scholarly journals Carbon content, carbon fixation yield and dissolved organic carbon release from diverse marine nitrifiers

2022 ◽  
Author(s):  
Barbara Bayer ◽  
Kelsey McBeain ◽  
Craig A Carlson ◽  
Alyson E Santoro
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Global Carbon Cycle ◽  
Natural Seawater ◽  
Ammonia Oxidizing Bacteria ◽  
Biogeochemical Models ◽  
Marine Food ◽  
Global Carbon

Nitrifying microorganisms, including ammonia-oxidizing archaea, ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, are the most abundant chemoautotrophs in the ocean and play an important role in the global carbon cycle by fixing dissolved inorganic carbon (DIC) into biomass. The release of organic compounds by these microbes is less well known but may represent an as-yet unaccounted source of dissolved organic carbon (DOC) available to heterotrophic marine food webs. Here, we provide measurements of cellular carbon and nitrogen quotas, DIC fixation yields and DOC release of ten phylogenetically diverse marine nitrifiers grown in multiple culture conditions. All investigated strains released DOC during growth, making up on average 5-15% of the fixed DIC. Neither substrate concentration nor temperature affected the proportion of fixed DIC released as DOC, but release rates varied between closely related species. Our results also indicate previous studies may have underestimated DIC fixation yields of marine nitrite oxidizers due to partial decoupling of nitrite oxidation from CO2 fixation, and due to lower observed yields in artificial compared to natural seawater medium. The results of this study provide values for biogeochemical models of the global carbon cycle, and help to further constrain the implications of nitrification-fueled chemoautotrophy for marine food-web functioning and the biological sequestration of carbon in the ocean.

scholarly journals First pan-Arctic assessment of dissolved organic carbon in lakes of the permafrost region

2021 ◽  
Vol 18 (12) ◽  
pp. 3917-3936
Author(s):  
Lydia Stolpmann ◽  
Caroline Coch ◽  
Anne Morgenstern ◽  
Julia Boike ◽  
Michael Fritz ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Significant Relationship ◽  
Global Carbon Cycle ◽  
Doc Concentration ◽  
Global Carbon ◽  
Permafrost Regions

Abstract. Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in the focus of climate research, but studies so far are limited to specific study regions. In our synthesis, we analyzed 2167 water samples from 1833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between DOC concentrations and the environment. Using published data and unpublished datasets from the author team, we report regional DOC differences linked to latitude, permafrost zones, ecoregions, geology, near-surface soil organic carbon contents, and ground ice classification of each lake region. The lake DOC concentrations in our dataset range from 0 to 1130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding the permafrost regions of our synthesis, we found median lake DOC concentrations of 12.4 mg L−1 (Siberia), 12.3 mg L−1 (Alaska), 10.3 mg L−1 (Greenland), and 4.5 mg L−1 (Canada). Our synthesis shows a significant relationship between lake DOC concentration and lake ecoregion. We found higher lake DOC concentrations at boreal permafrost sites compared to tundra sites. We found significantly higher DOC concentrations in lakes in regions with ice-rich syngenetic permafrost deposits (yedoma) compared to non-yedoma lakes and a weak but significant relationship between soil organic carbon content and lake DOC concentration as well as between ground ice content and lake DOC. Our pan-Arctic dataset shows that the DOC concentration of a lake depends on its environmental properties, especially on permafrost extent and ecoregion, as well as vegetation, which is the most important driver of lake DOC in this study. This new dataset will be fundamental to quantify a pan-Arctic lake DOC pool for estimations of the impact of lake DOC on the global carbon cycle and climate change.

scholarly journals Oceanic efflux of ancient marine dissolved organic carbon in primary marine aerosol

2019 ◽  
Vol 5 (10) ◽  
pp. eaax6535 ◽  
Author(s):  
Steven R. Beaupré ◽  
David J. Kieber ◽  
William C. Keene ◽  
Michael S. Long ◽  
John R. Maben ◽  
...  
Keyword(s):  
Biological Activity ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Global Carbon Cycle ◽  
Breaking Waves ◽  
Sea Surface ◽  
Marine Aerosol ◽  
Global Carbon ◽  
Marine Organic Carbon

Breaking waves produce bubble plumes that burst at the sea surface, injecting primary marine aerosol (PMA) highly enriched with marine organic carbon (OC) into the atmosphere. It is widely assumed that this OC is modern, produced by present-day biological activity, even though nearly all marine OC is thousands of years old, produced by biological activity long ago. We used natural abundance radiocarbon (14C) measurements to show that 19 to 40% of the OC associated with freshly produced PMA was refractory dissolved OC (RDOC). Globally, this process removes 2 to 20 Tg of RDOC from the oceans annually, comparable to other RDOC losses. This process represents a major removal pathway for old OC from the sea, with important implications for oceanic and atmospheric biogeochemistry, the global carbon cycle, and climate.

