Sources of Acidic Bottom Water in Bellingham Bay, Washington

Western Washington University Western CEDAR

2018 Salish Sea Ecosystem Conference Salish Sea Ecosystem Conference (Seattle, Wash.)

Apr 5th, 10:45 AM - 11:00 AM

Sources of acidic bottom water in Bellingham Bay, Washington

David Shull Western Washington Univ., United States, [email protected]

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Part of the Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, and the Terrestrial and Aquatic Ecology Commons

Shull, David, "Sources of acidic bottom water in Bellingham Bay, Washington" (2018). Salish Sea Ecosystem Conference. 159. https://cedar.wwu.edu/ssec/2018ssec/allsessions/159

This Event is brought to you for free and open access by the Conferences and Events at Western CEDAR. It has been accepted for inclusion in Salish Sea Ecosystem Conference by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. Sources of acidic bottom water in Bellingham Bay Results of research performed by Huxley College undergraduates in the class “Oceanography of the Salish Sea”

David Shull (Huxley College, WWU) and 22 senior undergraduates Shannon Point Marine Center Quantifying Bellingham Bay Carbonate system

• Hydrographic survey • Hydrographic survey. Measure DIC, pH, T, S • Calculate alkalinity and Ωarg using CO2SYS • Water column and sedimentary respiration • Measure water column oxygen consumption rates and calculate DIC input • Measure sedimentary DIC and pH fluxes, calculate alkalinity flux • Other sources of DIC and Alkalinity • Calculate DIC and alkalinity flux from the Nooksack R and from inflowing deep water • Use data on pH, alkalinity, and flow to calculate the DIC and alkalinity flux from the Post-point WWTP • Modeling • Generate box-model of northern Bellingham Bay • Use data from the Bellingham Bay Se’lhaem buoy. Determine the sources of DIC and Alkalinity to Bellingham Bay the cause of corrosive bottom water. Hydrographic survey

• Samples collected by CTD-rosette at 4 sites D

• DIC measured by NDIR C • pH measured by cresol purple absorbance B • Respiration rates • Sediment incubations • Nooksack R samples • WWTP data

A DIC and Alkalinity

A Lowest pH = 7.5

A Lowest Ωarg = 0.5

A -1 -1 Oxygen consumption (µmol L d ) Oxygen consumption (µmol L-1 d-1) Water column respiration (↑DIC, Alkalinity unchanged)

D Stn C C Oxygen consumption (µmol L-1 d-1) Oxygen consumption (µmol L-1 d-1)

Stn B

A DIC and Alkalinity sources to Bellingham Bay Sedimentary processes increase BOTH DIC and Alkalinity Change in DIC in incubated sediment cores Change in alkalinity in incubated sediment cores

2700 2600 2600 2500 2500 2400 2400 2300 2300 2200 2200 DIC (µM) 2100 2100 Alkalinity (µmol) Alkalinity 2000 2000 1900 1900 1800 0 20 40 60 80 100 0 20 40 60 80 100 Incubation Time (hrs) Incubation Time (hrs) DIC and Alkalinity sources to Bellingham Bay: Nooksack River

2500 Dissolved inorganic carbon

2000 ) 1 - 1500

1000 DIC (µmol kg

500

0 Silver Lynden Deming South ForkNorth Fork DIC and Alkalinity sources to Bellingham Bay: Nooksack River

1600 1400 Alkalinity 1)

- 1200 1000 800 600

Alkalinity (µmol kg (µmol Alkalinity 400 200 0 Silver Lynden Deming South Fork North Fork DIC and Alkalinity sources to Bellingham Bay: Nooksack River

7.2 pH 7.1 7 6.9

pH 6.8 6.7 6.6 6.5 6.4 Silver Lynden Deming South Fork North Fork Box model of northern Bellingham Bay pH

Nooksack Se’lhaem Gas River • Measured sources and sinks buoy exchange of DIC and Alkalinity • Calculated change in pH and Photosynthesis Respiration Ωarg in bottom water Outflow • Questions: Mixing Upwelling

• How were pH and Ωarg changing? • What processes create low pH bottom water? Inflow Respiration Sediment fluxes

Box model of northern Bellingham Bay pH

• How were pH and Ωarg changing? • What processes create low pH bottom water? Inflow Respiration Sediment fluxes Box model geometry, measurements

Nooksack R discharge

Surface water pH Bottom water changes in DIC, pH, Alkalinity and Ωarg

DIC and Alkalinity increasing Apr 4-May-4

pH and aragonite saturation decreasing Apr 4-May-4 Modeled changes in DIC, pH, Alkalinity and Ωarg Slower estuarine circulation leads to increased DIC and decreased pH

DeepSurface-water water Salinity: salinity 2017 ) psu ) mM DIC ( Surface Surface water salinity( Modeled changes in DIC, pH, Alkalinity and Ωarg Water column respiration drives the decline in pH and aragonite saturation

With respiration Without respiration With respiration Without respiration Modeled changes in DIC, pH, Alkalinity and Ωarg Sedimentary alkalinity flux drives the change in bottom water alkalinity Sources of acidic water in Bellingham Bay

• Bottom water pH and Ωarg are low compared to elsewhere in Puget Sound • Water column and sedimentary respiration drive declining pH • Water column respiration increases DIC but not alkalinity • Sedimentary processes supply BOTH DIC and alkalinity • Bottom water acidity likely varies seasonally • The rate of mean circulation in the bay (and thus bottom water residence time) also contributes to low pH. • Reduced Nooksack R flow in summer (predicted by regional climate models) along with increasing atmospheric CO2 will lead to future declines in bottom water pH and Ωarg Thanks to

• ESCI 491 – Oceanography of the Salish Sea Zach Barker, Nick Bartish, Nilza Chodon, Kastin Ellis, Kristen Fagerstrom, Kaya Fletcher, Shay Hengen, Saraanne Inglin, Alice Lazzar- Atwood, Amanda MacFadden, Stephan, Neu-Yagle, Cecily Ofstad, Gina O’Kelley, Jackson Osborn, Mark Quick, Lauchlan Ray, Talulah Corrina, Ben Smith, Jayme Street, Nick Sturman, Nick Tedford, Gabby Whitehall • Brooke Love and Kelly Bright (WWU) • UW Applied Physics Laboratory – Thanks for the buoy!