese mine on Groote Eylandt has been operating since 1965 and faces water inundation problems as it heads towards a predicted closure in 2032, with a proposed ocean outfall that would pump gigalitres into the sea near local reefs. The community fishes here for food.

“Remote reefs like these have too often been treated as an afterthought in conservation.” — Associate Professor Emma Camp, UTS.

This research now feeds into a Sea Country Management Plan. Hopefully funding will now support classifying the types of coral, analysing if any are unique to the area, and testing how the corals handle heat and falling oxygen.

So there were seven papers in twenty years, with the eighth now coming to light. Suffice to say, there are a lot more reefs in the Gulf, and around this majestic coastline of ours, that nobody has looked at.

Surf’s up.

If you want to do your bit for our beautiful oceans this Science Week and beyond, the amazing people at ocean lovers festival have assembled this handy site.

Further Reading:

Benthic baselines of the Groote Archipelago’s key reefs in the wake of mass coral bleaching and Tropical Cyclone Megan, Wattle DPG, Pezner AK, Doheny A, England H, Anindilyakwa Land and Sea Rangers, Camp EF, PLOS One, 2026, https://doi.org/10.1371/journal.pone.0353017

Rangers and scientists map vulnerable reefs in the Groote Archipelago, University of Technology Sydney, 2026, https://www.uts.edu.au/news/2026/08/rangers-and-scientists-map-vulnerable-reefs-in-the-groote-archipelago

Submerged coral reefs in the Gulf of Carpentaria, Australia, Harris PT, Heap AD, Wassenberg T, Passlow V, Marine Geology, 2004, https://doi.org/10.1016/j.margeo.2004.03.002

Corals at the edge of environmental limits: A new conceptual framework to re-define marginal and extreme coral communities, Schoepf V, Baumann JH, Barshis DJ, Browne NK, Camp EF, Comeau S, et al., Science of the Total Environment, 2023, https://doi.org/10.1016/j.scitotenv.2023.163688