scholarly journals ABOUT ROLE OF PHOTOSYNTHESIS IN CARBON TURNOVER

2019 ◽  
Vol 47 (4) ◽  
pp. 76-87
Author(s):  
A. A. Ivlev
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Sulfate Reduction ◽  
Subduction Zone ◽  
Global Carbon Cycle ◽  
Carbon Turnover ◽  
Sedimentary Organic Carbon ◽  
Lithospheric Plates ◽  
Global Carbon

The article considers the model of the global carbon cycle, in which photosynthesis is one of the key elements. The model itself is considered as the transition of carbon from the oxidized state to the reduced one and back. This transition is carried out by photosynthesis. The main oxidation of sedimentary organic carbon and its transition to an oxidized form is carried out by means of a natural reaction of thermochemical sulfate reduction, which occurs in the subduction zone (the zone of collision of lithospheric plates). A number of natural facts substantiating some key provisions of the model are given.

scholarly journals Increasing Autochthonous Production in Inland Waters as a Contributor to the Missing Carbon Sink

2021 ◽  
Vol 9 ◽  
Author(s):  
Zaihua Liu ◽  
Hao Yan ◽  
Sibo Zeng
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Carbon Sink ◽  
Global Carbon Cycle ◽  
Inland Waters ◽  
Organic Carbon Burial ◽  
Missing Carbon Sink ◽  
Organic Carbon Storage ◽  
Autochthonous Production ◽  
Global Carbon

Accounting for the residual land sink (or missing carbon sink) has become a major budget focus for global carbon cycle modelers. If we are not able to account for the past and current sources and sinks, we cannot make accurate predictions about future storage of fossil fuel combustion emissions of carbon in the terrestrial biosphere. Here, we show that the autochthonous production (AP) in inland waters appears to have been strengthening in response to changes in climate and land use, as evidenced by decreasing CO2 emissions from and increasing dissolved organic carbon storage and/or organic carbon burial in inland waters during recent decades. The increasing AP may be due chiefly to increasing aquatic photosynthesis caused by global warming and intensifying human activities. We estimate that the missing carbon sink associated with the strengthening AP in inland waters may range from 0.38 to 1.8 Gt C yr-1 with large uncertainties. Our study stresses the potential role that AP may play in the further evolution of the global carbon cycle. Quantitative estimates of future freshwater AP effects on the carbon cycle may also help to guide the action needed to reduce carbon emissions, and increase carbon sinks in terrestrial aquatic ecosystems.

scholarly journals Spatiotemporal Differentiation of Soil Organic Carbon of Grassland and Its Relationship with Soil Physicochemical Properties on the Northern Slope of Qilian Mountains, China

2020 ◽  
Vol 12 (22) ◽  
pp. 9396
Author(s):  
Le Yang ◽  
Wenxiong Jia ◽  
Yang Shi ◽  
Zhiyuan Zhang ◽  
Hui Xiong ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Cycle ◽  
Physicochemical Properties ◽  
Soil Depth ◽  
Global Carbon Cycle ◽  
Qilian Mountains ◽  
Forest Steppe ◽  
Northern Slope ◽  
Global Carbon

The soil organic carbon pool is an important part of the global carbon cycle, and its accumulation and decomposition affect the balance of the global carbon cycle. It is important to understand scientifically the temporal and spatial variation of soil organic carbon (SOC) and its influencing factors, which could aid further understanding of the accumulation and decomposition of SOC. In order to reveal the relationship between soil organic carbon and soil’s physicochemical properties, six plots were selected on the east, middle and west of forest steppes and typical grasslands on the northern slope of Qilian Mountains during two consecutive growing seasons from 2013 to 2014. Soil samples under 0–30 cm were used to study the spatiotemporal differentiation of SOC and its relationship with the soil’s physicochemical properties in the grassland of the study area. The results show that the content of SOC in the grassland in 2013 was higher than that in 2014, and that it decreased gradually from east to west. The content of SOC is significantly different between the soil layer of 0–10 cm and the soil layers of 10–20 cm and 20–30 cm (p < 0.05), and it decreases with increases in soil depth. The SOC content on forest steppe is higher than that on typical grassland. Significant positive correlations appear between SOC with soil water content and soil nutrients (alkaline nitrogen, available phosphorus, available potassium) (p < 0.01), but there are significant negative correlations between SOC and soil temperature, soil pH, and soil electrical conductivity (p < 0.01).

