Luke C. Loken Emily H. Stanley Edward G. Stets Mark M. Dornblaser Robert G. Striegl John T. Crawford 2016 <p><span>The Upper Mississippi River, engineered for river navigation in the 1930s, includes a series of low-head dams and navigation pools receiving elevated sediment and nutrient loads from the mostly agricultural basin. Using high-resolution, spatially resolved water quality sensor measurements along 1385 river kilometers, we show that primary productivity and organic matter accumulation affect river carbon dioxide and methane emissions to the atmosphere. Phytoplankton drive CO</span>₂<span>to near or below atmospheric equilibrium during the growing season, while anaerobic carbon oxidation supports a large proportion of the CO</span>₂<span> and CH</span>₄<span> production. Reductions of suspended sediment load, absent of dramatic reductions in nutrients, will likely further reduce net CO</span>₂<span>emissions from the river. Large river pools, like Lake Pepin, which removes the majority of upstream sediments, and large agricultural tributaries downstream that deliver significant quantities of sediments and nutrients, are likely to persist as major geographical drivers of greenhouse gas emissions.</span></p> application/pdf 10.1002/2015GL067599 en AGU Publications Basin scale controls on CO₂ and CH₄ emissions from the Upper Mississippi River article