Inland Waters

Human impacts on carbon movement and processing in inland waters include 1) land-use change that promotes the destabilization of soil carbon and increases erosion (Lal and Pimentel 2008; Quinton et al., 2010; Stallard 1998); 2) altered climate patterns that shift the timing and magnitude of precipitation and hydrological events (Clair and Ehrman 1996; Evans et al., 2007); 3) changes in nutrient and organic matter inputs that alter carbon processing and storage within aquatic environments (Humborg et al., 2004; Mayorga et al., 2010; Seitzinger et al., 2005); and 4) changes in temperature (Nelson and Palmer 2007). These effects are not independent of one another. However, inland waters are inherently difficult to evaluate in the context of carbon management, from either a sequestration or mitigation position. In contrast to forested ecosystems, the chemistry of inland waters changes rapidly on timescales from seconds to days in direct relation to the hydrological regime (Sobczak and Raymond 2015). Furthermore, the sources of carbon within inland waters are poorly characterized across spatial and temporal scales relevant to national-scale management decisions. A robust understanding of the impact that dams have on carbon transformation and fluxes to coastal systems would directly identify the connections between anthropogenic energy and water resource needs and the carbon cycling of inland waters (Deemer et al., 2016; Maeck et al., 2014; Teodoru et al., 2012). The research community is currently unable to identify whether all dammed systems cause increased carbon emissions, but recent synthesis efforts suggest that CO₂ and CH₄ emissions increase under conditions of high nutrients and with large inputs of terrestrial carbon (Barros et al., 2011; Deemer et al., 2016; Teodoru et al., 2012). Worldwide there are more than 1 million estimated dams (Lehner et al., 2011); of these, over 87,000 have heights >15 m (World Commission on Dams 2000). Research is needed to evaluate the impact that this level of damming has on the aquatic carbon cycle.