Ocean acidification in Puget Sound was first observed by the shellfish industry. Larval mortalities in select hatcheries and natural set failures in Hood Canal and Willapa Bay over the past five years have created growing alarm over the potential effects of corrosive seawater. Studies reveal that seasonal upwelling of deep oceanic waters is bringing carbon-rich, low pH water to the surface, which may be adversely affecting molluscan bivalve larvae reared in hatchery facilities. This raises larger questions about whether or not chemical changes in seawater are affecting natural populations of shellfish as well. To investigate this further, the Puget Sound Partnership awarded a grant to PSRF, NOAA, UW, PSI and Baywater, Inc. to establish index stations at two important shellfish growing areas in Puget Sound– Big Cove, Totten Inlet in southern Puget Sound and Dabob Bay in Hood Canal. Weekly samples of seawater, spatfall, and planktonic larvae collected at these locations are correlated with oceanographic sampling measuring dissolved inorganic carbon (DIC) total alkalinity (TA), pH, carbonate ion concentration, and aragonite saturation state for the water column. Finding a direct cause and effect will be tricky, to say the least, since shellfish recruitment is a notoriously variable phenomenon. However, if field data shows that during periods of measurably low pH, high densities of setting larvae fail to translate into high recruitment, then there may be a close association between the two. The ocean acidification monitoring program is intended as a long-term study, pending additional funding.
Effects of Ocean Acidification
Adverse effects of corrosive seawater on bivalve populations have potential wide-ranging effects.
- Shellfish production in the South Sound has long played an important role in local economies.
- Natural and cultivated shellfish populations throughout the South Sound provide filtration and nutrient cycling services that are particularly helpful in combating increased nutrient pollution associated with a growing human population.
- Remnant populations of native oysters in Totten and Case Inlets support efforts to rebuild sustainable populations of native oysters elsewhere in South Sound.
All of this – shellfish production, natural filtration, and ecological restoration – may be affected by increasingly corrosive water. And eventually, this would touch each of us in the form of fewer locally grown shellfish, increasingly eutrophic waters and troubled local economies. The need to reduce global CO2 emissions takes on new meaning in the face of these local possibilities.
What is Ocean Acidification?
As the carbon dioxide levels increase in the atmosphere, more and more carbon is being absorbed by marine waters. In fact, about one third of the carbon in the atmosphere gets absorbed by the ocean. When CO2 and saltwater mix, a carbonic acid is created which lowers the pH of seawater and reduces the amount of necessary carbonate ions many marine animals like oysters and clams rely upon to build their shells. The increasing acidification of ocean waters can have widespread effects from altering the marine food web to impacting local economies. PSRF is working with NOAA, University of Washington, Pacific Shellfish Institute, Baywayter, Inc. and Taylor Shellfish to investigate the local implications of ocean acidification on shellfish populations. Weekly samples of seawater and shellfish and plankton larvae collected in Totten Inlet and Dabob Bay are correlated with other oceanographic measurements including dissolved inorganic carbon, alkalinity, and pH. The goal of this project is to better understand the link between ocean acidification and shellfish reproduction in Puget Sound.