Aquaculture for all

Study on Impact of Ocean Acid Levels on Shellfish

Crustaceans Water quality Sustainability +7 more

CALIFORNIA, US - Bodega Bay scientists are investigating the danger from increasing levels of acid in the ocean, which could devastate the state's shellfish industry.

It is painstaking work that requires the team to wade through knee-deep mud at Tomales Bay to collect native Olympic oysters and then raise their young in salt-water tanks under conditions that mimic climate change, reports Press Democrat.

"Very little is known about how ocean acidification is unfolding, other than it is," said Susan Williams, director of the Bodega Marine Laboratory, which is part of UC Davis. "We are already seeing dramatic effects."

The evidence is seen in the dissolving shells of some mollusks and disappearing mussel beds. And researchers, with the backing of more than $4 million in University of California and federal funds, are trying to identify the long-term consequences of the ocean's changing chemistry.

So far, the research has been limited to Olympia oysters, a native species that grows in the wild. But the conditions apply to other shellfish, such as abalone, clams, mussels and sea urchins.

Oysters are 'the canary in the coal mine', according to marine lab biologist, Brian Gaylord.

The amount of carbon dioxide in the atmosphere has increased 30 per cent in the past 150 years and, with climate change, is predicted to double in the next 100 years.

"What happens in the ocean mirrors what happens in the atmosphere," said Tessa Hill, an oceanographer and chemist at the lab.

The ocean absorbs the carbon dioxide and that changes the chemistry of the water to make it more acidic, which inhibits the ability of shellfish to form shells, Dr Hill told Press Democrat.

The research involves collecting oysters in Tomales Bay, letting them spawn and then putting the larvae into conditions that introduce differing levels of carbon dioxide into the water. The juvenile oysters are then measured and studied.

The researchers also will launch buoys in the ocean off the Bodega Bay lab and in Tomales Bay to measure acid levels, temperatures and salinity.

So far what they have seen is a 40 per cent reduction in shell size and a slower rate of respiration for juvenile oysters that are raised under conditions simulating the atmosphere of 2100, Dr Gaylord said.

They still do not know whether shells are going to be weaker and thinner, making shellfish more vulnerable to predators, and whether the changes in ocean acidity will shorten their life spans or cause fewer to live past the larval stage.

"We don't know yet if the baby oysters have less chance of surviving. There may be more dying. This is what we will be looking at in the future," said Eric Sanford, a lab biologist.

The research began 18 months ago, and has been boosted by a a three-year, $600,000 grant from the National Science Foundation. The UC system has also given the lab, the Scripps Institution of Oceanography and UC Santa Barbara each $1.1 million for the research.

The Bodega Bay lab has received an additional $235,000 from the National Science Foundation to convert four rooms to sealed chambers in which the atmosphere can be controlled to imitate climate change.

Shellfish farms in California had $16.4 million in sales in the past fiscal year, according to the Pacific Shellfish Growers Association in Port Townsend, Washington.

Tod Friend, owner of the Tomales Bay Oyster Co., said the effects could be far-reaching.

"The ocean is the lungs of the planet and it is taking in all this carbon; the ocean is going to go acid and shell-making critters are not going to be able to do it," Mr Friend said.

"That is highly speculative but I worry about it, in the long run. I am trying to leave this business to my kids, but in time it could be the death knell of our industry," he added.

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