Monash University scientists unlock seaweed secrets that could transform climate models
New research challenges a fundamental assumption in marine science.
A team of researchers from Monash University has made a paradigm-shifting discovery that could reshape our understanding of greenhouse gas emissions from the ocean.
Published in Nature Geoscience, the study reveals that oxygenated sandy coastal sediments, once considered inhospitable to methane-producing microbes, are in fact a major and previously overlooked source of methane.
Led by Professor Perran Cook and PhD candidate Ning Hall from Monash University’s School of Chemistry, and the Water Studies Centre, the research identifies a new class of aerotolerant methanogens that thrive in dynamic coastal environments.
These microbes produce methane by metabolising compounds released from decaying seaweed and seagrass, even in the presence of oxygen.
“This challenges a fundamental assumption in marine science,” said Professor Cook.
“Methanogenesis was thought to occur only in oxygen-free environments. We’ve now shown that these microbes survive oxygen exposure with no ill effects.”
The team conducted fieldwork across Port Phillip Bay and Westernport Bay in Victoria, as well as sites in Denmark.
Using a combination of in situ monitoring, laboratory experiments, and genomic analysis, they isolated two new strains of methanogens capable of rapid recovery and methane production following oxygen exposure.
“Our findings suggest that permeable sandy coasts, which make up half of the world’s continental margins, may contribute far more to global methane emissions than previously thought,” Professor Cook said.
“This has major implications for climate modelling and carbon accounting.”
The study also reveals a feedback loop between coastal vegetation and greenhouse gas emissions.
As seaweed and seagrass decay, they release methylated compounds that fuel methane production, potentially offsetting the carbon sequestration benefits of these ecosystems.
“With rising sea temperatures and increasing nutrient pollution, we’re seeing more frequent algal blooms and biomass accumulation on beaches,” said Professor Cook.
“This could lead to larger and more frequent pulses of methane to the atmosphere.”
The research complicates the narrative around “blue carbon” strategies, which promote coastal vegetation as a climate solution.
“Our work and that of others suggests that methane emissions from decaying biomass may offset much of the CO₂ removal attributed to these ecosystems,” Professor Cook said.
The study is supported by the Australian Research Council (ARC) and conducted in collaboration with partners from the University of Southern Denmark, the Securing Antarctica’s Environmental Future (SAEF) Research Program, and the Monash Biomedicine Discovery Institute.
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