Examining the influence of land use and flow variability on carbon emissions from headwater streams

River networks contribute significantly to global carbon (C) and greenhouse gas budgets. Most streams and rivers are supersaturated with carbon dioxide (CO₂) and methane (CH₄), making lotic ecosystems hotspots of C emissions at regional and global scales. While recent investigations have begun to incorporate aquatic systems into continental C budgets, our understanding of what drives the variability in space and time of these dynamics is poorly constrained. To address these uncertainties, we have installed high frequency dissolved CO₂ sensors to study the effects of land use and flow variability on CO₂ dynamics in four headwater streams of differing land use in New England. We have also installed bubble traps at two of these sites to examine the contribution of ebullition to CH₄ and CO₂ fluxes. The influence of discharge on CO₂ emissions will be analyzed through effective discharge and hysteretic analyses, providing quantitative comparisons between sites and across time. Metabolism estimates, made using the single-station open-water oxygen exchange approach and streamMetabolizer, allow for the partitioning of aquatic and terrestrially derived CO₂. Ebullitive fluxes of CO₂ and CH₄ will be examined in relation to sediment characteristics and flow events. Comparison of these analyses across sites will reveal how land use influences CO₂ loading to streams, the internal production of CO₂ and CH₄, and the relationship between flow and carbon emissions. Through this study we will gain a better understanding of the factors controlling C delivery to and processing within river networks in the context of changing climatic patterns and land use.