Temperature-controlled organic carbon mineralization in lake sediments

Abstract

onto the sediments, a certain proportion will be mineralized, and the remainder will be buried over geological timescales. We investigated to what extent a warmer climate will affect OC mineralization and burial in lake sediments. Here we show that the mineralization of OC in lake sediment is strongly positively related to temperature, implying that increased water temperature leads to more mineralization and less burial of OC. For lakes in the boreal zone, assuming that OC delivery to the sediments will be similar to present-day conditions, we estimate that temperature increases according to latest scenarios presented by the Intergovernmental Panel on Climate Change 7 result in a 4-27 % (0.9-6.4 Tg C yr -1 ) decrease in annual OC burial, constituting a positive feedback of aquatic carbon release on climate.Nature 466, 478-481 (22 July 2010) doi:10.1038/nature09186 2 The sequestration of OC in the sediments of inland waters, both natural and man made 8,9,3,10,11 , is comparable to or even higher than in marine sediments 4 and soils 12,13,14,15 . Inland waters do not only bury OC, but are also active sites for the mineralization of considerable amounts of OC, originating from internal production or from the terrestrial environment 4,5,16 . The OC that reaches the lake sediment surface will partly be mineralized to CO 2 or CH 4 by heterotrophic microorganisms, and partly be buried in the sediments. The proportion of the OC buried (i.e., the ratio of OC burial per OC deposition onto the sediment surface) is termed the OC burial efficiency, while the fraction of the sediment OC that is lost through microbial processing is termed OC mineralization. As a consequence, the amount of OC that is eventually buried is a direct function of the burial efficiency 17 . The OC burial efficiency in lake sediments is related to oxygen exposure, but the effect of temperature on OC mineralization and burial remains unclear 17 . Relationships between lake sediment mineralization and temperature proposed so far are subject to confounding factors such as lake depth, OC quality, and lake trophic state 18,19 . In view of anthropogenic global warming and the substantial amount of OC buried in inland water sediments, it is critical to elucidate how temperature affects burial efficiency, to allow assessment of the future role of lakes as carbon sinks.The boreal region contains roughly 30% of the global lakes 20,21 and is rich in OC 22 . Accordingly, boreal lake sediments contain 15% of the total carbon pool of the biome 22 . The Canadian boreal forest region alone could account for more than 10% of the global lake burial 5 . Northern latitudes, including the boreal zone, are expected to experience particularly severe warming 7,23 , suggesting that temperature-dependence of sediment OC burial may be of particular importance at these latitudes.We assessed the relationship between sediment OC mineralization and temperature in a crosssystem survey of boreal lakes in central Sweden, and by compilation of published data from widely different...

Land-use change, not climate, controls organic carbon burial in lakes

“…Although lakes are not normally included in regional terrestrial C budgets [37], they can have a large effect on net ecosystem storage if the rates of either aquatic production or respiration (loss rates) are substantially altered [39]. Evidence from this study indicates that there has been an increase in C sequestration by lakes at the regional scale.…”

Spatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, China

“…Although lakes in the Yangtze floodplain had higher productivity in the water column due to eutrophication , most of them were shallow lakes that were subject to frequent turbulence and resuspension of sediments . In addition, warm-humid climate in the Yangtze floodplain could promote decomposition of POC in the water column and TOC in the sediments (Gudasz et al, 2010), which led to less TOC storage in the surface sediments. On the other hand, lakes in the Yunnan-Guizhou Plateau were deep with higher lake productivity, which had favorable TOC burial conditions (Jiang and Huang, 2004).…”

Magnitude and regulation of bacterioplankton respiratory quotient across freshwater environmental gradients

“…Overall, the contribution of BR to CO 2 efflux was also smaller from ponds and tarns, in comparison to that of the deeper lakes ( Figure 5). In shallow systems, the water column CO 2 and O 2 dynamics are probably dominated by benthic processes (Pace and Prairie, 2005;Gudasz et al, 2010) that take control over the regulation of pCO 2 and O 2 dynamics (Figure 3). However, regardless of the systems considered, there were no significant relationships between RQ and DOC, suggesting that it is not the amount of DOC, but rather its origin and composition that have a major role for the pathways of ecosystem metabolism.…”