Documented pH decline in Coastal Washington and ecosystem implications

PI : Dr. Cathy Pfister


Research Institution: University of Chicago

Phone:  773-834-0071


Project website:


My work in marine ecology has focused on the processes that determine the success of species in the nearshore environment.  I am taxonomically general, but have special affection for seaweeds, invertebrates and fishes.  Through my long-term studies on the outer coast of Washington state, I have developed an appreciation for the combined roles of ocean-driven events to the idiosyncratic effects of particular species interactions.

My concern and expertise in ocean acidification have come about due to the patterns that I have documented at Tatoosh Island in Washington state (collaborative with Tim Wootton) showing: 1. a decline in seawater pH over the past 10 years that is 7 times greater than expected , and 2. a similar decline in the carbon isotope value of the shell material of California mussels over the past decade , 3. the unprecedented stable carbon isotope values recorded by shells now compared with those from previous decades and millennia , 4. the decline in mussel shell thickness from pre-Columbian time to the present .

Current research in my lab related to OA emphasizes both continued seawater monitoring and data collection to link changes in ocean chemistry with in situresponses of ecosystems in nature, using community dynamics data as well as target studies with particular species.  The seawater monitoring that we do is summarized in the table below. The biological monitoring includes Wootton’s continued point censuses and  population count of all organisms in replicated plots in the mussel bed (initiated in 1993, Pfister’s estimates of kelp demography forAlaria nana (since 1997) and Pleurophycus gardneri (since 1991), and tidepool fish recruitment (since 1989).


Seawater parameters collected at Washington sites Shore-based Locales Ship-based Offshore
  Tatoosh Isl 3 sites eastward toward Port Angeles, WA§ All 4 sites 2 km offshore
water nutrients monthly monthly monthly
temperature 10-30 min 10 min monthly
pH, DO,chl a,  sal 30 min opportunistically monthly
spectrophotometric pH ~10 d/month    
pCO2, TA (Scripps) ~6 d/month   monthly
(48.32,-124.74),§Second Beach(48.37,-124.40),Slip Point(48.26,-124.25),Observatory Pt(48.26,-124.25)


We are further targeting several species where we can analyze historical versus modern indicators of the environment.  For example, my graduate student, Sophie McCoy, is repeating the identical experimental analysis of crustose coralline algal growth and species interactions on Tatoosh that R. T. Paine did in the early 1980s, while supplementing these with pCO manipulations at the Shedd Aquarium in Chicago.  Nanxi Bian, a geophysical sciences student, is further developing high resolution stable isotope sampling, and using Laser Ablation ICP-MS to look for elemental changes in mussel shells over decades and millenia, and their relationships to contemporary pH change.

My work through the years has been made possible by funding from the NSF, the Mellon Foundation, and the SeaDoc Foundation.  The Makah Tribal Nation has generously allowed access.

Wootton, J. T., C. A. Pfister, J. D. Forester. 2008.Dynamical patterns and ecological impacts of changing ocean pH in a high-resolution multi-year dataset. Proceedings of the National Academy of Sciences 105:18848-18853. Pfister, C. A., S.J. McCoy, J. T. Wootton, P. A. Martin, A. S. Colman, D. Archer. 2011. Rapid environmental change over the past decade revealed by isotopic analysis of the California mussel in the northeast Pacific. PLoS ONE 6(10):e25766. doi:10.1371/journal.pone.0025766. 3Pfister, C. A., K. Roy, , J. T. Wootton, S.J. McCoy, R. T. Paine, , T. H. Suchanek, E. Sanford. submitted ms. Long-term decline in shell calcification of a foundational species in the northeast Pacific Ocean. 

KEY WORDS: pH decline, mussels, Mytilus californianus, carbon isotopes, elemental analysis, long-term research, Tatoosh Island, kelp, decreased calcification, Laser Ablation ICP-MS, crustose coralline algae (CCA )