Production and Accumulation of Organic Matter The Organic Carbon Cycle

1978 ◽  
pp. 3-13 ◽  
Author(s):  
Bernard P. Tissot ◽  
Dietrich H. Welte
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycle

scholarly journals Potential Production of Carbon Gases and Their Responses to Paleoclimate Conditions: An Example From Xiaolongtan Basin, Southeast Tibetan Plateau

2021 ◽  
Vol 9 ◽  
Author(s):  
Gen Wang ◽  
Yongli Wang ◽  
Zhifu Wei ◽  
Zepeng Sun ◽  
Wei He ◽  
...  
Keyword(s):  
Organic Matter ◽  
Tibetan Plateau ◽  
Low Temperature ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Higher Plants ◽  
The Tibetan Plateau ◽  
Climate Conditions ◽  
Burial Flux ◽  
Carbon Gases

Uplift of the Tibetan Plateau plays a significant and lasting role in the variations of climate conditions and global carbon cycle. However, our knowledge is limited due to the lack of long-sequence records revealing rates of CO2 and CH4 production, hampering our understanding of the relationship between paleoclimatic conditions, carbon cycling and greenhouse gas flux. Here, we present a combination of paleoclimate records and low-temperature thermal simulation results from sediments of the Xiaolongtan Basin at the southeastern margin of the Qinghai-Tibetan Plateau, spanning the late Miocene (14.1 ∼ 11.6 Ma). The n-alkane-derived proxies suggested that the sources of organic matter were obviously different: a mixed source including lower organisms and terrestrial higher plants for the Dongshengqiao Formation from 14.1 to 12.6 Ma, and a predominant contribution from terrestrial higher plants for Xiaolongtan Formation between 12.6 and 11.6 Ma. The paleoclimate was generally warm and humid as reflected by the lipid biomarkers, consistent with previous studies. In addition, the carbon gases (including CO2 and hydrocarbon gases) generated by the low-temperature thermal simulation experiments indicated a production rate of CO2 and CH4 were as high as 88,000 ml/kg rock and 4,000 ml/kg rock, respectively, implying there were certain amounts of carbon gases generated and released into the atmosphere during their shallow burial stage. Besides, the calculated production rate of carbon gases and the estimated burial flux of organic carbon varied in response to the variations of paleoclimate conditions. Based on these observations, we propose that the climate conditions predominantly controlled the formation and accumulation of organic matter, which consequently affected the production of carbon gases and burial flux of organic carbon. The results presented here may provide a significant insight into the carbon cycle in the southeast of the Tibetan Plateau.

scholarly journals Dose-dependent regulation of microbial activity on sinking particles by polyunsaturated aldehydes: Implications for the carbon cycle

2015 ◽  
Vol 112 (19) ◽  
pp. 5909-5914 ◽  
Author(s):  
Bethanie R. Edwards ◽  
Kay D. Bidle ◽  
Benjamin A. S. Van Mooy
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Bacterial Community Composition ◽  
Bioactive Molecules ◽  
Nutrient Regeneration ◽  
Carbon Export ◽  
Sinking Particles ◽  
Polyunsaturated Aldehydes ◽  
Open Question

Diatoms and other phytoplankton play a crucial role in the global carbon cycle, fixing CO2into organic carbon, which may then be exported to depth via sinking particles. The molecular diversity of this organic carbon is vast and many highly bioactive molecules have been identified. Polyunsaturated aldehydes (PUAs) are bioactive on various levels of the marine food web, and yet the potential for these molecules to affect the fate of organic carbon produced by diatoms remains an open question. In this study, the effects of PUAs on the natural microbial assemblages associated with sinking particles were investigated. Sinking particles were collected from 150 m in the water column and exposed to varying concentrations of PUAs in dark incubations over 24 h. PUA doses ranging from 1 to 10 µM stimulated respiration, organic matter hydrolysis, and cell growth by bacteria associated with sinking particles. PUA dosages near 100 µM appeared to be toxic, resulting in decreased bacterial cell abundance and metabolism, as well as pronounced shifts in bacterial community composition. Sinking particles were hot spots for PUA production that contained concentrations within the stimulatory micromolar range in contrast to previously reported picomolar concentrations of these compounds in bulk seawater. This suggests PUAs produced in situ stimulate the remineralization of phytoplankton-derived sinking organic matter, decreasing carbon export efficiency, and shoaling the average depths of nutrient regeneration. Our results are consistent with a “bioactivity hypothesis” for explaining variations in carbon export efficiency in the oceans.

