Estimating modern carbon burial rates in lakes using a single sediment sample

Abstract

The rate of organic carbon (OC) burial in inland waters is an important flux in the global C-cycle. Here we provide methodological improvements that offer a rapid and accurate assessment of modern OC burial rates in lakes from a single surface-sediment sample. Using a 93 lake dataset of reliably dated sediment cores (OC burial of 9 to 318 g m -2 y -1 ), we demonstrate the applicability of this approach in a variety of lake types. We validate our estimated rates of OC burial against (1) measured whole-lake accumulation from the sum of multiple area-weighted sediment cores, (2) single central-basin cores adjusted for sediment focusing, and (3) duplicate sediment cores taken in multiple locations and at different times (4-10 years apart) in 9 lakes. Our single-sample estimates, which were in good agreement with measured values, suggest a within-lake variability of 4 g m -2 y -1 and have a small inter-lake error of only 6.5%. The applicability of this approach to other lakes and regions requires knowledge of (1) Pb activity, and (3) some understanding of typical sedimentation rates in the study lakes. This approach provides an accurate assessment of OC burial, with increased potential for greater spatial coverage in inland waters and improved ability to address questions focused on terrestrial-aquatic exchanges of organic carbon. LIMNOLOGY and OCEANOGRAPHY: METHODS 210Pb (Rippey and Douglas 2004;Engstrom 2005). Methods that improve our ability to rapidly and accurately estimate OC burial rates over large spatial scales therefore are particularly important to understanding the role inland waters play in the global C-cycle.Here, we present a method that allows for the rapid and accurate assessment of modern (last ~ 10 y) whole-lake OCburial rates using a single sediment sample from the near-center of a lake basin and which accounts for sediment focusing to the sample site. We incorporate the earlier work of Binford and Brenner (1986), who formulated an approach to estimate the trophic state of a lake based similarly on the degree of 210 Pb dilution in the surface sediments. We demonstrate-by validation against conventional measures of whole-lake OC burial-the applicability of this method in a variety of lake types covering a large range of size and depth, and show how this approach furthers our understanding of the transport, focusing, and burial of OC and atmospheric 210 Pb.

Influence of Hydraulic Connectivity on Carbon Burial Efficiency in Mackenzie Delta Lake Sediments

“…The OC flux per area for another LC lake (LD‐1, located in the outer delta, 211 ± 25 gCm −2 year −1 averaged over the core, n = 16, Figure 1) is between the fluxes observed for MD‐2 and UD‐4. All these values are comparable to observations from lakes in the northern USA (9–318 gCm −2 year −1 , Hobbs et al., 2013). Overall, the median carbon flux encountered in lakes around the world is 40 gCm −2 year −1 (not counting reservoirs, see Mendonça et al., 2017) is not really representative of the Mackenzie Delta lakes which show a large range of values.…”

Uniform carbon fluxes in shallow lakes in alternative stable states

“…Sediments were freeze‐dried and analyzed for 210 Pb activity by alpha spectroscopy. We used the method described by Hobbs et al () to estimate C burial rates based on a single sample from each lake. Submersed macrophyte biomass and phytoplankton abundance in the 60 lakes were also sampled annually from 2009 to 2011 with the methods described previously.…”

Organic carbon sequestration in sediments of subtropical Florida lakes

“…OC burial rates at core sites were calculated by multiplying bulk sediment accumulation rates by the proportion of OC in dry sediment. We corrected OC burial estimates from individual core locations for sediment focusing [13] by multiplying the sedimentation rate by the ratio of the expected, regional unsupported 210 Pb inventory (33.5 dpm cm -2 ) [25] to the observed unsupported 210 Pb inventory. This correction was adjusted for cores from Lake Lochloosa, where whole-basin analysis of 13 210 Pb-dated cores indicated that the mean unsupported 210 Pb inventory was lower (21.3 dpm cm -2 ) than the putative regional value.…”

“…Multiple paleolimnological techniques can be used to estimate OC burial in lakes. They range from the rapid, single-core method, to the intensive, whole-basin approach [13]. Recent OC burial estimates are typically derived from analysis of multiple 210 Pb-dated sediment cores [5] and provide information about OC sequestration during the previous ~100 years, sometimes at sub-decadal temporal resolution.…”