Reconstruction of Sedimentary Organic Carbon Accumulation Integrating Sediment Chronology, Deposition Rate and SOC Concentration (Past 5 Years)

Abstract. Even though human-induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in TOC content and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC mineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well recorded in the sedimentary record. Overall, eutrophic lakes have higher TOC burial and accumulation rates, and subsurface peaks in TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes, moreover, have higher rates of total respiration and higher contributions of methanogenesis to total respiration. However, we found strong overlaps in the distributions of respiration reactions involving different electron acceptors in all lakes regardless of lake trophic state. Moreover, even though water column P concentrations have been reduced by ∼ 50 %–90 % since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly, by ∼ 20 % and 25 %, in two of the five lakes. Hereby there is no clear relationship between the magnitude of the P concentration decrease and the change in TOC burial and accumulation rate. Instead, data from one eutrophic lake suggest that artificial ventilation, which has been used to prevent water column anoxia in this lake for 35 years, may help sustain high rates of TOC burial and accumulation in sediments despite water column P concentrations being strongly reduced. Our study provides novel insights into the influence of human activities in lakes and lake watersheds on lake sediments as carbon sinks and habitats for diverse microbial respiration processes.

… in Lake Erie was reconstructed using measurements of V3C of sedimented organic C (S13C,,,) … Similarly, the sediment accumulation rate of NAIP increased rapidly during the 1940s and …

… Based on the 210 Pb chronology of four sediment cores sampled in the Beilun River … lignin biomarkers to reconstruct historical changes in OC storage and accumulation rate over the …

… in lake sediments is important to assessing organic matter sources, for reconstructing past productivity rates, and for … Increases in the accumulation rates of organic matter and its …

… [1] Sediment cores were collected from the East China Sea inner shelf in 2010 to study the … and preservation of organic carbon (OC). The highest sediment mass accumulation rate (0.61 …

… provide information that helps to reconstruct past environmental conditions and to assess … C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror …

… the temporal variations in sediment input to SAMO, using a combination of 14 C and 210 Pb dating. This is the first study on the recent evolution of accumulation rates in the lake, and …

… This study examined the lake sediments of five 200-cm-deep dated depositional cores in … cm, suggesting lake sediments at deep layers stored considerable carbon. TOC burial rate (BR …

… mixing that occurred during sediment deposition. Information … organicmatter compositions of the sediments of lakes from different parts of the world have been important in reconstructing …

Floodplains are important sinks in terms of the sediment and carbon flux in … sediment flux, and on the amount of carbon storage in floodplains. Therefore, the influence of the sedimentary …

… to determine sediment accumulation rates in a wide variety of depositional environments … in the amount of sand-size particles in sediment profiles will cause an apparent decrease in …

… Last but not least, we are very happy to point out that the contributions in this volume on “Soil and Sediment Archives” reflect the able scholarship and skills of many excellent women …

A Holocene alluvial archive of 506 dated units for Great Britain is analysed in terms of … sedimentation styles involved. The database is classified by sedimentation unit (channel sediments…

Stable organic carbon (OC) burial into lacustrine sediments was the important C fixation path for atmospheric C reduction. However, OC retention effect and stability mechanisms in sediments was still unclear at the molecular scale during the burial period. Chronology and OC fractions were measured for the sediments from two freshwater lakes. Three-dimensional fluorescence and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were used to detect the change in the forms and molecular structure of soluble OC (SOC). Remarkably increasing TOC and total nitrogen (TN) concentrations along with the decreasing TOC/TN (C/N) values upwards occurred in the sediment columns indicated the weakened terrigenous OC and N inputs from about the 1980s. The OC mineralization contributed to the decrease of C burial in deeper sedimentary layers. However, higher SOC concentrations was found in deeper depths, suggesting that SOC facilitated the OC accumulation and fixation in the sediments and triggered the higher OCBR values over time. Additionally, obvious fluorescence intensity existence throughout the the whole sediment cores suggested the synchronous accumulation of both humic acid-like and fulvic acid-like materials over time as dominant SOC fractions. Higher fluorescence intensity at upper sediment layers indicated the SOC burial as humic acid-like materials with stronger sequestration potential. The persistence of fluorescence signal suggested that fulvic acid-like materials dominated the SOC immobilization and resistance to mineralization in the sediments. Finally, FT-ICR-MS analysis showed that remarkable accumulation of lipids with abundances from 31 to 44 % of organics was attributed to the decomposition of lignins and dominated CHO and CHON formulas and OC compounds. Lipids and lignins with higher abundances dominated the SOC burial and fixation over time even though mineralization occurred. Our work testified that lipids and lignins contributed to the majority of humic acid-like materials and subsequent OC retention in the lacustrine sediments at the geological time scale.

