SYNTHESIS AND EMERGING IDEAS Paradigm shifts in soil organic matter research affect interpretations of aquatic carbon cycling: transcending disciplinary and ecosystem boundaries E. Marı ´n-Spiotta • K. E. Gruley • J. Crawford • E. E. Atkinson • J. R. Miesel • S. Greene • C. Cardona-Correa • R. G. M. Spencer Received: 25 September 2013 / Accepted: 22 December 2013 Ó Springer International Publishing Switzerland 2014 Abstract New conceptual models that highlight the importance of environmental, rather than molecular, controls on soil organic matter affect interpretations of organic matter (OM) persistence across terrestrial and aquatic boundaries. We propose that changing para- digms in our thinking about OM decomposition explain some of the uncertainties surrounding the fate of land-derived carbon (C) in marine environments. Terrestrial OM, which historically has been thought to be chemically recalcitrant to decay in soil and aquatic environments, dominates inputs to rivers yet is found in trace amounts in the ocean. We discuss three major transformations in our understanding of OM persis- tence that influence interpretations of the fate of aquatic OM: (1) a shift away from an emphasis on chemical recalcitrance as a primary predictor of turnover; (2) new interpretations of radiocarbon ages, which affect predictions of reactivity; and (3) the recognition that most OM leaving soils in dissolved form has been microbially processed. The first two explain rapid turnover for terrigenous OM in aquatic ecosystems once it leaves the soil matrix. The third suggests that the presence of terrestrial OM in aquatic ecosystems may be underestimated by the use of plant biomarkers. Whether these mechanisms occur in isolation of each other or in combination, they provide insight into the missing terrestrial C signature in the ocean. Spatially and temporally varying transforma- tions of OM along land–water networks require that common terrestrial source indicators be interpreted within specific environmental contexts. We identify areas of research where collaborations between aquatic and terrestrial scientists will enhance quanti- fication of C transfer from soils to inland water bodies, the ocean, and the atmosphere. Accurate estimates of OM processing are essential for improving predictions Responsible Editor: Cory Cleveland. E. Marı ´n-Spiotta (&) Á K. E. Gruley Á E. E. Atkinson Á S. Greene Department of Geography, University of Wisconsin- Madison, 550 N. Park St., Madison, WI 53706, USA e-mail: marinspiotta@wisc.edu J. Crawford Center for Limnology, University of Wisconsin-Madison, 680 N. Park St., Madison, WI 53706, USA J. Crawford National Research Program, U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303, USA J. R. Miesel Department of Forestry, Michigan State University, 480 Wilson Rd., East Lansing, MI 48824, USA C. Cardona-Correa Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA R. G. M. Spencer Woods Hole Research Center, 149 Woods Hole Rd, Falmouth, MA 02540, USA 123 Biogeochemistry DOI 10.1007/s10533-013-9949-7