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A Sea Change
The first buoy is located in the Gulf of Alaska. The start to monitoring oceaning acidifcation in the country. This bouy is hooked up to a satellite to monitor it from the sky. Today, ocean acidification appears at the top of a growing list of environmental problems attributed to the rapid accumulation of human-emitted carbon dioxide in the atmosphere. As I figured global problem with catastrophic consequences for marine life forms.
The oyster larvae in Willapa Bay — a region that provides one-sixth of the nation’s oysters — failed to reach maturity for the fourth summer in a row.
Oyster hatchery managers called Feely, all of them asking a similar question: Could corrosive waters possibly be responsible for killing millions of oysters in Washington and Oregon?
Oysters in Willapa Bay have been there for over 100 years.
Suitable grounds for growing oysters are found in low intertidal and shallow subtidal areas. On more than 20,000 acres, the local industry is now concentrated on 10,000 acres and grows Pacific oysters.
Feely can’t say for sure whether acidic waters are to blame. “What we do know is that oyster farmers are finding more severe impacts when they see corrosive waters in their hatcheries,” Feely says.
While a number of environmental problems, including a low-oxygen dead zone of the coast of Oregon, could be contributing to the mass kill-offs of oyster larvae, Feely believes that corrosive waters are mainly responsible for exacerbating the bacterial infestation and killing off oyster larvae.
Hatcheries in the region report that their die-offs tend to occur after periods of persistent northwesterly winds, when deep waters well up and enter the bay, and the pipes that feed the hatcheries. The oyster larvae are swimming in these acidified waters, which can be corrosive enough to dissolve their fragile shells.
To make matters worse, the hatchery managers observe that Vibrio tubiashii seems to thrive in a more corrosive environment.Hatchery owners are seriously concerned about the future of the shellfish industry.
How will ocean ecosystems be affected by ocean acidification?
Feely: If they [marine plants and animals] cannot adapt, where will they go? Will they go to waters that have a higher pH and are more supersaturated? If so, what happens to the ecosystem that’s left behind? What happens to the fish that are dependent on these organisms for their food? This is a very serious question. And for coral reef systems in particular, for example, the skeleton of the coral reef system is the major home for 25 percent of all our fisheries that live in coral reef systems during some portion of their livelihoods. So it’s a critical component of the ocean ecosystem.
You can go back further in the geological record and look at ice core records to see what the impacts of CO2 have been and the changes in CO2 levels in the atmosphere. And what we find is that the atmospheric concentrations, over the last 800,000 years or so, have changed between about a 180 parts per million [of seawater] and 280 parts per million. But we are now as high as 385 parts per million at present. And by the end of this century we could be as high as 800 parts per million.
Clearly in the very far distant geological past, 35 to 50 million years ago, we’ve had CO2 levels that were much higher than they are at present. The difference is that the rate of change of CO2 is so dramatic now that it far exceeds any changes that have taken place in the past. We are changing the ecosystem so fast, we’re changing the ocean system so fast, that many of the organisms don’t have the ability to adapt to these changes that are taking place.
Around half of all carbon dioxide produced by humans since the Industrial Revolution has dissolved into the world’s oceans. This absorption slows down global warming, but it also lowers the ocean’s pH, making it more acidic. More acidic water can corrode minerals that many marine creatures rely on to build their protective shells and skeletons.
How severely marine life will be affected depends on whether and how much we reduce emissions of carbon dioxide from burning fossil fuels. The maps above show computer model simulations of present-day ocean pH (left) and two possible futures: one in which we quickly and significantly reduce carbon dioxide emissions (middle), and one in which we do not (right).
Current pH of Our Oceans
Since the Industrial Revolution, the pH of the ocean has already decreased from its historical global average of around 8.16 (slightly basic) to about 8.07 today. Because the pH scale is logarithmic, a difference of one pH unit represents a tenfold acidification.
The map in the middle shows projected ocean pH levels by 2100 for a possible future scenario in which humans commit to taking the necessary actions to limit temperature increase to 2°C during this century—a threshold considered by many industrialized countries to be the point at which we can avoid dangerous human influence on the climate. Under this scenario, the world’s energy portfolio places a balanced emphasis on all energy sources, both fossil fuels and renewable sources. By the end of this century, average ocean surface pH would fall to about 8.01—about 1.5 times more acidic than the waters were before industrialization.
