Thomas Wernberg is a Professor of Marine Botany in the University of Western Australia’s Oceans Institute. He aims to transform our understanding of Australia’s Great Southern Reef.

Australians know their Great Barrier Reef, but fewer are aware of the Great Southern Reef. Yet 70 percent of our population lives within 50km of this vast, magnificent ecosystem.

I grew up on a small island in the Baltic Sea in Denmark, and always had a close relationship with nature. I was always outside, playing at the beach, snorkelling every summer. When I moved to Australia 25 years ago to start my PhD, I spent a lot of time working on the kelp forests here. Over the years, as I started to connect with students and the many amazing researchers from different parts of southern Australia, we got to talking about how remarkably unique the southern coast reef system is as a whole and how there was no appreciation of this.

It’s easy to understand why the Great Barrier Reef has been so successful in getting attention. It has a brand – an identity. Clear water and bright coral. Yet the Great Barrier Reef is actually a collection of maybe 3000 or so individual reefs dominated by corals. There’s great variety, however, and among the coral in some parts you’ve got mangroves, in other areas seagrass or seaweed. Yet we all know this greater ecosystem as the Great Barrier Reef, because everyone understands that the colourful corals are the defining feature.

We realised how important it is that an ecosystem like the “Great Southern Reef” (GSR) has an identity for people to relate to, to understand it, and eventually to care for and protect it. It was actually one of my PhD students, Scott Bennett, now a marine researcher at University of Tasmania, and I who coined the term around ten years ago. Scott came up with the name and we wrote an initial paper on it, inviting a bunch of other marine scientists from across the south coast to contribute, and it got traction from there. I wouldn’t claim that we were the first to think about the system as one unit, but the name struck a chord: we gave it an identity, so we could then market it, and communicate its importance.

I think the world was ready for a bit of seaweed love. Just as corals unite the features of the Great Barrier Reef, seaweed connects the Great Southern Reef. There is one particular kelp species that we initially identified as the defining feature – the golden kelp (Ecklonia radiata). It’s found from the coast of WA all the way around the south coast and Tasmania to the waters of southern Queensland.

Golden kelp and large seaweeds are still the defining feature of the Great Southern Reef, but we now talk more broadly about this vast coastline as an interconnected marine reef ecosystem, because there are so many more components than just the kelp forests.

It is important we care about this unique reef system – treasure it. It’s a lot more than rocks with slimy seaweeds washing up on your local beach. The thousands of species are actually all components of a massive ecosystem that extends for thousands of kilometres, all of which is highly interconnected by ocean currents. We can see this from the many common species spread across large parts of the Great Southern Reef. There are also lots of differences between individual regions but as a whole the GSR is a biodiversity hotspot for cold-water species where up to 70% of seaweeds, invertebrates and reef fishes are found nowhere else on the planet.

My own research has been mostly about climate-driven impacts and marine heatwaves. We’ve seen increases in temperatures along both the east and west coasts of Australia driving great contractions of seaweeds, including golden kelp. During the extreme marine heatwave in 2011 in WA, we lost golden kelp from around 100km of coastline, and it thinned out for another several hundred kilometres. It hasn’t recovered yet – and this is almost 15 years ago.

It was predominantly due to water temperature, but a lot of things happened: the heatwave was associated with a strong flow of the Leeuwin Current from the north to the south, so many fish herbivores that are normally found in coral reef habitats suddenly appeared in the kelp forest. So there was also increased grazing pressure.

My laureate fellowship will try to draw together all of the data I have collected over the past 25 years and all that we have learned, and then add new information where it’s required.

There are a lot of basic ecological questions that need answering. How nutrient dependent are the different seaweed species? How do they respond to temperature increases? A lot of species are still undescribed. Every year, new species are discovered.

We also want to understand under what circumstances the Great Southern Reef species are vulnerable, and under what circumstance they’re resilient. Science is understandably concerned with why things die in certain circumstances, but we have spent less effort trying to understand where and why they may survive and even thrive. By understanding the traits of the ecosystem contingent with survival, we can find a key to understanding what we need to do to promote resilience.

We also don’t fully understand the value Australia gets from having one of the planet’s most unique, temperate marine ecosystems at our doorstep. Not all of the values can be economically valued – the reef’s cultural importance cannot be overstated but is very hard to quantify. Learning more about the Great Southern Reef and all the many values it provides – in the broadest possible meaning of the word, is important to strengthening its value proposition.

As told to Graem Sims

Also in this series 2024 ARC Laureate Fellows:

Energy transition and communities: Professor Chris Gibson

Plate tectonics: Professor Alan Collins

Predicting groundwater discharge Professor Andrew Baker

Unravelling the mysteries of the immune system Professor Gabrielle Belz

Researchers hope to monitor Antarctic vegetation remotely Professor Sharon Robinson

How to build a quantum computer Professor Andrea Morello

Feature: the great southern reef