Sydney rock oysters adapt to climate change

Rock oysters in Sydney Harbour. Photo Stefanie Zingsheim.

Rock oysters in Sydney Harbour. Photo Stefanie Zingsheim.

Professor Maria Byrne at University of Sydney and Dr Susan Fitzer at University of Stirling in Scotland have discovered Sydney rock oysters can adapt their shells.

Sydney rock oysters selectively bred for fast growth and disease resistance are able to create their own defences and protect themselves from ocean acidification, according to new research published today in Global Change Biology . They do this by adjusting the way that they make their shells.

This is good news for oyster farmers in NSW. The $35 million industry , which includes the Sydney rock oyster, Pacific oyster and the native, flat oyster, has been threatened with poor harvests due to acidification of oceans. But now University of Sydney scientists working with international colleagues have shown that selectively bred Sydney rock oysters can defend themselves from this threat, coping better than the wild variety of the delicacy.

The Sydney rock oyster, Saccostrea glomerata, forms the basis of a large aquaculture industry in coastal and estuarine locations in south eastern Australia.

"This is a good news story in terms of climate change," Professor Maria Byrne from the Sydney Environment Institute at the University of Sydney said. "We have found these oysters that have been bred for fast growth or disease resistance also have a preadaptive resilience to the rising levels of acidification in our oceans. This is good news for the Sydney oyster farmers because they already use these oyster families in their aquaculture leases, however we still don’t know if the wild type of Sydney rock oysters will be able to adapt quickly enough to also be resilient to acidification."

Oceans and climate change

Ocean and coastal acidification - the ongoing increase in the acidity of the world’s oceans - hampers some organisms, such as oysters, from producing and maintaining their shells. However, experts now believe that for these oysters there is a potential solution to the problem.

A team at the University of Sydney and the University of Stirling (Scotland) studied Sydney rock oysters being farmed in New South Wales at Wallace Lake and Port Stephens and found that resilient families of the oyster generated through targeted breeding can cope better with more acidic seawater conditions than wild oysters.

Professor Byrne said: "The Sydney rock oyster industry is in particularly good shape because through decades of breeding the NSW Department of Primary Industries has generated oyster families that are by coincidence resistant to acidification. These oysters are better able to grow in naturally acidified coastal environments than wild type oysters and they do this by adjusting the way that they make their shells." 

Oyster Aquaculture

This work addresses a major problem in oyster aquaculture. Coastal acidification in Australia and in many other regions around the globe is damaging oysters’ ability to grow properly - with such changes in shell growth mechanisms likely to have implications in the future. For example, we may see the production of smaller oysters with thinner shells - leaving them prone to fracture and at risk of shell damage during culture and harvesting.

Dr Susan Fitzer from the Institute of Aquaculture at the University of Stirling said: "Our research shows, for the first time, that oysters selectively bred for fast growth and disease resistance can alter their mechanisms of shell biomineralisation, promoting resilience to acidification."

Commercial aquaculture is vulnerable to the impacts of ocean acidification - caused by increasing carbon dioxide absorption by the ocean - and coastal acidification, driven by land runoff and rising sea levels.

International Oyster Research

Working with the NSW Department of Primary Industries, the University of Sydney and the Scottish Universities Environment Research Centre, the team characterised the crystallography and carbon uptake in the shells of the Sydney Rock Oyster (Saccostrea glomerata) farmed in habitats affected by acidification from land runoff. The scientists looked at oysters from families selectively bred for fast growth or disease resistance to assess whether these factors were associated with changes in the mechanisms of shell biomineralisation, in comparison to wild oysters.

Dr Fitzer said: "Importantly, our research was able to show that selective breeding in oysters is likely to be an important global mitigation strategy for sustainable shellfish aquaculture to withstand future climate-driven change to habitat acidification."

The paper is published in the journal Global Change Biology. It follows a previous paper in August 2018 and a Conversation article by Dr Fitzer in January 2019.

Declaration: The Natural Environment Research Council supported Dr Fitzer’s work through an Independent Research Fellowship, while Professor Maria Byrne (University of Sydney) participated in the study with the backing of the Australian Research Council.

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