scholarly journals Distribution and origin of organic matter in the Baltic Sea sediments dated with 210Pb and 137Cs

2012 ◽  
Vol 39 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Aleksandra Szczepańska ◽  
Agata Zaborska ◽  
Anna Maciejewska ◽  
Karol Kuliński ◽  
Janusz Pempkowiak
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Baltic Sea ◽  
Sediment Accumulation ◽  
Carbon Accumulation ◽  
Accumulation Rates ◽  
The Baltic Sea ◽  
The Baltic ◽  
Carbon Accumulation Rates

Abstract Organic carbon deposited in marine sediments is an important part of the global carbon cycle. The knowledge concerning the role of shelf seas (including the Baltic Sea) in the carbon cycle has increased substantially, however organic carbon accumulation rates in the Baltic sediments still require clarification. This paper describes methods used for assessing organic carbon and nitrogen accumulation rates in six sediment cores collected in the sediment accumulation areas in the Baltic Sea. Mass sediment accumulation rates were based on 210Pb method validated by 137Cs measurements. The organic carbon accumulation rates ranged from 18 to 75 g·C·m−2·yr−1. The C/N ratios and δ13C were used to access sedimentary organic matter provenance. The C/N ratios in the investigated cores vary in the range from 7.4 to 9.6, while δ13C ranged from −24.4‰ to −26.4‰. Results of the terrestrial organic matter contribution in the sedimentary organic matter were calculated basing on δ13C using the end member approach. Large proportion (41–73%) of the sedimentary organic carbon originates on land. The obtained results indicate the Baltic Sea sediments as an important sink for organic carbon. Substantial fraction of the sedimentary load originates on land.

scholarly journals Burial and origin of permafrost organic carbon in the Arctic nearshore zone

2020 ◽  
Author(s):  
Michael Fritz ◽  
Hendrik Grotheer ◽  
Vera Meyer ◽  
Thorsten Riedel ◽  
Gregor Pfalz ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Coastal Erosion ◽  
Stable Carbon Isotopes ◽  
Carbon Isotopic Composition ◽  
Sediment Traps ◽  
The Arctic ◽  
Nearshore Zone ◽  
Carbon Decomposition

<p>Increasing air and sea surface temperatures at high latitudes lead to accelerated thaw, destabilization, and erosion of perennially frozen soils (i.e., permafrost), which are often rich in organic carbon. Coastal erosion leads to an increased mobilization of organic carbon into the Arctic Ocean that can be converted into greenhouse gases and may therefore contribute to further warming. Carbon decomposition can be limited if organic matter is efficiently deposited on the seafloor, buried in marine sediments and thus removed from the short-term carbon cycle. Basins, canyons and troughs near the coastline can serve as sediment traps and potentially accommodate large quantities of organic carbon along the Arctic coast. Here we use biomarkers (source-specific molecules), stable carbon isotopes (δ<sup>13</sup>C) and radiocarbon (Δ<sup>14</sup>C) to identify the sources of organic carbon in the nearshore zone of the southern Canadian Beaufort Sea. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that 40% of all carbon released by coastal erosion is efficiently trapped and sequestered in the nearshore zone. We conclude that permafrost coastal erosion releases huge amounts of sediment and organic matter into the nearshore zone. Rapid burial removes large quantities of carbon from the carbon cycle in depositional settings.</p>

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

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