Shellfish producers wary of growing ocean acidification as climate warms (text & audio)

Scientists are warning of the growing threat ocean acidification poses to marine ecosystems, industries and food security. A meeting of 350 scientists in Hobart, Tasmania this week at the Ocean in the High CO2 World conference is looking at ways to predict the rate of acidification and the regions most likely to be affected.

CSIRO Oceans and Atmosphere Flagship research scientist Dr Bronte Tilbrook said the ocean had experienced a decrease in pH of 0.1 since preindustrial times. “That doesn’t sound like much, but it’s a 30 per cent increase in the acidity level of the ocean because it’s on a logarithmic scale,” Dr Tilbrook said. “So they are pretty significant changes, but that’s the global picture [and] as you get into coastal regions, these changes can be amplified.”

Oceans have been effectively slowing the rate of global warming by absorbing carbon dioxide from the atmosphere. But the dissolved CO2 and the subsequent lower pH is having an impact on the entire marine food web, by disrupting the life cycle and the shell-making ability of many marine organisms.

Hard to tell how things will play out in the future

CSIRO senior research scientist Dr Andrew Lenton said while there had been a rapidly growing research investment in the area, the consequences were yet to be fully understood.

“For organisms that calcify, it will be much harder for those into the future to build their shells,” Dr Lenton said.

“It also means reproductive health, the life stages of the marine organisms may be impacted.

“What that means is that the whole tropic chain, the whole food web is impacted from the bottom to the top, and we have no idea how that will play out.”

Dr Richard Feely, from the US National Oceanic and Atmospheric Administration, said the near collapse of the $35 billion shellfish industry in the US in 2005 and 2006 was an early warning sign of what was possible.

He said the pH of seawater dropped from 8.1 to 7.6 on the west cost of the US, when local waters were mixed with a low pH upwelling that naturally occurred from April to November, ending with billions of oyster larvae deaths.

“We developed a technique to raise those waters to above 8.1 and they did just fine,” Dr Feely said.

“It allowed us to see, to look into the future. We were experiencing along our coast what we expect to see in the next 50 years.”

Network measures global ocean acidification

Scott Parkinson, from Australia’s largest shellfish hatchery supplying oyster spat, Shellfish Culture at Pipe Clay Lagoon in Tasmania, said ocean acidification was front of mind for his organisation.

The company is measuring sea water chemistry each minute with an electronic sensing probe, part of a CSIRO Global Ocean Acidification Observing Network measuring global acidification.

“We’ve certainly seen the data that comes from the US, that low pH, acidic water, is very detrimental to the bacterial community which is in association with the production of oysters,” he said.

“It changes the bacterial community. It allowed very detrimental bacteria to take over and cause massive mortalities throughout the operations in the United States.”

Sally Dakis, ABC News, 4 May 2016. Text & audio.

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