The GSR, vast as it might be, is the classic hidden treasure. Bringing in more than Aus $7 billion annually in fishing and tourism dollars alone, and within a short drive of some 70% of Australians, one might think its fame would rival that of the Great Barrier Reef.
Yet for most, it remains largely out of sight, out of mind. Until a multi-disciplinary team of scientists, including Craig Johnson, published a paper in 2016 arguing for its recognition, the GSR didn’t even have a name.
A spotted handfish clambers along the bottom in the Derwant River estuary
near Hobart. Above: unusually, southern swimming anemones like this one off Maria Island are mobile. They can release their grip and swim, albeit clumsily, to a new patch of kelp in the forest.
The reef’s relative obscurity and under-appreciation are likely due, at least in part, to the understated qualities of the organisms that define it: kelp and other seaweeds.
This is the stuff that fouls propellers and public beaches, that twines around your limbs should you be hardy enough to swim in the frigid waters where it resides.
Unlike their psychedelically hued coral neighbours to the north, most seaweeds – there are thousands of species – are green, and brown, and occasionally a bold, rusty red.
Many of their cohabitants are dressed to match. Still, despite this modest appearance, discounting and undervaluing seaweeds and the complex and important eco-systems they support, would be – has been – a grave mistake.
Kelp and other seaweeds aren’t plants. They’re macro-algae, lumped into the same hodge-podge taxonomic group that encompasses amoebas and slime moulds, but the comparisons are inevitable.
Like plants, they photo-synthesise.
They have leaf-like structures, called blades, that capture sunlight and convert it into storable carbohydrates.
Root-like structures called holdfasts anchor them to the bottom. Stem-like structures, called stipes, carry their blades toward the sun – growing, in the case of giant kelp, at an astonishing rate of 27cm a day.
And like simple plants such as ferns, seaweeds reproduce by releasing spores into their surroundings.
While the physiological resemblance is notable, the functional similarities between seaweeds and plants are far more important.
Like the trees in a rainforest, seaweeds are the foundation of their world, says Adriana Vergés, a marine ecologist at the University of New South Wales.
“They support entire ecological communities,” she explains. “This includes hundreds of species that get shelter, food, and habitat from these seaweeds.”
A male weedy seadragon photographed off the Tasman Peninsula carries eggs on the underside of its abdomen.
Among the GSR’s many inhabitants are otherworldly animals such as giant cuttlefish and weedy seadragons that draw scuba divers from around the world.
Endangered species such as grey nurse sharks and spotted handfish also call the reef’s underwater forests home.
Not least are economically important species, including rock lobsters and abalone – the invertebrates that support Australia’s two most important fisheries, collectively worth some $357 million annually. To scientists like Vergés and Johnson, who have spent decades studying seaweeds and their decline, the value of these eco-systems is undeniable.
Some of that value is economic, but much of the GSR’s inherent worth lies in the astounding diversity of species it supports.
And much of that diversity is unique. According to the 2016 paper that argued for the reef’s recognition and protection, 30-60% of its species are found nowhere else on Earth.
Geographic isolation – the same factor that gave rise to marsupial mammals – is partly responsible for the GSR’s abundance of unique organisms, the authors wrote.
But so, too, have been the region’s geological and climatic conditions – environmental factors that remained remarkably stable here for 50 million years before the Industrial Revolution.