Aquatic carbon cycling in the conterminous United States and implications for terrestrial carbon accounting

Proceedings of the National Academy of Sciences of the United States of America
By: , and 

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Abstract

Inland water ecosystems dynamically process, transport, and sequester carbon. However, the transport of carbon through aquatic environments has not been quantitatively integrated in the context of terrestrial ecosystems. Here, we present the first integrated assessment, to our knowledge, of freshwater carbon fluxes for the conterminous United States, where 106 (range: 71–149) teragrams of carbon per year (TgC⋅y−1) is exported downstream or emitted to the atmosphere and sedimentation stores 21 (range: 9–65) TgC⋅y−1 in lakes and reservoirs. We show that there is significant regional variation in aquatic carbon flux, but verify that emission across stream and river surfaces represents the dominant flux at 69 (range: 36–110) TgC⋅y−1 or 65% of the total aquatic carbon flux for the conterminous United States. Comparing our results with the output of a suite of terrestrial biosphere models (TBMs), we suggest that within the current modeling framework, calculations of net ecosystem production (NEP) defined as terrestrial only may be overestimated by as much as 27%. However, the internal production and mineralization of carbon in freshwaters remain to be quantified and would reduce the effect of including aquatic carbon fluxes within calculations of terrestrial NEP. Reconciliation of carbon mass–flux interactions between terrestrial and aquatic carbon sources and sinks will require significant additional research and modeling capacity.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Aquatic carbon cycling in the conterminous United States and implications for terrestrial carbon accounting
Series title Proceedings of the National Academy of Sciences of the United States of America
DOI 10.1073/pnas.1512651112
Volume 113
Issue 1
Year Published 2016
Language English
Publisher PNAS
Contributing office(s) National Research Program - Central Branch
Description 6 p.
First page 58
Last page 63