Tag Archives: larvae

How Will Cod React to Global Warming? Researchers Subject Fish to High CO2 Levels to Find Out

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May 8th, 2014, By Eva Tallaksen, undercurrentnews.com

cod in high co2Scientists in Tromso, Norway, are exposing cod broodstock to high CO2 to find out how the fish will cope as the seas get warmer, and more acidic.

“The idea is to find out, how will ocean acidification affect aquaculture and wild fish?” said Christopher Bridges, zoology professor at the university of Dusseldorf.

It is hoped larvae scooped from five tanks at Nofima’s national cod breeding center will soon yield some clues.

Each tank contained 60 cod broodstock averaging 3-5 kilos in size, exposed to different levels of temperatures and acidity. The fish spawned March and April, and their larvae, which hatched in the past two weeks, are currently being tested.

“The key aspect will be to look at the larvae’s survival rate,” said Bridges.

If global warming continues as some scientists think, the oceans’ CO2 levels could reach 1,000 to 1,200 ppm (parts per million) by 2100, up from just under 400ppm today.

That would take the seas’ pH level down to 7.8, from 8.1 today.

Most the research into the seas’ growing acidity has focused on the impact on fish eggs or larvae, or on habitats. But few have so far focused on its impact on broodstock, said Bridges.

Bridges is one of the scientists involved in the project, which is led by the publicly-funded German Bioacid initiative. Cooperating in the project are Germany’s Geomar and Alfred Wegner Institute, working in Norway under the EU FP7 support project Aquaexcel using the facilities of Nofima.

In two of the tanks, the cod were kept at normal acidity levels (400ppm), but one tank had a temperature of 5 degrees Celcius, and the other 10 degrees. In two other tanks, the fish were exposed to CO2 levels of 1,200 ppm, again with one tank at 5 degrees and the other at 10 degrees.

These four tanks all used broodstock from farmed fish, bred by Nofima’s center. A fifth tank was filled with fish from the wild, but these were caught too late to be used for the experiment.

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Maine Confronts a Sea Change

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July 03, 2013 18:55
By Brad Warren
 
Bill Mook suspected trouble in the water when he first noticed plankton blooms dwindling, raising questions about the future supply of natural feed for the clams and oysters he raises in a tidal reach of Maine’s Damariscotta River.
 
Over the last decade he witnessed an increase in intense storms that brought torrential rains. Mook also spotted a pattern inside his hatchery, which spawns and produces oyster “seed” for his own and other farms in the region. After heavy rains, larvae and their tank-raised microalgae feed became harder to grow. Mook saw his tiny, new-hatched oysters circling at the bottom of the tanks instead of swimming actively through the water column as usual.
 
This was the same larval behavior reported by West Coast oyster hatchery managers when their larvae began dying in increasingly corrosive water, threatening “seed” supplies. The worst-hit animals failed to develop properly or even to “set”—a crucial step in which bivalves pick a spot to settle down and grow up.
 
The veteran producer began speaking out to other growers, fishermen and resources managers. He called for investigation of changes in seawater chemistry that may soon pack the kind of wallop that nearly wiped out seed supplies for West Coast shellfish farmers in the late 2000s.
 
The West Coast industry managed to temporarily avert that crisis by partnering with scientists to take careful measurements and devise adaptive maneuvers. But the episode generated lessons that are rippling through the world’s seafood industry. And the underlying threat is growing. Scientists have firmly linked the Pacific Coast oyster crisis to ocean acidification, a consequence of industrial society’s swelling emissions of carbon dioxide (CO2) from burning coal, oil and gas. 
 
If similar effects are showing up in Maine, can the state meet the challenge?.
 
On the West Coast, the effort to detect and dodge corrosive water did more than protect growers. It revealed a gathering danger to seafood supplies, jobs, and coastal communities. It also enabled Washington state—the nation’s largest farmed shellfish producer—to launch a comprehensive effort to understand this threat and begin defending its fisheries and coastal waters from souring seawater. I’m proud to play a part in this work.
 
Just over a year ago shellfish growers and tribal leaders persuaded Washington Gov. Christine Gregoire to create a Blue Ribbon Panel on Ocean Acidification, based on a proposal I drafted. Gov. Gregoire convened this bipartisan panel and tasked it to recommend strategies for the state to understand, adapt to, mitigate and remediate damage from acidification.
 
When the panel completed its report in November 2012, Gov. Gregoire promptly instructed state agencies to implement its recommendations. She reallocated $3.3 million in her budget to do the job, including funds for a new ocean acidification research center.
 
Washington’s initiative is the first of its kind, but it won’t be the last. Fishermen, growers, scientists, conservationists and coastal leaders are enlisting state governments to help understand the impacts of changing ocean chemistry and develop tactics to sustain seafood production and marine ecosystems.
 
Mook reckons it is time for Maine to devise its own strategy. “We need to get people who are stakeholders and experts and form some kind of group,” he says.
 
With its $330 million lobster industry, Maine has thousands of jobs at stake. Recent research has peeled back the impression that lobsters might be immune; preliminary findings in Maine and Nova Scotia show reduced growth and delayed development in high-CO2 water. Meanwhile Maine’s clam industry faces both an invasion of destructive green crabs and acidification that weakens shells, making the mollusks more vulnerable to predators.
 
As Maine considers its options, one lesoson from the West Coast can save a lot of trouble and money: “Turn on the lights.” That’s how Mark Wiegardt of Oregon’s Whiskey Creek Shellfish hatchery described the results when scientists from Oregon State University helped his team to measure and document effects of souring water on fresh-spawned larvae. “We wouldn’t be in business without it,” he says. One effective tactic: hatchery managers pump in seawater during sunny afternoons. By that time of day, the monitoring data show the water is “sweeter.” Whiskey Creek managers think that sun-loving seagrass near their intake soaks up enough CO2 to protect vulnerable larvae
 
To fix trouble, you need to see it. That’s why in Maine, my program is supporting research to help validate preliminary findings on acidification impacts on lobsters and clams. We hope these efforts can help Maine’s industry and policy leaders stave off future harm.