… accumulation characteristics and evolutionary mechanisms of sedimentary organic carbon (SOC) … long-term dynamics of SOC density using multi-proxy analyses of sediment cores from …

… 548) in order to trace the historical variation of nutrient accumulation. … sedimentation rates and sediment accumulation rates. Ranges of dry mass accumulation rates and sedimentation …

… with the ratio of pollen concentration to concentration of sediment. The method assumes … environmental history-if sediment deposition is uniform. When it is not uniform, concentrations …

… Sedimentary C, N, and P concentrations increased with time and were related to land clearing, water impoundment, and agriculture practices, such as fertilization. C:N:P ratios and …

… sediments were measured in order to assess the relative importance of inorganic and organic accumulation… must be determined and subtracted from the total concentration of~~ to .give …

Clarifying the oyster’s carbon budget of their farming ecosystem defines this industry’s future. Through biodeposition, oyster enhances the vertical flux of organic carbon. However, the cycling of sedimented carbon before being separated from the biosphere remains unclear. Here, we constructed the chronologic profiles of the sediment cores from a typical oyster farm with approximately 50 years of farming history. The profiles corresponded with the farming development, environment, associated biogenic elements, and microbial communities. Our results showed the organic carbon burial flux after the onset of intensive farming increased 2.6-fold, reaching 106 g C·m−2·yr−1. Farming development drove the accumulation of microbial necromass, while the percentage of recalcitrant organic carbon in sediment organic carbon also increased from 42.52% to 60.19%. This study highlights the enhancement of carbon storage in response to the development of oyster farming, contributing to the understanding of the ecosystem-based carbon budget for oyster farming. Oyster farming can enhance organic carbon storage in sediments by increasing sediment organic carbon concentration up to 2.6 times, according to an analysis of 50 years of farming data from a typical oyster farm in Sanggou Bay, China.

Soils and sediments store a tremendous amount of organic carbon (OC), especially in the Arctic, but its long-term degradation rate remains poorly constrained. Most work estimate terrestrial OC loss from short-term incubation experiments spanning hours to years, even though soils and sediments develop over centuries to millennia. We quantify the changes in OC reactivity and composition across a chronosequence of floodplain deposits in discontinuous permafrost along the Koyukuk River, central Alaska. We observe minimal OC loss over ca. 6000 years, in sharp contrast to the cycling of surface biomass, which decays on decadal timescales in these environments. These results demonstrate that high-latitude permafrost floodplains are efficient carbon reservoirs that trap and preserve organic matter in transient sedimentary archives. The fate of these highly efficacious OC stores depends on the future dynamics of river migration, erosion, and sediment transport—as much as on changes to plant productivity in a warmer climate. A study of Arctic river floodplains shows that buried organic carbon undergoes minimal degradation over 6,000 years, identifying these landscapes as important long-term carbon reservoirs in a warming Arctic.

