• Ocean acidification is seriously threatening oysters and other shellfish.
Scientists say changes in ocean chemistry as a result of climate change have the potential to wipe out mussels, oysters and other shellfish.
By
Kemal Atlay

3 May 2016 - 11:15 AM  UPDATED 3 May 2016 - 11:15 AM

It’s not just rising sea temperatures we should be worried about. A growing body of scientists is urging the world to turn its attention to the destructive phenomenon of ocean acidification. If you like shellfish, you might want to tune in now.

Hundreds of international scientists are gathering in Hobart this week for the 4th International Symposium on the Ocean in a High-CO2 World to discuss the impact of ocean acidification on the health of global marine ecosystems and associated seafood economy.

Ocean acidification occurs when increased levels of atmospheric carbon dioxide are absorbed by the world’s oceans. While it slightly softens the blow of global warming, it means there is more CO2 available to react with the seawater and reduce its pH levels, making it more acidic.

Amongst other effects, this has the potential to decimate shellfish species. The acidic environment makes it harder for organisms to grow and maintain their calcium carbonate shells.

“There are some places where we’re starting to see the effects of ocean acidification 50 to 100 years earlier than what we’d see in the rest of the world,” symposium co-convenor and senior researcher from the CSIRO’s Oceans and Atmosphere division Dr Andrew Lenton told SBS Science.

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Ecosystem could fall out of balance

 “We know that oysters and shellfish have harder times maintaining their skeletons as the pH of the water drops,” co-convenor Associate Professor Catriona Hurd from the University of Tasmania told SBS Science. “So it’s projected to be a problem for the oyster industry or shellfish industries in Australia.”

“If we start to lose them, then they’re going to be replaced by something else, and what they’ll probably be replaced by are organisms that don’t calcify – fleshy seaweeds, for example.”

Such is the threat to the industry that a number of studies are now focusing on selectively breeding oyster species to find ones that are more resistant to ocean acidification and better able to maintain their shells.

The shells are vital for the survival of the organisms – they control oysters’ ability to vertically navigate in the water and survive attacks from predators.

Dr Richard Feely, from the US National Oceanic and Atmospheric Administration, says that we can expect to see around 70% of shellfish species experiencing severe shell dissolution by as early as 2050.

This will be a result of both general ocean acidification and localised ocean acidification, where anthropogenic CO2 from the atmosphere combines with upwelling from the CO2 released from ocean plants and animals.

Shucked

According to Feely, extreme localised ocean acidification has the potential to wipe out entire industries in certain regions, such as along the US west coast.

“We had one year in 2007 where every single spawning group died out,” says Feely. “You spawn the oyster larvae and they have about two weeks to form a very early shell and they have to form that shell and develop that.”

“If they cannot form the shell they will simply die, and that’s what was happening in the tanks in the hatcheries themselves.

“They would have about 20 to 40 million oyster larvae swimming in the tank and when the pH was low enough they couldn’t produce their shell and die within two days.”

Alarm gripped oyster farmers in the US and they reached out to the government and scientific community for help – Feely says that a US$500,000 investment to install pH and CO2 sensors in the hatcheries has saved the industry around US$35 million.

“In the United States alone, the seafood industry is a US$35 billion a year industry and about half of that is shellfish, so for us it’s a major issue from an economic perspective,” says Feely.

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