A shifting view of erosion and the carbon cycle

2020 ◽  
Author(s):  
Robert Hilton ◽  
Josh West
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Numerical Models ◽  
Sedimentary Rocks ◽  
Global Carbon Cycle ◽  
Mountain Building ◽  
Organic Carbon Burial ◽  
Mountain Belts ◽  
The Impact ◽  
Global Carbon

&lt;p&gt;Mountain building results in high rates of erosion and the interaction of rocks with the atmosphere, water and life. The resulting geochemical transfers may steer the evolution of the global carbon cycle and Earth&amp;#8217;s long-term climate. For decades, much attention has focused on the weathering of silicate minerals and associated carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) drawdown, and it is now understood that mountains are places where this reaction is most sensitive to changes in climate. However, the focus on silicate weathering belies a multi-faceted role for mountain building and erosion in the carbon cycle. Erosion also mobilises organic carbon from forests, transferring it to rivers and delivering it to long-lived sedimentary deposits, which results in an additional CO&lt;sub&gt;2&lt;/sub&gt; sink. In some mountain belts, exhumation of sedimentary rocks and exposure to the oxygen-rich atmosphere and hydrosphere can release CO&lt;sub&gt;2&lt;/sub&gt; by oxidation of rock organic carbon and sulfide minerals. These fluxes remain poorly constrained.&lt;/p&gt;&lt;p&gt;Here we take stock of our current understanding of all of these processes and the magnitude of their fluxes, focusing on insight from modern-river catchments. We find that the net CO&lt;sub&gt;2&lt;/sub&gt; budget associated with erosion and weathering appears to be controlled by processes that are not widely considered in conceptual or numerical models, specifically the fluxes from organic carbon burial and oxidation, and sulfuric acid weathering reactions. We suggest that lithology plays a major role in moderating the impact of mountain building on the global carbon cycle, with an orogeny dominated by sedimentary-rocks tending towards CO&lt;sub&gt;2&lt;/sub&gt; neutrality, or indeed becoming a CO&lt;sub&gt;2&lt;/sub&gt; source to the atmosphere. Over the coming century, erosion-induced changes in CO&lt;sub&gt;2&lt;/sub&gt; emissions from sedimentary rocks may result in a previously overlooked positive feedback on anthropogenic climate change.&lt;/p&gt;

scholarly journals First Pan-Arctic Assessment of Dissolved Organic Carbon in Permafrost-Region Lakes

2020 ◽  
Author(s):  
Lydia Stolpmann ◽  
Caroline Coch ◽  
Anne Morgenstern ◽  
Julia Boike ◽  
Michael Fritz ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Significant Relationship ◽  
Global Carbon Cycle ◽  
Doc Concentration ◽  
Relationship Of ◽  
Global Carbon ◽  
Permafrost Regions

Abstract. Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in focus of climate research but studies so far are limited to specific study regions. In our synthesis, we analysed 2,167 water samples from 1,833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between DOC concentrations and the environment. Using published data and unpublished datasets from the author team we report regional DOC differences linked to latitude, permafrost zones, ecoregions, geology, near-surface soil organic carbon contents, and ground ice classification of each lake region. The lake DOC concentrations in our dataset range from 0 mg L−1 to 1,130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding the permafrost regions of our synthesis, we found median lake DOC concentrations of 12.4 mg L−1 (Siberia), 12.3 mg L−1 (Alaska), 10.3 mg L−1 (Greenland), and 4.5 mg L−1 (Canada). Our synthesis shows a significant relationship of lake DOC concentration and ecoregion of the lake. We found higher lake DOC concentrations in boreal permafrost sites compared to tundra sites. About 22 % of the lakes in our extensive dataset are located in regions with ice-rich syngenetic permafrost deposits (yedoma). Yedoma contains large amounts of easily erodible organic carbon and we found significantly higher DOC concentrations in yedoma lakes compared to non-yedoma lakes. Compared to previous studies we found a weak significant relationship of soil organic carbon content and lake DOC concentration as well as between ground-ice content and lake DOC. Our pan-Arctic dataset shows that the DOC concentration of a lake strongly depends on its environmental properties, especially on permafrost extent and ecoregion, as well as vegetation, which is the most important driver of lake DOC in this study. This new dataset will be fundamental to quantify a pan-Arctic lake DOC pool for estimations of the impact of lake DOC on the global carbon cycle and climate change.

scholarly journals Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

2017 ◽  
Vol 114 (33) ◽  
pp. 8716-8721 ◽  
Author(s):  
Mark A. Torres ◽  
Nils Moosdorf ◽  
Jens Hartmann ◽  
Jess F. Adkins ◽  
A. Joshua West
Keyword(s):  
Carbon Cycle ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Global Climate ◽  
Sulfide Oxidation ◽  
Global Carbon Cycle ◽  
Hydrochemical Data ◽  
Future Work ◽  
Global Carbon

Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean–atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2. Future work on glaciation–weathering–carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.

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