Carbon and Nutrients

Carbon and Nutrients Image

Carbon in World Rivers

Recent research rejects the traditional perspective that rivers are simply passive pipes exporting material to the ocean. In fact, processes occurring in rivers play a critical role transporting and recycling carbon and nutrients, not only within watersheds but also in marine receiving waters. This paradigm shift results from new knowledge that rivers and other inland waters outgas immense quantities of CO2 to the atmosphere (Richey et al 2002; Butman and Raymond, 2011). Globally, inland waters process, transport and bury 2.7 Pg C y-1, roughly equal to the current estimate of the terrestrial sink for anthropogenic C (Battin et al., 2009; Tranvik et al., 2009; Canadell et al., 2007). If these numbers are correct, carbon cycling in rivers essentially relocates and/or mitigates almost all the annual terrestrial sequestration. Depending on the magnitude of these riverine fluxes, the global terrestrial CO2 sink may prove to be smaller than presently estimated because rivers may be mobilizing and remineralizing a significant component of the pool that is currently considered to be sequestered in soils. This astounding observation, developed by several research groups using independent lines of evidence, is under appreciated by the larger research community. Significant effort is required to solidify the science behind these estimates (Melack, 2011).

The Universtiy of Washington team and their regional colleages conducted a series of expeditons over the last decade in the Mekong River system. The story emerging from this work is summarized here, as Mekong River Carbon.