Ocean Acidification: The Local Story

Corrosive seas aren't just happening "somewhere out there."
This post is part of the research project: Northwest Ocean Acidification
Mussels at Pike Place Market

opacity, flickr

When people learn that carbon dioxide pollution is turning our oceans more corrosive, it’s tempting to decide that the problem is too big for any person or local government to tackle.  But as our knowledge of ocean acidification continues to evolve, it turns out that in hotspots like Washington State, local factors—from nutrient pollution to seasonal currents and maybe emissions from ships or our own traffic—are playing a role too.

As Betsy Peabody, executive director of Puget Sound Restoration Fund, put it at this week’s meeting of the state’s Ocean Acidification Blue Ribbon Panel:

This is not just the carbon story that we’ve been hearing about happening somewhere out there. It’s different. It’s here.

The bad news? These local drivers are combining with rising global carbon dioxide emissions to make local waters increasingly acidic and put the Northwest on the leading edge of destructive changes in ocean chemistry.  For example, seawater in the depths of Hood Canal is already among the most corrosive found anywhere on earth. As that trend accelerates, it could profoundly change our marine systems, what appears on our dinner plates and whether shellfish farmers and, potentially, commercial fishermen will be able to stay in business.

The good news? While Washington State can’t do much about global carbon emissions, it does have some control over the local impacts that are contributing to the problem. Figuring out what those contributors are, and where the opportunities are to better control them, is one of the tasks of the blue ribbon panel that Gov. Christine Gregoire convened to look at the problem of ocean acidification. Washington State is the first to tackle the issue, and other states whose economies depend on a healthy seafood industry (such as Maine) are looking to us for solutions.

The basic problem is that excess carbon dioxide causes seawater to become more acidic (although it still remains above neutral on the pH scale). These chemical changes also bind up carbonate ions, which thousands of species of marine creatures need to build shells and skeletons. As those ions become scarce, those creatures have a hard time building and maintaining those protective structures. Although responses to acidifying seas vary widely among different species, mollusks such as oysters and clams and tiny creatures at the bottom of the food chain appear particularly vulnerable so far.

Since the ocean absorbs roughly a third of the carbon dioxide emissions we release into the atmosphere, rising climate pollution is making the oceans more acidic worldwide. This long-term trend is what scientists refer to as “ocean acidification.” But there are other sources of carbon dioxide in our local waters, which are contributing factors to the problems that have already begun to affect the state’s $270 million shellfish industry.

Here are some of the local influences that the panel is investigating:

Nutrient Pollution

Excess nutrients that come off our streets, lawns, and farms can fuel tremendous plant growth and algae blooms at certain times of the year. As these plants sink to the bottom and decay, they give off carbon dioxide that can cause localized waters around the Sound to become even more corrosive. So where do these nutrients come from? There are many potential sources: septic systems, wastewater treatment plants, dairies, irrigated agriculture, residential fertilizers, stormwater, and erosion to name a few.

In Hood Canal, researchers have done extensive work to try to figure out the sources of these nutrients and found that leaky septic systems are among the largest source in summertime when algae blooms are most problematic. Other studies have quantified the contributions of dissolved inorganic nitrogen into the Sound from wastewater treatment plants and rivers, but we don’t know as much about what sources may be exacerbating the acidification problem in other specific locations around the Sound.

Seasonal Upwelling

In Washington State, and along the Pacific Coast in general, seasonal winds in spring and summertime draw deeper and colder water up from the bottom and towards the surface and shorelines. It’s a natural process that happens to create hotspots of corrosive water because deeper water is also richer in carbon dioxide. This “upwelled” water will become more corrosive in the future as atmospheric carbon dioxide levels continue to rise.


Rivers, especially large ones such as the Columbia or Fraser rivers, significantly affect ocean chemistry near their mouths. Freshwater is more acidic than seawater, and rivers can also wash nutrients and other forms of pollution into the ocean.

Maritime Pollution

Researchers are interested to know whether diesel emissions from ships, which give off nitrogen oxides and sulfur oxides, are having a disproportionate impact on acidity in local waters. These are the same components found in acid rain, and more research is needed to determine how much of an influence those pollutants may be having.

Automobile Pollution

The city of Seattle itself generates a lot of carbon dioxide emissions, particularly during peak commute times. Researchers would like to investigate whether all those tailpipes spewing carbon dioxide on I-5 are having any direct impact on local waters.

Part of Washington’s ocean acidification panel’s charge is to lay out what further research and monitoring is needed. But members also hope to take what we know so far and recommend actions local governments can take right now to begin working on the problem. There are a lot of potential levers, from pollution regulations to incentives that get people to drive less to voluntary programs that help landowners control runoff. Ryan Kelly, a science, law and policy analyst with Stanford’s Center for Ocean Solutions who compiled this report on California laws and programs that might be brought to bear on ocean acidification, is working on a similar one for Washington State.

But in order to know how to prioritize those actions, policymakers need to understand which local drivers are the most significant contributors to Washington State’s acidification problems. Because we’ve only recently even recognized the threat, there’s still a fair amount of uncertainty there. The most obvious one to tackle would seem to be nutrient pollution, but as panelists acknowledged at this week’s meeting, it is hardly a new one. As Kelly put it:

There are no big solutions. There is no silver bullet to this problem. It’s more likely that a smaller constellation of measures will make a dent here…But this is hardly low hanging fruit. Non-point source pollution has been a problem for a long time, and it’s a big political battle. The question is what can the Blue Ribbon Panel do within its jurisdiction about it?

The panel has several more meetings this summer, and expects to wrap up its work early in the fall. Stay tuned to see what answers they come up with.

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  1. Mark Farmer says:

    Thank you for this article. Indeed ocean acidification is the most worrying aspect of global CO2 increases. You in Washington are seeing the first effects but within 75 all coral reefs in the tropics will collapse if we do not get off an ancient carbon-based economy within the next 10-15 years.

    This problem keeps me awake at night.

  2. Gregory Sotir says:

    Thanks for the article on this important subject. This just shows that the states need to take control of industrial production of CO2 as quickly as possible to protect their own resources. Washington state should push for a full EIS for coal transport through thee region. The combustion of this coal will contribute a whole lot of CO2, and increased diesel contamination of the Columbia Gorge ill also accentuate the problem.

    If the Feds are not willing or able to force industrial conglomerates to bring CO2 levels down (now at 400ppm in the Arctic), then the states must act to protect their resources and citizens health.

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