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A synoptic survey of microbial respiration, organic matter decomposition, and carbon efflux in U.S. streams and rivers
Citation:
Hill, B., C. Elonen, A. Herlihy, T. Jicha, AND R. Mitchell. A synoptic survey of microbial respiration, organic matter decomposition, and carbon efflux in U.S. streams and rivers. Limnology and Oceanography Bulletin. American Society of Limnology and Oceanography, Lawrence, KS, 62(1):S147-S159, (2017).
Impact/Purpose:
• We analyzed microbial respiration and ecoenzyme activities related to organic matter processing in 1879 streams and rivers across the continental US as part of the USEPA’s 2008-2009 National Rivers and Streams Assessment. • Ecoenzymatic stoichiometry was used to construct models for carbon use efficiency (CUE) and decomposition (-k). • The streams and rivers were classified by size (headwaters: 1st-order; streams: 2nd-3rd order; small rivers: 4th-5th order; big rivers 6th-7th order; and great rivers > 8th order), and were grouped into nine national ecoregions. • There were significant ecoregion and stream size effects in the unbalanced, nested analysis of variance of the microbial variables, with organic matter decomposition and modeled microbial respiration increasing from the eastern ecoregions, through the plains ecoregions, to the western ecoregions. • These same microbial measures decreased with increasing streams size. • Microbial respiration estimated from sediment organic carbon stocks and enzyme decomposition models and extrapolated to the ecoregional and national scales suggests that microbes account for 17% of the total CO2 outgassing, and 60% of the aquatic metabolism C losses, from US streams and rivers.
Description:
We analyzed microbial respiration and ecoenzyme activities related to organic matter processing in 1879 streams and rivers across the continental US as part of the USEPA’s 2008-2009 National Rivers and Streams Assessment. Ecoenzymatic stoichiometry was used to construct models for carbon use efficiency (CUE) and decomposition (-k). The streams and rivers were classified by size (headwaters: 1st-order; streams: 2nd-3rd order; small rivers: 4th-5th order; big rivers 6th-7th order; and great rivers > 8th order), and were grouped into nine national ecoregions. The streams and their catchments represented gradients in catchment land cover, channel sediments, and sediment chemistry against which microbial respiration, carbon use efficiency and organic matter decomposition were compared. There were significant ecoregion and stream size effects in the unbalanced, nested analysis of variance of the microbial variables, with organic matter decomposition and modeled microbial respiration increasing from the eastern ecoregions, through the plains ecoregions, to the western ecoregions. These same microbial measures decreased with increasing streams size. Microbial respiration, CUE, and -k were correlated with water and sediment chemistry; CUE and -k were also correlated with stream bed fine sediments; and CUE was further correlated with catchment land cover. Microbial respiration estimated from sediment organic carbon stocks and enzyme decomposition models and extrapolated to the ecoregional and national scales suggests that microbes account for 17% of the total CO2 outgassing, and 60% of the aquatic metabolism C losses, from US streams and rivers.
