Click Here for Full Article Climate‐dependent CO 2 emissions from lakes Sarian Kosten, 1 Fábio Roland, 2 David M. L. Da Motta Marques, 3 Egbert H. Van Nes, 1 Néstor Mazzeo, 4 Leonel da S. L. Sternberg, 5 Marten Scheffer, 1 and Jon J. Cole 6 Received 24 June 2009; revised 20 December 2009; accepted 28 December 2009; published 8 May 2010. [1] Inland waters, just as the world’s oceans, play an important role in the global carbon cycle. While lakes and reservoirs typically emit CO 2 , they also bury carbon in their sediment. The net CO 2 emission is largely the result of the decomposition or preservation of terrestrially supplied carbon. What regulates the balance between CO 2 emission and carbon burial is not known, but climate change and temperature have been hypothesized to influence both processes. We analyzed patterns in carbon dioxide partial pressure (pCO 2 ) in 83 shallow lakes over a large climatic gradient in South America and found a strong, positive correlation with temperature. The higher pCO 2 in warmer lakes may be caused by a higher, temperature‐dependent mineralization of organic carbon. This pattern suggests that cool lakes may start to emit more CO 2 when they warm up because of climate change. Citation: Kosten, S., F. Roland, D. M. L. Da Motta Marques, E. H. Van Nes, N. Mazzeo, L. da. S. L. Sternberg, M. Scheffer, and J. J. Cole (2010), Climate‐dependent CO 2 emissions from lakes, Global Biogeochem. Cycles, 24, GB2007, doi:10.1029/2009GB003618. 1. Introduction [2] The importance of the world’s oceans in global carbon cycling is well known and their influence on atmospheric CO 2 concentrations is explicitly incorporated in climate change models [Intergovernmental Panel on Climate Change (IPCC), 2007]. So far, however, the role of inland waters has received less attention even though recent studies indicate that they play an important role in regulating carbon fluxes as well [Cole et al., 2007; Downing et al., 2008; Duarte et al., 2008]. A significant part of the organic carbon initially sequestered as CO 2 by terrestrial ecosystems ends up in rivers and lakes. Only about half of this carbon is trans- ported to the oceans [Cole et al., 2007]. Much of the ter- restrially produced carbon entering inland waters is buried in sediments or emitted as CO 2 to the atmosphere [Cole et al., 2007]. In addition, primary production within inland waters represents a substantial carbon flux, especially in lakes with high concentrations of nutrients allowing high productivity [Williamson et al., 2009]. This turns inland waters into carbon processing hot spots in terrestrial landscapes and despite the fact that inland waters occupy a relatively small fraction of the Earth’s surface, they play an important role in the global carbon cycle by processing large amounts of terrestrially derived carbon [Battin et al., 2009]. Depending on the balance between processes such as respiration, pri- mary production, groundwater carbon inflow and calcite precipitation, these systems may be carbon sinks, or become supersaturated with CO 2 and act as CO 2 sources to the atmosphere [Cole et al., 1994, 2000; Duarte and Prairie, 2005; Sobek et al., 2005]. All these processes are likely sensitive to changes in temperature and hydrology. [3] Very little is known about the overall effects of climatic change on the carbon cycling in inland waters. Temperature, for example, may affect carbon cycles in a direct way through its influence on aquatic respiration [Sand‐Jensen et al., 2007] and primary production [Flanagan et al., 2003], which may be most evident when it coincides with an increase in nutrient loading [Christoffersen et al., 2006]. A differential temper- ature dependence of respiration and photosynthesis may lead to a decrease in carbon fixation and an increase in carbon emission [Lopez‐Urrutia et al., 2006]. Altered precipitation regimes may influence lakes’ metabolism as well. For instance through its effect on the hydraulic residence time, which can have several effects including altering carbon sedimentation and mineralization [Algesten et al., 2004; Curtis, 1998]; changing terrestrial inputs of nutrients and organic matter, and possibly primary production as well [Reynolds, 1994; Schallenberg and Burns, 1997]. Temper- ature and precipitation also have an indirect effect on lake’s carbon cycle through their influence on terrestrial carbon fixation and the subsequent carbon leaching to the lake [Sobek et al., 2005]. 1 Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen, Netherlands. 2 Laboratory of Aquatic Ecology, Institute of Biology, Federal University of Juiz de Fora, Juiz de Fora, Brazil. 3 Instituto de Pesquisas Hidra´ ulicas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. 4 Laboratorio de Ecologı´a y rehabilitacı´on de sistemas acua´ticos, Facultad de Ciencias and CURE, Universidad de la República, Montevideo, Uruguay. 5 Department of Biology, University of Miami, Coral Gables, Florida, USA. 6 Cary Institute of Ecosystem Studies, Millbrook, New York, USA. Copyright 2010 by the American Geophysical Union. 0886‐6236/10/2009GB003618 GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 24, GB2007, doi:10.1029/2009GB003618, 2010 GB2007 1 of 7