Estimating the long‐term sedimentary carbon sinks of mangroves and other blue carbon ecosystems has rapidly become a focus of coastal research and conservation attention. Sampling coverage, however, remains low, with sediment cores sparsely distributed across a subset of mangrove environmental settings globally. Furthermore, the ecological and geological drivers of variation in these stocks remain incompletely understood. We assessed the limits of mangrove sedimentary carbon storage by sampling sediments in diverse mangrove environments across four geographic areas: the volcanic Galapagos, the arid Baja Peninsula, and the geologically and climatically distinct Caribbean and Pacific coasts of Panama. At 80 sites across these areas, we quantified the organic carbon density, sampled with depth, of entire sediment columns. Depth‐integrated carbon stocks are highly variable, from <17 to >1700 MgCorg ha−1. The positive relationship between sediment carbon density and annual rainfall demonstrated in global studies was not observed across these areas, though some carbon density differences were evident. Variation in sediment depth, ranging from 7 to 427 cm across sites, largely explained variation in carbon stock across the areas studied. These results underscore the importance of using measurements of sediment depth to estimate carbon stock. Long‐term geomorphological processes, such as the build‐up of sediment deposits shaped by coastal dynamics, play a major role in shaping mangrove carbon stocks. Investigating and accounting for these processes will enable more accurate estimation of this variable and valuable carbon pool.

… a baseline for sediment carbon stock and accumulation rates. … to the vertical lithostratigraphic sequence of organic-rich peat … The peat corer was pushed vertically into the marsh platform …

… upstream sediment deposition and … m soil cores along a sediment sequence reflecting 80 years of deposition and river course changes. Our analysis of soil organic carbon (SOC) stocks …

… In general, the high annual vertical sediment accretion resulted in higher TOC accumulations among the sampling sites. The TOC accumulations were higher in the vegetated marshes …

Abstract. The mass of carbon stored as organic matter in terrestrial systems is sufficiently large to play an important role in the global biogeochemical cycling of CO2 and O2. Field measurements of radiocarbon-depleted particulate organic carbon (POC) in rivers suggest that terrestrial organic matter persists in surface environments over millennial (or greater) timescales, but the exact mechanisms behind these long storage times remain poorly understood. To address this knowledge gap, we developed a numerical model for the radiocarbon content of riverine POC that accounts for both the duration of sediment storage in river deposits and the effects of POC cycling. We specifically target rivers because sediment transport influences the maximum amount of time organic matter can persist in the terrestrial realm and river catchment areas are large relative to the spatial scale of variability in biogeochemical processes. Our results show that rivers preferentially erode young deposits, which, at steady state, requires that the oldest river deposits are stored for longer than expected for a well-mixed sedimentary reservoir. This geometric relationship can be described by an exponentially tempered power-law distribution of sediment storage durations, which allows for significant aging of biospheric POC. While OC cycling partially limits the effects of sediment storage, the consistency between our model predictions and a compilation of field data highlights the important role of storage in setting the radiocarbon content of riverine POC. The results of this study imply that the controls on the terrestrial OC cycle are not limited to the factors that affect rates of primary productivity and respiration but also include the dynamics of terrestrial sedimentary systems.

… to the delivery and long-term persistence of substantial SOC … in inventories and biogeochemical models. Recent research … into soil biogeochemical models to more accurately predict …

Terrestrial organic carbon (OC) plays an important role in the carbon cycle, but questions remain regarding the controls and timescale(s) over which atmospheric CO2 remains sequestered as particulate OC (POC). Motivated by observations that terrestrial POC is physically stored within soils and other shallow sedimentary deposits, we examined the role that sediment storage plays in the terrestrial OC cycle. Specifically, we tested the hypothesis that sediment storage impacts the age of terrestrial POC. We focused on the Efri Haukadalsá River catchment in Iceland as it lacks ancient sedimentary bedrock that would otherwise bias radiocarbon‐based determinations of POC storage duration by supplying pre‐aged “petrogenic” POC.

