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2015 Puget Sound Factbook Book | v3.0 could increase as population growth and urbanization continue, and if drought-induced cutbacks in Californian agriculture lead to more demand for farmland here, especially for dairy farms. Another factor has also made the Northwest a frontline for acidification: the importance of its shellfish industry, together with the special vulnerability of one key component, larval oysters. University of Washington researchers recently identified worrisome effects on other species with vital commercial or ecological importance. Acidification affects the ability of mussels to produce byssus, the tough adhesive threads that anchor them to their rocks against waves and surf–a life-and-death matter for a mussel. The native bay mussel (Mytilus trossulus) also loses byssal strength when water temperatures surpass 20 o C, whereas Mediterranean mussels (M. galloprovincialis) grow more byssus as the waters warm (O’Donnell et al., 2013; Carrington & Friedman, 2015). This suggests a potential species succession, from native to introduced mussels, as Puget Sound becomes warmer and more acidic. Potentially more ecologically devastating are acidification’s effects on copepods and krill, small swimming crustaceans at the base of the marine food web. The copepod Calanus pacificus, common in Puget Sound, shows reduced hatching success at the pH levels expected by 2100, though impacts vary between broods and some continue to breed successfully. Overall, the copepods fare better than the likewise common krill Euphausia pacifica, which suffers both reduced growth and higher mortality at low pH (Keister & McElhany, 2015). Krill also inhabit deeper, more acidic waters than copepods, compounding their exposure. Their loss would be grievous for the fishes, seabirds, and whales that depend on them. Sea level rise Although Puget Sound’s shoreline terrain is very different from flatbottom Florida’s, it still includes dozens of deltas, estuaries, and shallow bays that are acutely exposed to rising seas, as well as the economically vital fill-dirt harbors of Seattle and Tacoma. Sea-level projections vary more than many others thanks to the many variables influencing them; the seas along Washington are expected to rise somewhere between 4 and 56 inches by 2100. At a midpoint outcome of 27 inches’ rise, 91 percent of the estuarine beach and 77 percent of the brackish marsh along Port Susan, Padilla, and Skagit Bays will be inundated, with similar if less dramatic effects all the way down to Budd Inlet and the Skokomish delta (Glick et al., 2007). These inundations will certainly disrupt habitats, but they may in the end create valuable new ones. Many beaches, wetlands, and dry areas will become tidelands, saltwater marshes, and, possibly, eelgrass beds—valuable carbon sinks and nurseries for marine life. Urban inundation offers no such tradeoffs; protecting and relocating utilities, transportation, and other low-lying and underground infrastructure will be a multibillion-dollar challenge. Higher ground? In 2012, the National Research Council reported that north of Cape Mendocino, California, the Pacific Coast is rising 1.5 to 3.0 millimeters per year, thanks to uplift as the offshore Juan de Fuca Plate pushes under the North American Plate; south of the cape, where the two plates slide 42
Climate change past each other along the San Andreas Fault, the NRC found that the coast is sinking .6 to 3.7 mm/yr (National Research Council, 2012). On closer inspection, however, the picture along Washington’s shores is more complicated and less cheery. The Pacific Plate isn’t just pushing the North American Plate up; it’s tilting it back. Since the 1980s, various observers have noted local variation in Washington’s vertical land movement. New research by Washington Sea Grant and partner organizations clarifies this variation. Nearest to the fault, the Olympic Peninsula’s northwest corner is indeed rising, by about 2.6 mm/yr, possibly enough to outpace sea-level rise in the near term (unless a major offshore earthquake suddenly drops Neah Bay a meter lower, as anticipated some day). Seventy miles to the east, Port Angeles is also rising, by what appears to be a little less than a millimeter a year. Farther from the fault the effect quickly drops off and reverses; Friday Harbor is sinking slightly and Port Townsend by about .8 mm/yr. The effect is most pronounced where it will prove most costly, along the densely developed heart of Puget Sound: Seattle appears to be sinking about 1.2 mm/year – enough to add another 4 inches to the sea’s rise before the century is out (Miller et al., 2015). These impacts, and others not discussed here, may not seem quite so severe as the desertification predicted for vast swathes of territory at lower latitudes. But that will be cold comfort for the Puget Sound region as it faces the complexity and sweep of its own climate challenges. References Carrington, E., & Friedman, C. S. (2015). Impacts of Ocean Acidification on Wild and Farmed Mussels in Puget Sound (Year 1 progress report). Washington Sea Grant. Elsner, M. M., Cuo, L., Voisin, N., Deems, J. S., Hamlet, A. F., Vano, J. A., … Lettenmaier, D. P. (2010). Implications of 21st century climate change for the hydrology of Washington State. Climatic Change, 102(1-2), 225–260. http://doi.org/10.1007/s10584-010-9855-0. Glick, P., Clough, J., & Nunley, B. (2007). Sea-level rise and coastal habitats in the Pacific Northwest: An analysis for Puget Sound, southwestern Washington, and northwestern Oregon. National Wildlife Federation. Keister, J., & McElhany, P. (2015). Effects of Ocean Acidification on Trophically-Important Crustacean Zooplankton of Washington State (Final report). Washington Sea Grant. Mass, C. (2014, July 28). Cliff Mass Weather Blog: Will the Pacific Northwest be a Climate Refuge Under Global Warming? Retrieved from http://cliffmass.blogspot.com/2014/07/will-pacific-northwest-be-climate.html. Miller, I., et al (2015). “Localized sea level projections for the coastal communities on the Strait of Juan de Fuca” (draft). 43
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