The final map is built on the idea that humans will not take any steps to reduce emissions or carbon dioxide concentrations that would rise to around 1,000 parts per million (ppm) by 2100. That’s A three-fold increase compared to present-day levels. Until the economic downturn in late 2008, actual emissions since 2000 were on track to exceed this high-emission scenario.
In the high-emissions scenario, global average ocean pH levels would fall to around 7.67 by 2100, roughly five times the amount of acidification that has already occurred. Such large changes in ocean pH have probably not been experienced on the planet for the past 21 million years, and scientists are unsure whether and how quickly ocean life could adapt to such rapid acidification.
Those estimates are global averages, but local, seasonal, and regional changes cause pH variations throughout the global ocean. Around the equator in the Pacific Ocean, carbon-rich waters from the deep ocean rise to the surface during upwelling events, causing lower pH values in that region. More acidic waters are also present at high latitudes due to the fact that cold water holds more carbon dioxide than warm water.
These maps are based on analysis by British researchers collaborating through the AVOID Programme, using computer models of the global climate to project the likely response of ocean acidification to a range of emission scenarios. The models simulate ocean-atmosphere interactions, climate, ocean chemistry, and the complex feedbacks among them.
The computer simulations demonstrate that stronger and more immediate action can reduce the levels of acidification that would occur under a higher emissions scenario. Providing a range of future scenarios helps policy makers consider what impact the timing and aggressiveness of different strategies to reduce carbon dioxide emissions will have on future ocean acidification.
Despite the grim realities playing out in the ocean, Feely remains optimistic. “Now that we know about the problem, and understand its root causes, we can monitor the situation,” he says. “We can change the decisions we’re making. We can take steps to reduce our carbon dioxide emissions and take steps to protect the ocean.”
Still, critical questions remain. What areas of the ocean will experience the largest impacts? What species will be most affected? Will species adapt to changes in ocean chemistry, or will they migrate to different areas? Feely and Sabine and their colleagues won’t be able to answer those questions until they build and deploy the ocean acidification monitoring system they’ve designed. Our understanding of how the web of sea life will respond to ocean acidification is still in its early stages, but scientists believe ocean acidification poses a threat to the health of our ocean. Photo courtesy of NOAA.
“Ultimately, the most important question remains unanswered,” Feely muses. “Will humans decide to address this problem at its root by reducing carbon dioxide emissions?”
To learn more about Richard Feely’s and his team’s research on ocean acidification, please see the ClimateWatch article, titled An Upwelling Crisis: Ocean Acidification.
Bernie, D., J. Lowe, T. Tyrrell, and O. Legge (2010), Influence of mitigation policy on ocean acidification, Geophys. Res. Lett., 37, L15704, doi:10.1029/2010GL043181
Credit: Video copyright Oregon Sea Grant Communications, Oregon State University. Directed and produced by Joe Cone, videographer, and Stevon Roberts, video editor.
Feely, R.A. et al. (2008), Evidence for Upwelling of Corrosive “Acidified” Water onto the Continental Shelf, Science, v320, 1490-1492.
Feely, R.A. et al. (2004), Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans, Science, v305, 362-366.
Feely, R.A., Sabine, C.L., Fabry, V.J. “Carbon Dioxide and Our Ocean Legacy.” April 2006.
Frequently Asked Questions. Ocean Acidification Network.
International Scientists Find ‘Acidified’ Water on the Continental Shelf from Canada to Mexico. NOAA press release. May 22, 2008.
Ocean Acidification – From Ecological Impacts to Policy Opportunities in Current – The Journal of Marine Education.
Sabine, C.L., et al. (2004), The Oceanic Sink for Anthropogenic CO2, Science, v305, 367-371.
Seafood Choices Alliance. “Canaries in a coal mine: What shellfish can teach us about ocean acidification.” Contributed by Robin Downey of Pacific Coast Shellfish Growers Association. August 3, 2009.
Testimony of a Supervisory Chemical Oceanographer at NOAA’s Pacific Marine Environmental Laboratory, Richard Feely, before the House Committee on Science and Technology, Subcommittee on Energy and Environment (Chairman Nick Lampson, D TX-22) on HR 4174, the Federal Ocean Acidification Research and Monitoring Act of 2007 (FOARMA).
Welch, Craig. Oysters in deep trouble: Is Pacific Ocean’s chemistry killing sea life? Seattle Times. June 14, 2009.
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