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Toxic oceans preserve ancient life

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Curtin University research showing that bacteria were responsible for the excellent preservation of a crab-like fossil during the Devonian period suggests that organic geochemistry could be a useful new tool for understanding ancient environments.  

The research, recently published in the prestigious journal Geology, showed that hydrogen sulphide dependant organisms (known as Chlorobi) and sulphate-reducing bacteria had preserved the shell and the muscles of the crustacean. Their presence proves there was a toxic ocean environment in the Devonian Period, potentially responsible for the mass extinction 380 million years ago.

PhD student Ines Melendez of the WA Organic and Isotope Geochemistry Centre (WA-OIGC) at Curtin led the study alongside her primary advisor, Professor Kliti Grice, Director of WA-OIGC. She says the research presents organic geochemistry as a new tool for palaeontologists, enabling them to identify invertebrate fossils and reconstruct their environments from a molecular point of view.  

“It’s like walking in on a crime scene, when all the evidence is still intact,” Ms Melendez said.

“Not only do we know the organism was a crustacean from the abundance of cholestane (formerly cholesterol) it contained, but we also know it was in a toxic ocean environment, from the biomarkers associated with the sulfate–reducing bacteria and Chlorobi. 

“By looking at the biomarkers and stable isotopes of fossils, we are able to reconstruct past environments, and can apply this technique to other ages of geological time.”

The fossil was collected from the Gogo Formation in the Kimberley Region of Western Australia on a field trip led by the Centre’s Senior Research Fellow, Associate Professor Kate Trinajstic.

Professor Grice said this research suggests the Devonian Period had similar paleoenvironmental conditions to the largest extinction event in the past 600 million years, where it was proved toxic concentrations of hydrogen-sulfide in ancient oceans, rather than a meteorite, were largely responsible for wiping out mass populations.

This research has been funded by the Australian Research Council under a 2nd QEII Discovery project grant awarded to Professor Grice. Professor Grice has also recently been awarded a Discovery Outstanding Research Award to continue this research with her team.

A copy of the paper is available at  


Ines Melendez, PhD student, Curtin University
Mobile:0416490043. Email:;

Megan Meates, Public Relations, Curtin University
Tel: 08 9266 4241, Mobile: 0401 103 755, Email:

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