Periodic Reporting for period 1 - TCFLAND2SEA (Thawing Carbon From LAND to SEA: Microbial Degradation of Organic Matter and Response to Thawing Permafrost in the Northeast Siberian Land-Shelf System)
Période du rapport: 2020-03-01 au 2022-02-28
East Siberian Arctic Shelf harbours a huge amount of subsea permafrost and gas hydrates, which are thawing and emitting the greenhouse gases CO2 and CH4 from the sediment to the upper water column and atmosphere under the global warming. The giant sleeping carbon in the Arctic Ocean could have severe climate and even socio-economic consequences. The tiny microorganisms in the environment have an important role in regulating the degradation and emission rate of the greenhouse; however, the microbially-driven mechanisms remain to be elusive. This project TCFLand2Sea aims to improve the understanding of the microbial ecosystem in response to thawing PF and their roles in the biogeochemical carbon cycle in the Arctic. For this project, it aims to address the following objectives as well as the structure of different work packages :
1. To develop the microbial lipid-based metabolic flux analysis model on MATLAB to study the group-specific microbial metabolism in the environment.
2. To investigate microbial mediated-methane oxidation processes in methane seep areas in the outer of Laptev Sea, further improving the understanding of methane emission history in the past centuries.
3. To quantitatively estimate carbon flux through the central metabolic network within microbial community in soil and marine sediment, further testing the hypothesis of microbial metabolic and functioning diversity on carbon utilization modes.
4. To constrain the factors on the mediation of organic matter degradation in different environmental conditions, further improving the understanding of the microbial roles in the biogeochemical C cycle.
5. To disseminate the results of this project on fluxomic techniques on microbially-driven biogeochemistry study and attract more attention to Arctic carbon cycling.
1. To develop the microbial lipid-based metabolic flux analysis model on MATLAB to study the group-specific microbial metabolism in the environment.
2. To investigate microbial mediated-methane oxidation processes in methane seep areas in the outer of Laptev Sea, further improving the understanding of methane emission history in the past centuries.
3. To quantitatively estimate carbon flux through the central metabolic network within microbial community in soil and marine sediment, further testing the hypothesis of microbial metabolic and functioning diversity on carbon utilization modes.
4. To constrain the factors on the mediation of organic matter degradation in different environmental conditions, further improving the understanding of the microbial roles in the biogeochemical C cycle.
5. To disseminate the results of this project on fluxomic techniques on microbially-driven biogeochemistry study and attract more attention to Arctic carbon cycling.
To achieve the above objectives, the participant has split the project into four work packages with each having a six-month period. The structure and relationship among these WPs see Fig. 1. The main tasks included the preparation of expedition for new sample collection, development of new method of metabolic flux analysis, incubation of soil and marine sediment with 13C glucose addition, analysis of microbial lipids and their carbon isotope composition, and dissemination of scientific results as well as the following manuscript writing. The preliminary results show:
1: We developed a new approach of lipid-based metabolic flux analysis model on MATLAB platform, which aims to reveal the metabolic C flux pattern for specific/individual group within the microbial community in environmental settings (Objective 1).
2. The further application on soil samples with this model shows a distinct metabolic pattern for Gram-positive vs Gram-negative bacterial groups. The significance of our approach is to provide an experimental evidence of metabolic diversity within the microbial community, supplementing the information of genome-based metabolism information. (Objective 3, 4).
3. To further probe the effect of environmental conditions on the microbial organic matter utilization, we incubated the marine sediments from the Baltic Sea (low-salinity and methanic condition) and Laptev Sea, Arctic Ocean (high salinity and sulphate reduction) with different 13C glucose isotopomers. The preliminary results show a distinct metabolic way in oceanic sediment and terrestrial soil. In detail, soil microbial community prefers to utilize the pentose phosphate pathway to degrade glucose; whereas sedimentary microbes prefer Embden-Meyerhof-Parnas glycolytic pathway. Moreover, sedimentary redox conditions can affect the microbial metabolism with different fluxes through the metabolic network. Our work provides quantitative evidence on the microbial C utilization way, further regulating the biogeochemical C cycle in terrestrial and oceanic environment from the perspective of microbial intercellular activity. (Objective 3, 4, 5)
4. By using the marine sediment from the methane seep area in the outer of Laptev Sea, microbial lipids (e.g. fatty acids and hopenes) and their carbon isotopic compositions suggest a non-active contemporary anaerobic methane oxidization in the upper 20 cm sediment. However, the presence of hopene over upper 20cm sediment suggests an “ancient” aerobic methane microbial community in water column, further imprinting in the archived marine sediments. This work probably indicates that aerobic microbes in water column have an important role of attenuating the methane from the marine sediment in the Laptev Sea, Arctic Ocean. (Objective 2)
5. This project and the preliminary results have been disseminated via the various ways including social media and scientific conferences. It has been publicized on social media such as Facebook, Twitter, Instagram and departmental website after merging with the International Siberian Shelf Study 2020. The participants presented the results on several conferences including European Geosciences Union General Assembly, Bolin Day and ACES Day in 2021. The dissemination of this project aims to advancing the public attention on the global change in Arctic C cycling. (Objective 5)
1: We developed a new approach of lipid-based metabolic flux analysis model on MATLAB platform, which aims to reveal the metabolic C flux pattern for specific/individual group within the microbial community in environmental settings (Objective 1).
