Sound chemistry: ocean acidification’s effects on Puget Sound

Ocean acidification is Puget Sound’s silent killer for marine organisms – acidifying seawater cannot be readily seen, yet its effects are pervasive and detrimental to the Sound’s ecology and renowned shellfish industry. Ocean acidification occurs when the ocean absorbs carbon dioxide from the atmosphere, which creates a foundational change in seawater chemistry – carbon dioxide reacts with water to create carbonate and bicarbonate ions. As a result, seawater becomes more acidic.

You might be asking yourself, “Well, is ocean acidification really that big of a deal in Washington state?” The answer is yes! Washington is especially susceptible to ocean acidification due to three regional factors: (1) coastal upwelling, (2) runoff from land, and (3) less dissolved oxygen.

Upwelling occurs when offshore water rich in carbon dioxide with low pH is lifted from the deep ocean and brought to the surface with currents. As more carbon dioxide is emitted globally, more “carbon loading” is occurring in seawater causing upwelled water to be more acidic. This is particularly prevalent in deep bodies of water like Puget Sound. Consequently, upwelling of acidifying water will continue to increase as humans participate in activities that produce carbon dioxide emissions. In addition, runoff of excess nutrients from agriculture or animal waste; and local emissions of carbon dioxide, nitrogen oxides, and sulfur oxides absorbed by seawater from the atmosphere are contributing to ocean acidification. However, local concentrations due to these factors will vary by location. Lastly, low levels of dissolved oxygen, otherwise known as hypoxia, lower pH as well. For example, this occurs in Hood Canal during the warm summer months when there is less wind. The waters at the surface and the bottom of the Canal tend to mix less in these conditions. Less mixing leads to stratification where the freshwater from surrounding tributaries sits near the surface, on top of the canal’s denser salt water. As a result, oxygen-rich water does not reach the lower depths and can be harmful for less mobile marine organisms.

Now, you may wonder how this impacts the marine life in Puget Sound. Unfortunately, more acidic seawater creates significant challenges in the early stages of life for calcifiers that need calcium to form shells and other body parts. Ocean acidification can also lead to slower growth rates and increased mortality rates for these vulnerable species. This may seem like a small issue with calcifiers only making up 30 percent of Puget Sound’s marine species, but these marine organisms are responsible for making Washington state the nation’s leader in shellfish production and export. Calcifiers include oysters, clams, scallops, mussels, abalone, crabs, geoducks, barnacles, sea urchins, sand dollars, sea stars, and sea cucumbers.

Ocean acidification is not only challenging for marine organisms, but for shellfish growers who rely on Puget Sound as a source of income. To address this pressing environmental issue and its looming  economic impact, the Washington Shellfish Initiative was updated in 2016 by Governor Jay Inslee to incorporate ocean acidification strategies developed by the Marine Resource Advisory Council and the Washington Ocean Acidification Center. In addition, the School of Marine and Environmental Affair’s Assistant Professor, Ryan Kelly, is leading two research projects on Puget Sound’s ocean acidification issue: (1) analyzing changes in community composition across pH gradients in Hood Canal and the San Juan Islands; and (2) assessing mitigation efforts of eelgrass beds to pH stress. If institutions and their collaborators continue to move forward in researching and monitoring the effects of ocean acidification in Puget Sound, coupled with the industry incorporating adaptive management practices, this staple Washington economy might have a fighting chance.

Even though tackling ocean acidification feels like a huge task, fear not! The Washington Sea Grant suggests six ways YOU can take action to help limit ocean acidification in Puget Sound:

  1. Keep poop out of Puget Sound – Picking up your pet’s waste and maintaining your septic system will ensure the excess nutrients from human and animal waste do not make it into Puget Sound.
  2. Rideshare – Taking advantage of carshare programs like Car2Go, ZipCar, and ReachNow reduces the need for owning a car; or opt for carpooling with a co-worker or friend to minimize your carbon footprint.
  3. Eat cautiously – Choosing to eat locally will significantly reduce the carbon dioxide emitted for transporting your food; or participate in “meatless Monday”. Meat is more carbon- and water-intensive to produce, so try eating veggies and grains instead.
  4. Act collectively – Engaging with your community to reduce carbon dioxide emissions will have a larger impact than if you act alone – amplify your impact through community action.
  5. Directly help Puget Sound – Volunteering for habitat restoration or invasive species monitoring is good for the Sound and will help it withstand ocean acidification.
  6. Voice your opinions – Reaching out to your elected officials to influence policy and industry leaders can be easy and effective. If you are passionate about reducing the impacts of ocean acidification in Puget Sound, let your elected officials know.

“Ocean acidification presents a significant challenge to Washington’s marine environment and economy but it is a challenge that can – and must – be met.” – Washington State Blue Ribbon Panel on Ocean Acidification

Ashley Bagley, University of Washington, 5 February 2018. Blog.


1 Response to “Sound chemistry: ocean acidification’s effects on Puget Sound”

  1. 1 Lina Hansson 9 February 2018 at 12:01

    Note that the terminology used in this article is misleading. The definition of “acidic” in the Oxford English dictionary is “having the properties of an acid; having a pH of less than 7″. Despite the process of ocean acidification, the oceans are alkaline (pH higher than 7) and will not become acidic in the foreseeable future. Hence, “acid” or “acidic” should not be used when referring to seawater. Note that there are few exceptions, seawater can be acidic in the immediate vicinity of CO2 vents or in purposeful perturbation experiments.

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