Modeled Multiple acid pathways in Casco Bay: Implications for the next 25 years J. Salisbury, D. Vandemark, C. Hunt, S. Shellito - Background - Multiple acid pathways into Casco Bay
- Recent observations - Implications for the near future 8.30.4 PgC/yr 90% 4.30.1 PgC/yr 46%
1.00.5 PgC/yr 10% + 2.60.8 PgC/yr 28%
Calculated as the residual of all other flux components 26% 2.50.5 PgC/yr Source: Le Qur et al. 2012; Global Carbon Project 2012 4 CO2 + H2O
CO2 + CO32- + H2O carbonate ions Carbonic acid reduces H2CO3 ocean pH. carbonic acid 2HCO3
bicarbonate ions The concentration of carbonate ions decreases. 5
cmore.soest.hawaii.edu Saturation Index ()) of the mineral aragonite )Ca2+] [CO32-] )> 1 animals can make shell )>>1 easier to make shell )< 1 shell dissolves
sp by temperature: Temp corresponds to . Affected Varies with CO2: CO2 corresponds to . Varies with pH: pH corresponds to . Note: <1.6 may be a threshold for optimal larval growth in clams and oysters (Barton et al, 2012; Salisbury et al, 2008).
carbon dioxide pH Changin g Seawate r Chemist ry
IPCC 2014 WG1, Chapter 3 Doney et al. Ann. Rev. Mar. Sci. 2009 Dore et al. PNAS 2009 Other pathways for acidification Coastal and Estuarine Acidification River water freshens the coast
and alters its ability to buffer against acid pH (NBS scale) Omega ()) in the Kennebec Plume (56 cruises) Data from USGS Waldbusser and Salisbury, 2014 Precipitation is increasing, making the coastal ocean a bit fresher
and more poorly buffered against pH and is likely to continue over the next 25 years (Rawlins et al, 2015) Change in Precipitation Patterns: Intense precipitation events (the heaviest 1 percent) in the continental U.S. from 1958 to 2012. Image Credit: Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens, P. Thorne, R. Vose, M. Wehner, J. Willis, D. Anderson, S. Doney, R. Feely, P. Hennon, V. Kharin, T. Knutson, F. Landerer, T. Lenton, J. Kennedy, and R. Somerville, 2014: Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 19-67. doi:10.7930/J0KW5CXT
Nutrient enhanced acidification Oxygen + decomposing plant matter CO2 + H2O acid How does this affect Casco Bay? Improving or declining? Recent observations and their implications for the near future
pH in Casco Bay (April-October) 8.3 8.2 pH (Total Scale) 8.1
8 7.9 7.8 7.7 7.6 Apr
May Jun Jul Aug Month 2015
Sep Oct Nov Possible difficulty making shell material below 1.5
So far, weve observed 34 of 150 days at <1.5 now freshen the coast on average by 1 salinity unit (1:31) Given a similar time series, we would likely experience 58 days at <1.5 now freshen plus add in the expected CO2 increase over the next 25 years (red) In this scenario we could experience 89 days at <1.5
Concluding remarks: Slow atmospheric acidification Coastal variability can put organisms beyond certain thresholds Casco Bay sensitive to OA from multiple pathways and may be changing quickly But we need to know a lot more about how drivers amplify or dampen OA
