I just finished reading an article published in Estuarine Coastal and Shelf Science by Richard Feely from the Pacific Marine Environmental Laboratory here in Seattle and his co-authors from the University of Washington and the Washington Department of Ecology. These researchers sampled waters in Puget Sound on two cruises in February and August 2008, and concluded that pH and aragonite saturation levels in parts of Hood Canal are lower than what would be expected to be seen as solely as a result of increased carbon dioxide levels in the atmosphere.
I’ll get to the potential implications of this research in a bit, but first a bit of background, or what I think of as “Chapter 1″ of Ocean Acidification in the Pacific Northwest”:
Scientists are observing pH decreases in ocean waters globally as a result of increased carbon dioxide levels in the atmosphere. This is because carbon dioxide dissolved in sea water forms carbonic acid, and higher atmospheric concentrations of carbon dioxide will lead to higher carbonic acid concentrations in waters that are in equilibrium with the atmosphere. One of the main concerns of scientists is that the impact this lowered pH will have on organisms that build their shells or skeletons out of calcite or aragonite (a calcium carbonate mineral). If the pH of ocean waters becomes too acidic, these shells can dissolve—a condition researchers refer to as “corrosive”: seawater. In 2008, Richard Feely and other researchers published a paper in Science that reported the results of measurements made off of Washington that showed decreased pH in ocean waters, a local example of the global phenomenon being observed by scientists.
This study from 2008 had immediate legal implications. Using this research as primary support, the Center for Biological Diversity sued EPA, alleging that EPA violated the Clean Water Act by approving Washington’s list of impaired waters without inclusion of ocean waters as impaired by ocean acidification. EPA and CBD recently settled this litigation. I won’t go into excruciating detail regarding the allegations made by CBD, or the details of the litigation. If you are interested in those pieces of this story, Linda Larson and Meline MacCurdy wrote an excellent summary of the settlement between CBD and EPA that can be found on Marten Law’s website. Their article also contains a more in depth summary of ocean acidification than the one I’ve put together here, and a good discussion of the Clean Water Act.
Chapter 2 of Ocean Acidification in the Pacific Northwest:
This new article by Richard Feely could well be considered “Chapter 2” in ocean acidification science in the Pacific Northwest. In brief, what the researchers found is the same type of lower-pH ocean waters that were the subject of CBD’s lawsuit are entering Puget Sound. In Hood Canal, these waters remain fairly stratified—think in terms of a layer cake. This results in those waters retaining the low pH signature obtained in the open ocean. But, the real story is what happens to these waters once in Puget Sound. The researchers measured waters in Hood Canal that were even more acidic than the low-pH ocean waters observed in the 2008 open ocean study. Feely and his colleagues hypothesize that these waters are becoming more acidic once in Hood Canal due to the breakdown of organic material that is produced in the surface waters of Hood Canal. Essentially, algae blooms in Hood Canal result in the production of organic material in the surface waters. Those blooms die off, sink, and other organisms break that material down at depth. The result? Production of carbon dioxide in those waters, which creates carbonic acid and decreases the pH of those waters even further, including to the point where calcite and aragonite shells of organisms could begin to dissolve.
The paper discusses many possible implications of this cycle, including:
- Possible links to mass mortality of mussel populations
- Loss of oyster larvae in hatcheries
- Possible impacts on juvenile fish
So, here is why I think this might be “Chapter 2” of ocean acidification in the Pacific Northwest:
The first chapter was the 2008 ocean study and the CBD lawsuit. Chapter 1 is not complete because EPA has not finished its work under the settlement agreement with CBD. The local influence on the waters in Hood Canal can be considered Chapter 2, because those inputs may be partially caused by human activity, and could trigger a new type of regulatory or legal response. Production of organic material in Puget Sound and Hood Canal may be higher than it was prior to humans occupying this area due to nutrient inputs from urban runoff and other human sources. In essence, part of the local pH drop of these waters could be caused by a myriad of difficult to control sources of nutrients. I wouldn’t be surprised if this becomes another argument for the stricter control of nutrient inputs from non-point sources to Puget Sound. But, in forming a regulatory response to this issue, the difficulty will be deconvolving what is naturally occurring versus what is caused by humans. That being said, if you are faced with these two or three antagonistic effects (i.e., open ocean low pH waters being influenced by natural and human-caused local processes) leading to the bulleted results above, and want to do something about these impacts, decreasing the human-caused portions of algae blooms in Hood Canal may be a good place to start.
Interesting science that poses some complex and difficult policy implications. We’ll see how Chapter 2 plays out, and whether there is a Chapter 3.