Acid test for ocean experts and shellfish sector

DOZENS of international experts will gather in New Zealand this weekend to tackle the problem of mounting acidification of the oceans.

The ocean acts as a sink for the excess carbon dioxide in the atmosphere from the burning of fossil fuels.

That’s changing the chemistry of sea water, which is becoming more acidic and posing a grave threat to a burgeoning shellfish industry.

Almost 50 chemists and oceanographers from across the Commonwealth will attend a workshop at the University of Otago over the coming week.

Increasing acidity means shellfish cannot build the shells they need to survive. The problem has already hit oyster farms in the US, Chile and Australia and in New Zealand, scientists are working with shellfish growers to ‘‘future proof’’ their industry.

Dr Christina McGraw, chair of the NZ Ocean Acidification Council, says the pH of oceans has dropped quickly, and significantly.

‘‘We can’t stop it until we reduce carbon emissions, but we can start thinking about ways to plan and mitigate for it,’’ she said.

Dr Cliff Law, of Niwa, said the ocean was 30 per cent more acidic than in the 19th century, and is predicted to rise to 150 per cent of pre-Industrial levels by 2100.

‘‘Ocean acidification has the potential to significantly impact marine ecosystems and economies, both around New Zealand and in the global ocean . . . there is much work to be done, and the collective power of the Commonwealth working together will be crucial.’’

Dr Jan Newton, a principal oceanographer from the University of Washington, has been studying high mortality rates on oyster farms in the US Pacific Northwest.

‘‘Shellfish growers here have noted effects from ocean acidification on their ability to raise oyster larvae,’’ she said.

‘‘Working together with ocean chemistry experts, they have undertaken active monitoring and developed ways of adapting their practices to help oyster production.

‘‘I think the lessons we have learned can apply to New Zealand aquaculture and I look forward to sharing our experiences.’’

Aquaculture is worth about $320 million to the economy and employs as many as 1000 people.

Sandford is working with a number of scientists at its Marlborough Sounds mussel farms and at a hatchery in Nelson. General manager aquaculture Ted Culley says selective breeding may ensure shellfish adapt.

‘‘If you think about selective breeding for sheep and cattle, you know we have been doing that for 1000 years – and we are still making improvements in their performance in their vitality and durability, so I think the future for aquaculture is still really exciting.’’

‘We can’t stop it until we reduce carbon emissions, but we can start thinking about ways to plan and mitigate for it.’ DR CHRISTINA MCGRAW, RIGHT