A new look at old carbon in active margin sediments

Drenzek, Nicholas J.; Hughen, Konrad A; Montluçon, Daniel B.; Southon, John; Santos, Guaciara M.; Druffel, Ellen R. M.; Giosan, Liviu; Eglinton, T. I.

doi:10.1130/g25351a.1

Cited by 76 publications

(40 citation statements)

References 46 publications

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“…A number of other studies of the Mackenzie River system (on sediment and suspended OC) have reported similarly low radiocarbon contents ( Figure 6A; Goñi et al, 2005;Drenzek et al, 2007;Hilton et al, 2015;Vonk et al, 2015). This evidence, combined with low carbon preference index values (CPI) for n-alkanes extracted from Mackenzie River sediments (Yunker et al, 2002;Drenzek et al, 2009) suggests that the river carries significant amounts of sedimentary rock-derived "petrogenic" OC as well as pre-aged terrestrial (permafrost) OC that mixes with more modern plant-and minor contributions of algal-derived OC (Goñi et al, 2005;Drenzek et al, 2007;Hilton et al, 2015). The presence of such ancient OC likely at least partially accounts for the old age of the POC we sampled.…”

Section: Sources Of Oc To Suspended and Lower Delta (Lake Ld-1) Lake mentioning

confidence: 89%

Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition

et al. 2016

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Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13 δ C, 14 C) and molecular organic geochemistry (lignin, leaf waxes). High-resolution age models ( 137 Cs, 210 Pb) of downcore lake sediment records (n = 11) along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels). Comparison with earlier published Mackenzie River depth profiles shows that (i) lake sediments reflect the riverine surface suspended load, and (ii) hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale) riverine fluxes and may prove instrumental in shedding light on past behavior of arctic rivers, as well as how they respond to a changing climate.

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Section: Sources Of Oc To Suspended and Lower Delta (Lake Ld-1) Lake mentioning

confidence: 89%

Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition

et al. 2016

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“…Vascular plant material is believed to spend little time sequestered in intermediate reservoirs such as soils, freshwater sediments, and river deltas and contributes minimally to the old 14 C ages often observed on continental shelves. This results in part from the large contribution of petrogenic relative to vascular plant material found in marine sediments (8). All the aforementioned TerrOC materials are important in regulating the global carbon and oxygen cycles.…”

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confidence: 99%

The role of terrestrially derived organic carbon in the coastal ocean: A changing paradigm and the priming effect

Bianchi

2011

Proc. Natl. Acad. Sci. U.S.A.

689

507

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One of the major conundrums in oceanography for the past 20 y has been that, although the total flux of dissolved organic carbon (OC; DOC) discharged annually to the global ocean can account for the turnover time of all oceanic DOC (ca. 4,000–6,000 y), chemical biomarker and stable isotopic data indicate that there is very little terrestrially derived OC (TerrOC) in the global ocean. Similarly, it has been estimated that only 30% of the TerrOC buried in marine sediments is of terrestrial origin in muddy deltaic regions with high sedimentation rates. If vascular plant material—assumed to be highly resistant to decay—makes up much of the DOC and particulate OC of riverine OC (along with soil OC), why do we not see more TerrOC in coastal and oceanic waters and sediments? An explanation for this “missing” TerrOC in the ocean is critical in our understanding of the global carbon cycle. Here, I consider the origin of vascular plants, the major component of TerrOC, and how their appearance affected the overall cycling of OC on land. I also examine the role vascular plant material plays in soil OC, inland aquatic ecosystems, and the ocean, and how our understanding of TerrOC and “priming” processes in these natural systems has gained considerable interests in the terrestrial literature, but has largely been ignored in the aquatic sciences. Finally, I close by postulating that priming is in fact an important process that needs to be incorporated into global carbon models in the context of climate change.

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“…OC in Venice Cut and Nurse Slough, however, is considerably more depleted in 14 C. Bulk OC and < 1.6, 1.6 to 2.0, and 2.0 to 2.5 g cm −3 fractions are similar in radiocarbon isotope values ( 14 C −247 to −114 ‰) but high-density > 2.5 g cm −3 fractions are highly 14 C depleted ( 14 C −339 and −382 ‰, for Venice Cut and Nurse Slough, respectively) and hence the oldest (3300 and 3800 yr BP, respectively). Radiocarbon ages of sediments that are "too old" to reflect deposition of recently-biosynthesized ("young") OC require contributions from old OC (often termed "pre-aged" OC) from terrestrial soil or fossil (rock) OC (Drenzek et al, 2009;Griffith et al, 2010;Blair and Aller, 2012;Douglas et al, 2014;Galy et al, 2015) and/or anthropogenic (petrogenic or fossil fuel combustion) sources (Mitra et al, 2002;Masiello, 2004). Rivers are an important mechanism for redistributing old terrestrial OC (Raymond and Bauer, 2001b;Masiello and Druffel, 2001;Blair and Aller, 2012).…”

Section: Provenance Of Oc In the Sacramento-san Joaquin Deltamentioning

confidence: 99%

The nature of organic carbon in density-fractionated sediments in the Sacramento-San Joaquin River Delta (California)

Wakeham

Canuel

2016

Biogeosciences

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Abstract. Rivers are the primary means by which sediments and carbon are transported from the terrestrial biosphere to the oceans but gaps remain in our understanding of carbon associations from source to sink. Bed sediments from the Sacramento-San Joaquin River Delta (CA) were fractionated according to density and analyzed for sediment mass distribution, elemental (C and N) composition, mineral surface area, and stable carbon and radiocarbon isotope compositions of organic carbon (OC) and fatty acids to evaluate the nature of organic carbon in river sediments. OC was unevenly distributed among density fractions. Mass and OC were in general concentrated in mesodensity (1.6-2.0 and 2.0-2.5 g cm −3 ) fractions, comprising 84.0 ± 1.3 % of total sediment mass and 80.8 ± 13.3 % of total OC (TOC). Low-density (< 1.6 g cm −3 ) material, although rich in OC (34.0 ± 2.0 % OC) due to woody debris, constituted only 17.3 ± 12.8 % of TOC. High-density (> 2.5 g cm −3 ) organicpoor, mineral-rich material made-up 13.7 ± 1.4 % of sediment mass and 2.0 ± 0.9 % of TOC. Stable carbon isotope compositions of sedimentary OC were relatively uniform across bulk and density fractions (δ 13 C −27.4 ± 0.5 ‰). Radiocarbon content varied from 14 C values of −382 (radiocarbon age 3800 yr BP) to +94 ‰ (modern) indicating a mix of young and old OC. Fatty acids were used to further constrain the origins of sedimentary OC. Short-chain n-C 14 -n-C 18 fatty acids of algal origin were depleted in 13 C (δ 13 C −37.5 to −35.2 ‰) but were enriched in 14 C ( 14 C > 0) compared to long-chain n-C 24 -n-C 28 acids of vascular plant origins with higher δ 13 C (−33.0 to −31.0 ‰) but variable 14 C values (−180 and 61 ‰). These data demonstrate the potentially complex source and age distributions found within river sediments and provide insights about sediment and organic matter supply to the Delta.

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A new look at old carbon in active margin sediments

Cited by 76 publications

References 46 publications

Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition

Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition

The role of terrestrially derived organic carbon in the coastal ocean: A changing paradigm and the priming effect

The nature of organic carbon in density-fractionated sediments in the Sacramento-San Joaquin River Delta (California)

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