2. The further application on soil samples with this model shows a distinct metabolic pattern for Gram-positive vs Gram-negative bacterial groups. The significance of our approach is to provide an experimental evidence of metabolic diversity within the microbial community, supplementing the information of genome-based metabolism information. (Objective 3, 4).
3. To further probe the effect of environmental conditions on the microbial organic matter utilization, we incubated the marine sediments from the Baltic Sea (low-salinity and methanic condition) and Laptev Sea, Arctic Ocean (high salinity and sulphate reduction) with different 13C glucose isotopomers. The preliminary results show a distinct metabolic way in oceanic sediment and terrestrial soil. In detail, soil microbial community prefers to utilize the pentose phosphate pathway to degrade glucose; whereas sedimentary microbes prefer Embden-Meyerhof-Parnas glycolytic pathway. Moreover, sedimentary redox conditions can affect the microbial metabolism with different fluxes through the metabolic network. Our work provides quantitative evidence on the microbial C utilization way, further regulating the biogeochemical C cycle in terrestrial and oceanic environment from the perspective of microbial intercellular activity. (Objective 3, 4, 5)
4. By using the marine sediment from the methane seep area in the outer of Laptev Sea, microbial lipids (e.g. fatty acids and hopenes) and their carbon isotopic compositions suggest a non-active contemporary anaerobic methane oxidization in the upper 20 cm sediment. However, the presence of hopene over upper 20cm sediment suggests an “ancient” aerobic methane microbial community in water column, further imprinting in the archived marine sediments. This work probably indicates that aerobic microbes in water column have an important role of attenuating the methane from the marine sediment in the Laptev Sea, Arctic Ocean. (Objective 2)
5. This project and the preliminary results have been disseminated via the various ways including social media and scientific conferences. It has been publicized on social media such as Facebook, Twitter, Instagram and departmental website after merging with the International Siberian Shelf Study 2020. The participants presented the results on several conferences including European Geosciences Union General Assembly, Bolin Day and ACES Day in 2021. The dissemination of this project aims to advancing the public attention on the global change in Arctic C cycling. (Objective 5)
Microbes are the main player on the biogeochemistry C cycling. Their activity, functioning and metabolic way will exert an effect on this process. This project emphasizes two important processes relevant to C cycling: microbial organic carbon utilization way and methane oxidation process in marine sediment in the Arctic Ocean. To end this, 1) a novel method of probing microbial metabolic activity on the intercellular scale is developed. It aims to study how microbes utilize the organic matter in the metabolic network, further emphasizing how environmental conditions change the microbial activity and the feedback mechanism of microbes on the biogeochemical C cycling; 2) Methane oxidation processes had been probed in methane seep area in the outer of the Laptev Sea. It will improve the understanding of the methane oxidation process in Arctic, and reduce the uncertainty in the future of methane emission estimate.
Overall, the main results are expected to attract the public and scholars’ attention on tiny and widespread microbes, and address the missing link between microbial mediation on C cycling and climate change in Arctic. It will further improve the public awareness on Arctic change and the summary will be accessible for the climate decision makers (e.g. Sweden, China and European Commission) in the form of oral presentations/consultation.
Overall, the main results are expected to attract the public and scholars’ attention on tiny and widespread microbes, and address the missing link between microbial mediation on C cycling and climate change in Arctic. It will further improve the public awareness on Arctic change and the summary will be accessible for the climate decision makers (e.g. Sweden, China and European Commission) in the form of oral presentations/consultation.