1. Spatial and Temporal Variability of pCO2 in the Great Bay Estuary System Chris Hunt, Joe Salisbury, Doug Vandemark, Janet Campbell University of New Hampshire Wade McGillis- Lamont-Doherty Earth Observatory ASLO Session SS07, Santa Fe February 5, 2007

7. 44 km^2 of estuary, 230 km of shoreline Tidally dominated Freshwater typically represents only 2% of tidal prism Tidal height ~2m Observed flushing time is 18 days from head of estuary (during high river flow)

8. ~10 km to Gulf of Maine

9. BasinUrbanAgriculturalForestedWetlandsCleared Bellamy837469 Cocheco1237159 Lamprey11566612 Oyster837549 Salmon Falls11766511 Squamscott9664614 From Oczkowski, A. 2002, ‘Riverine inputs of nutrients to Great Bay, NH (USA)’, MS Thesis, Department of Earth Science, UNH, Durham

10. R/V Camden Belle Fast equilibrator for continuous pCO2 measurements. Flow-through system equipped to measure Fl-Chl, Fl-CDOM, beam attenuation, DO, Temp, and Salinity. Seawater is pumped through the system at a rate of 20L/min.

11. After a drought: Oct 4-6, 2005 After spring runoff: April 7 & 10, 2006 After a historic flood: June 5-6, 2006 During Fall low flow: October 5- 6, 2006

13. Salinity (psu) Oct 05 Apr 06 Jun 06 Oct 06

14. Oct 2005Apr 2006 Jun 2006 Oct 2006

15. pCO2 (uatm) Oct 05 Apr 06 Jun 06 Oct 06

16. TA (umol/kg) Salinity (psu) Slope=57.8 Int=316.3 Conservative mixing line DIC (umol/kg) Salinity (psu) Int=467.3 Slope=46.8 Conservative mixing line, using an abiotic oceanic endmember Conservative pCO2 calculated using carbonate equations from Pilson (1998) and K1 and K2 from Cai and Wang (1998) Cai W.-J. and Wang Y. (1998) The chemistry, fluxes and source of carbon dioxide in the estuarine waters of the Satilla and Altahama Rivers, Georgia. Limnol. Oceanogr. 43, 657-668. Pilson, M.E.Q. (1998). An Introduction to the Chemistry of the Sea. Prentice Hall, Upper Saddle River, New Jersey. CO 2 (f) + H 2 O H 2 CO 3 HCO 3 - + H + CO 3 = + H + K0K0 K1K1 K2K2

17. pCO2 Anomaly= pCO2 conservative – pCO2 observed Values >0 indicate less CO2 than predicted by conservative mixing Values <0 indicate more CO2 than predicted by conservative mixing Values >0 suggest autotrophy Values <0 suggest heterotrophy (uatm) pCO2 Anomaly Oct 05 Apr 06 Jun 06 Oct 06

18. pCO2 Anomaly %= (pCO2 conservative – pCO2 observed ) pCO2 conservative (%) Values >0 indicate less CO2 than predicted by conservative mixing Values <0 indicate more CO2 than predicted by conservative mixing Values >0 suggest autotrophy Values <0 suggest heterotrophy pCO2 Anomaly % Oct 05 Apr 06 Jun 06 Oct 06

19. Conclusions The Great Bay operates as a ‘system of systems’, with differing metabolic patterns We infer that seasonality and climatic events have a dramatic effect upon carbon processing Endmember contributions from rivers seem to strongly influence estuarine biogeochemistry General classification of estuaries as heterotrophic does not describe the Great Bay system, as well as other New England estuaries (e.g. Merrimack River)

20. Speculations River-sourced nutrients, OC, and light limitation drive patterns of heterotrophy/autotrophy in Great Bay Precipitation events move terrestrial labile carbon to the estuary, promoting strong heterotrophy Inputs from municipal WWTF significantly affect estuarine carbon cycle, particularly during low river flow

21. NO3 (umol/L) Oct 2005 Nitrate Oct 2006 Nitrate

22. Future Work Determine seasonal DIC and OC fluxes for system as a whole and individual rivers Calculate net CO2 exchange Use caffeine as an anthropogenic tracer Install continuous CO2 system in Great Bay?