OA in the Bay! Studying the impacts of oyster shell application on pH in Great Bay Jennifer J. Halstead1 Advisor: Christopher R. Peter2 1: Marine, Estuarine, and Freshwater Biology. COLSA. UNH 2: Jackson Estuarine Laboratory. UNH. Introduction Ocean and coastal acidification are growing concerns as atmospheric carbon dioxide levels continue to rise. When CO2 reacts with water, changes in the carbonate system impact the ability of calcifying organisms to grow and survive. Local oyster restoration efforts could have the potential to mitigate the impacts of acidification in Great Bay. Results I. Historical Conclusions I. Historical As water warms in June, changes in pH would be seen, and the more stable water temperatures in July would aid in pH stabilization (Gledhill, et.al., 2015). Hypothesis: As atmospheric CO2 levels continue to rise, diurnal pH variations will become more drastic. Results: Historic diurnal pH variations showed significant difference during the month of June but not during the month of July. Figure 6: Ulva spp. growing from the intake pipe in the oyster tank. II. Mesocosm Additional biological productivity or respiration could impact the pH in the tank as well (Gledhill, et. al., 2015) Activity would respond to different flow scenarios Ulva spp. and diatoms were in much higher abundance in the shell tank vs. the control tank. June July t ratio -2.14 -1.01 prob >t 0.0426 0.1794 Figure 1: Oyster shell from experimental Mesocosm tank. II. Mesocosm Figure 2: Great Bay, NH. Project Elements I. Historical Analyzed changes of pH in Great Bay from 2005 to 2010 during June and July II. Mesocosm Flow-through mesocosms (Control & Oyster shell), exposed to 3 different flow rates Localized impacts of whole oyster shell application III. Continual In situ Monitoring pH monitored at 2 sites on Adams Point (natural and artificial reef), alternating between bottom and surface measurements IV. Spot In situ Monitoring Sonde deployed at a natural reef near Nannie’s Island for 2 weeks III. Continual In situ Monitoring Hypothesis: A localized impact of oyster shell dissolution will be seen over an oyster reef when compared to surface waters. Results: No significant difference between surface and bottom measurements or reef type. These results are reflective of Great Bay being a well-mixed estuary (Brown and Arellano, 1980). Figure 7: Ulvalactuca and oyster shell at JEL pier sample site. t ratio 1.737 prob >t 0.2061 Figure 8: Nannie’s Island, Great Bay, NH. t ratio 1.487 prob >t 0.243 t ratio 0.577 prob >t 0.462 IV. Spot In situ Monitoring Changes in pH and the carbonate system can occur in response to tidal, light, temperature, and nutrient changes. Changes such as this could be incorporated into future restoration location decisions. Reefs with adult oysters also provide a filtration capacity that could aid in pH stabilization. Figure 9: Data collection sonde upon recovery Hypothesis: If shell dissolution is occurring, a buffering capacity will be seen and the pH in the experimental tank will be higher than the control tank. Results: Inconclusive. III. Continual In situ Monitoring Future recommendations Building off the Mesocosm experiment by controlling biological variables; covers that shield the tanks from light would limit effects of algae on pH. IV. Spot In situ Monitoring Figure 3: A mass of diatoms in the Mesocosm control tank. Figure 4: Exiting the water at Adam’s Point South field location. Figure 5: YSI probe sits on the bottom of the experimental tank on top of oyster shell. Site-Depth t ratio 0.0122 prob >t 0.998 References Brown, W.S. & Arellano, E. Estuaries (1980) 3: 248. doi:10.2307/1352080 Gledhill, D.K. et al. 2015. Ocean and coastal acidification off New England and Nova Scotia. Oceanography 28(2):182–197, http://dx.doi.org/10.5670/oceanog.2015.41 Acknowledgements: This work was supported in part by an award from the National Science Foundation (NSF #1101245) and by the Provost of the University of New Hampshire. We would also like to acknowledge the contributions of all involved in any or all parts of this project including Ray Grizzle, Krystin Ward, Tom Gregory, Dave Shay, Larry Harris, Gregg Moore.