… In a separate analysis of the patterns in long-term accumulation in these same lakes (YT Prairie et al., Modeling the accumulation of sediments in lakes of different shapes, in preparation…

The ability of seagrass meadows to filter nutrients and capture and store CO2 and nutrients in the form of organic carbon (OC) and nitrogen (N) in their sediments may help to mitigate local eutrophication as well as climate change via meadow restoration and protection. This study assesses OC and N sediment stocks (top 50 cm) and sequestration rates within Danish eelgrass meadows. At four locations, eelgrass‐vegetated and nearby unvegetated plots were studied in protected and exposed areas. The average OC and N sediment 50 cm stocks were 2.6 ± 0.3 kg OC m−2 and 0.23 ± 0.01 kg N m−2, including vegetated and unvegetated plots. In general, OC and N stocks did not differ significantly between eelgrass meadows and unvegetated sediments. Lack of accumulation of excess 210Pb suggested sediment erosion or low rates of sediment accumulation at most sites. OC accumulation rates ranged from 6 to 134 g m−2 yr−1 and N from 0.7 to 14 g m−2 yr−1. Generalized additive models showed that ≥ 80% of the variation in sediment OC and N stocks was explained by sediment grain size, organic matter source, and hydrodynamic exposure. Long cores, dated with 210Pb, showed declining OC and N densities toward present time, suggesting long‐term declines in eelgrass OC and N pools. Estimates of potential nation‐wide OC and N accumulation in eelgrass sediments show that they could annually capture up to 0.7% ± 0.5% of CO2 emissions and 6.9% ± 5.2% of the total terrestrial N load.

Abstract Coastal wetlands can serve as a considerable sink for carbon (C) gases. However, the capacity for wetlands to serve as more permanent C and N sinks over the long term is less clear given the time dependence of sediment deposition, organic matter decomposition, and anthropogenic land use change. In this study, we compare the short-term (decadal scale) and long-term (millennial scale) C and N accumulation rates estimated using 137Cs and radiocarbon dating of vibracores collected from a freshwater coastal wetland in the Louisiana Mississippi River deltaic plain (Atchafalaya River delta). The mean short-term (60 yrs) sediment accumulation rate was 1.4 cm/yr while the mean rate of long-term (100–1000 yrs) sediment accumulation was an order of magnitude lower at 0.12 cm/yr. Annual rates of C and N accumulated over the past several thousand years were approximately 10% of that over the past 60 years after correcting for bulk density. These results are similar to other coastal wetlands and suggest that time scale must be considered in determining the relative permanence of C and N storage in coastal wetland soils. This difference is especially important for assessing the role of C cycling in relation to global change models and N cycling related to water quality in accurately quantifying the role of coastal deltaic fresh water wetlands in regulating these biogeochemical cycles.

Abstract Permafrost is a distinct feature of the terrestrial Arctic and is vulnerable to climate warming. Permafrost degrades in different ways, including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features. Pleistocene ice-rich permafrost with syngenetic ice-wedges, termed Yedoma deposits, are widespread in Siberia, Alaska, and Yukon, Canada and may be especially prone to rapid-thaw processes. Freeze-locked organic matter in such deposits can be re-mobilized on short time-scales and contribute to a carbon-cycle climate feedback. Here we synthesize the characteristics and vulnerability of Yedoma deposits by synthesizing studies on the Yedoma origin and the associated organic carbon pool. We suggest that Yedoma deposits accumulated under periglacial weathering, transport, and deposition dynamics in non-glaciated regions during the late Pleistocene until the beginning of late glacial warming. The deposits formed due to a combination of aeolian, colluvial, nival, and alluvial deposition and simultaneous ground ice accumulation. We found up to 130 gigatons organic carbon in Yedoma, parts of which are well-preserved and available for fast decomposition after thaw. Based on incubation experiments, up to 10% of the Yedoma carbon is considered especially decomposable and may be released upon thaw. The substantial amount of ground ice in Yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo-erosion processes. Mobilization of permafrost carbon is expected to increase under future climate warming. Our synthesis results underline the need of accounting for Yedoma carbon stocks in next generation Earth-System-Models for a more complete representation of the permafrost-carbon feedback.

… coupled water-sediment-carbon modeling to improve the … storage zones for sediments and associated organic carbon … the long-term stabilization potential of organic carbon under …

… stock has been lost due to post-depositional gully erosion, likely driven by collapse-induced surface destabilization. Stratigraphic … , stratigraphic data, geomorphological analysis, and …

… more accommodation space for carbon storage. This relationship … We also use thermogravimetric analyses to determine the … The post-depositional loss of labile carbon down the …