Sydney rock oysters shrinking due to coastal acidification

Published on
August 21, 2018

Acidification of the marine environment is shrinking the size of Sydney rock oysters, a new report has found. 

The oysters, an iconic delicacy endemic to the waters of Australia and New Zealand, are getting smaller due to coastal acidification, according to a Natural Environment Research Council (NERC) study completed by Scottish and Australian scientists. NERC is the United Kingdom’s main agency for funding and managing research, training, and knowledge exchange in the environmental sciences. 

“The first thing consumers may notice is smaller oysters, mussels and other molluscs on their plates, but if ocean acidification and coastal acidification are exacerbated by future climate change and sea level rise, this could have a huge impact on commercial aquaculture around the world,” Susan Fitzer, a NERC Independent Research Fellow at the University of Stirling in Scotland, said in a press release after the results of the study she led were published in the journal Ecology and Environment. 

Coastal acidification occurs as freshwater runoff from acid sulfate soils decreases the environmental pH of coastal waters; rising sea levels and flooding can also play a role. Fitzer and her team found that the phenomenon was shrinking oysters and diminishing their populations at two commercial oyster farms in Wallis Lake and Post Stephens, both in the mid-north coast of New South Wales, Australia. 

Fitzer’s findings are from a larger, five-year NERC-funded project that is investigating biomineralization in commercially-farmed and wild shellfish to understand how climate change is impacting global aquaculture. Fitzer has previously linked rising acidification to weaker shells in mussels in Loch Fyne, Scotland, and she said she sees global ramifications for the study. 

“Acidic water is damaging oysters’ ability to grow their shells,” Fitzer said.

Ocean and coastal acidification is causing changes in how shellfish source carbon they use to grow their shells, Fitzer said. 

“We see lots of disorder in the calcite layers, because there isn’t enough carbonate in the water for the oysters to draw on for optimal shell formation and growth,” she said.

That could mean that seafood lovers around the globe could begin to find smaller and smaller oysters on their plates in coming years, Fitzer said.

Photo courtesy of Susan Fitzer/Natural Environment Research Council

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