Carbon dioxide efflux in streams and rivers in Upstate New York

Carbon dioxide is an important greenhouse gas that has regulated earth's global temperature for eons. Due to anthropogenic causes, carbon dioxide has shown a rapid increase in the atmosphere resulting in the current observed rise in atmospheric temperature and other climate change phenomena. The importance of understanding and monitoring the carbon cycle, including tracking fluxes from sinks and sources to predict future changes in atmospheric CO₂ concentrations cannot be overstated. It wasn't until the 1980s, however, that the importance of freshwater ecosystems in the carbon cycle was investigated. Although inland freshwater constitutes a small percentage of the exposed water on Earth, it acts as a surprisingly large carbon sink, and perhaps carbon source. In essence, freshwater streams act as conduits of carbon dioxide from land to the sea and atmosphere. This important pipeline is easily influenced by land use changes because carbon dioxide from soil respiration enters streams through baseflow, which is disrupted through changes in the land that comprises watersheds. 
In this study, the carbon dioxide concentrations in urban and rural streams are compared to determine whether local streams are a source or a sink of CO₂ and how CO₂ concentration is affected by land use change. Water samples from a total of 50 streams were obtained during the summer of 2019. In addition, we also obtained weekly water samples from the Hans Groot's Kill during the summer and throughout the Fall and Winter. CO₂ concentrations in all but two rural streams were higher than atmospheric concentrations, indicating they act as a source to the atmosphere. On average, streams had about five times the atmospheric concentration. Rural streams had significantly lower CO₂ concentrations (average = 1808, n = 35) compared to urban streams (average = 2828, n = 25). These data will be compared with alkalinity, pH, DIC concentrations, DIC carbon isotopic composition and ion concentrations to further unravel the biogeochemistry of aquatic CO2. As the global population exceeds 50% in urban areas, and temperatures continue to increase, it is vital that we understand how urbanization and climate change will alter the role freshwater streams and rivers play in the global carbon cycle.