Carbon in Rivers: a Global Perspective

     As the main pathway for the ultimate preservation of terrigenous production in modern environments, the transfer of organic matter from the land to the oceans via fluvial systems is a key link in the global carbon cycle (Ittekot and Haake 1990; Degens et al. 1991; Hedges et al 1992). Hence, the "role" of rivers in the global carbon cycle is most typically expressed as the fluvial export of total organic and dissolved inorganic carbon from land to the ocean (e.g., Likens et al. 1981).

     Within the overall "role" of river systems, an emerging issue is the importance of dissolved CO2 (Richey et al 2002). The partial pressure of carbon dioxide dissolved in river water (pCO2) represents a deceptively simple expression of the coupling of the water and carbon cycles between terrestrial and fluvial environments. The distribution of pCO2 across a river basin is a function of a long sequence of complex biological and weathering processes and interactions, reflecting both internal carbon dynamics and external biogeochemical processes in upstream terrestrial ecosystems. The downstream expression of this coupling is the amount of organic matter and dissolved inorganic carbon mobilized to and through a river system, augmented by in-stream or riparian primary production and respiration. Perhaps the most evocative aspect of pCO2 is that it is almost always present at concentrations much greater than the atmosphere (that is, it is supersaturated). The question is why, and what are the implications?

     Our  projects represent a combination of field work and modeling.