Dissolved Gas Concentrations in Two Reservoir Systems Kyle Hacker, Christopher Whitney, Drew Robison, Wilfred Wollheim Introduction/Background Methods Comparing the gas concentrations at the Reservoir and Beaver Pond across macrophyte species Conclusion Literature Cited Acknowledgements – This research was supported with funding from the National Science Foundation’s grant to NH EPSCoR (ENG ). Lakes, streams, and reservoirs are often net sources of carbon and methane to the atmosphere and are important to consider in continental scale carbon cycling (Cole et al. 2007, Bastviken et al. 2011) As both carbon dioxide (CO 2 )and methane (CH 4 )are harmful greenhouse gases, it is important for studies to quantify the amount of greenhouse gases emitted by these systems. The shallow waters of these systems are populated by large aquatic plants known as macrophytes. The effect of macrophytes on gas emissions depends on a variety of factors, including the morphology of the plant. For example, emergent, leaved plants can deplete oxygen levels because oxygen is released to the atmosphere whereas rooted, submerged plants can pump oxygen into the water column and sediments (Caraco et al. 2006). Sample locations were chosen based on species of macrophyte bed present. Within the Ipswich reservoir, there were three prevailing macrophyte beds, Pondweed, Millfoil, and Lilly with lily being the most dominant. There were 2 Pondweed and Millfoil sites and 3 lily and open water sites. At the beaver pond, there was only one dominant macrophyte bed, Pickerel weed. There were 3 pickerel weed sites and 3 open water sites at the CCBP. Once the locations were chosen, gas samples were taken at the surface and at depth using syringes. Tygon tubing was attached to a syringe and fed through a pvc pipe to submerge and gather the samples at depth. Nutrient grab samples were also collected and filtered in the field. DO, Conductivity and water temperature were measured using a YSI Do probe and a conductivity probe. Samples were gathered at the Reservoir twice this summer and once at the beaver pond. Average CO 2 increases and average DO decreases with depth at all locations likely due to respiration within the sediment. This is not consistent for methane The submerged macrophytes in this study do not exhibit patterns consistent with elevated DO concentrations at depth. Of the four macrophyte beds, pondweed exhibited the highest DO concentration at depth while Millfoil exhibited the lowest. While DIC is comparable between the two locations, surface DO is lower at Cart Creek and CH 4 is significantly higher as well. The relatively high CH 4 concentration at Cart Creek suggests that the system acts more like a wetland than the Ipswich reservoir as CH 4 production is common characteristic of wetlands. Further study could be done to better highlight the relationship between macrophyte species and gas concentration in reservoir systems. For example, more study locations would allow for a comparison of systems with a broader range of hydrologic conditions With the removal of the dam expected in the summer of 2017, this data provides a baseline to compare gas concentrations within the water column pre and post dam removal Approximate a) Ipswich reservoir (SMD) sampling locations and b) Cart Creek beaver pond (CCBP) sampling locations Cart CreekSouth Middleton Dissolved oxygen decreases with depth. The average DO concentrations at the beaver pond are similar to the DO concentrations at depth within the reservoir. Average DIC increases with depth at all reservoir locations. DIC in the beaver pond is relatively high Methane concentrations are significantly higher at the beaver pond than in the reservoir. There is no significant relationship between macrophyte biomass and vertical DO concentration gradient. This is also true for DIC (r 2 < 0.01, p =0.86) and CH 4 (r 2 = 0.02, p= 0.62) Questions Do macrophyte beds alter gas concentrations within the water column? How do emergent vs. submerged macrophytes affect the concentrations of these gases? How do the gas concentrations differ between the Ipswich reservoir and the Cart Creek beaver pond? Hypothesis There will be low oxygen and high CO 2 levels in the water near emergent macrophyte beds relative to submerged macrophyte beds. Although oxygen concentration within the water will be lower, methane concentration will remain low due to low organic carbon inputs. Cole, J. J., Prairie, Y. T., Caraco, N. F., Mcdowell, W. H., Tranvik, L. J., Striegl, R. G.,... Melack, J. (2007). Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget. Ecosystems, 10(1), doi: /s Caraco, N., Cole, J., Findlay, S., & Wigand, C. (2006). Vascular Plants as Engineers of Oxygen in Aquatic Systems. BioScience, 56(3), 219. doi: / (2006)056[0219:vpaeoo]2.0.co;2 Bastviken, D., Tranvik, L. J., Downing, J. A., Crill, P. M., & Enrich-Prast, A. (2011). Freshwater Methane Emissions Offset the Continental Carbon Sink. Science, 331(6013), doi: /science