New research led by Griffith University is the first to document multiple tropical oyster reefs across tropical Australia.
Oyster reefs are considered the "kidneys of the sea" and play a vital role in coastal health, but have declined by more than 99% in southern and south-eastern Australia and are considered to be functionally extinct.
Once thought to be the "temperate equivalent of coral reefs", oyster reefs are now being unearthed across tropical Australia – and they're bigger and more widespread than anyone, including lead researcher Dr Marina Richardson, expected.
"The footprint of some of these reefs are up to 5 hectares in size, making them the largest known intertidal oyster reefs in Australia," said Dr Richardson, a Research Fellow at Griffith's School of Environment and Science.
"And they're everywhere - from the southern limit of the tropics in the Gladstone region all the way around to the Gulf of Carpentaria. They're so extensive that they can even be seen from satellite imagery.
"Understanding the ecology of these overlooked ecosystems, and whether they need protection, is crucial to stop them from disappearing without us ever knowing they were there.
"It's been wonderful to explore their unique ecological functions, and through this we can now challenge previous assumptions about oyster reef ecology and advocate for their inclusion in conservation efforts."
This study is the first documentation of thriving tropical oyster reefs in northern Australia, which are so new to science that the oyster species responsible for building these reefs remained a mystery until now.
"Despite evidence of their decline, these reefs have managed to survive against the odds and their protection matters."
Dr Marina Richardson
Using modern molecular tools, the tropical reef-building oyster was finally identified as Saccostrea lineage B, a close relative of the Sydney rock oyster (Saccostrea glomerata) that is yet to be assigned a scientific name.
Lineage B also has a widespread distribution throughout the Indo-Pacific, where it is also likely to be reef-building, and was only reported for the first time in Queensland in 2024 during a Queensland Government and FRDC-funded oyster diversity project.
The detection of tropical oyster reefs hiding in plain site has now generated a completely new direction of research and collaborations between scientists, restoration practitioners, and citizen scientists working to map these ecosystems across tropical Australia.
Since the project started in June 2024, more than 60 new reefs have been identified so far across Queensland, the Northern Territory and Western Australia through a combination of satellite imagery and OzFish Unlimited's Great Shellfish Hunt.
"By understanding where these reefs are, how many are left and how they function, we can ensure that they're not left behind in the global restoration movement," Dr Richardson said.
The study 'Characterising tropical oyster reefs: invertebrate-environment associations and a newly documented reef building species' has been published in Marine Environmental Research.
