Periodic Reporting for period 2 - CHROME (Linking Chemical diversity and Reactivity of Arctic dissolved Organic Matter for its integration in Earth system models)
Berichtszeitraum: 2022-03-01 bis 2023-02-28
Dissolved organic matter (DOM) is exported from terrestrial to freshwater ecosystems where, not only is it being degraded and eventually lost as CO2, but such degradation occurs faster than in soils or marine systems. Across freshwaters, variations in DOM degradation and reactivity have been related to compositional changes in DOM. The flux from terrestrial to aquatic systems seems to be increasing associated to anthropogenic perturbations. However, despite the relevance of these fluxes for the global C cycle, Earth System Models (ESMs) are just starting to consider them. In that sense, a particularly crucial region deserving urgent attention is the Arctic, as is suffering exacerbated effects of climate change, holds a massive C stock that is vulnerable to being mobilized towards freshwaters and is th region with the highest density of lakes in the world. Such transfer could turn that vulnerable C stock from a sink into a CO2 source. Therefore, determining the reactivity of that OC flux and incorporating it in surface models is key at the moment. The foundation of CHROME is the idea that the chemical diversity of DOM explains its reactivity and, as such, should be considered in biogeochemical models. CHROME is based on the good match between the previous experience of the applicant and the excellence of the host institutions, leaders in the field of biogeochemical research in Arctic ecosystems (USGS- Boulder, US) and in global modelling (LSCE-CNRS, France). CHROME will constitute a key advance in C biogeochemical understanding and modelling at the forefront of geosciences research.The action responds to three identified needs (1) to advance our biogeochemical understanding of DOM degradation processes, (2) to improve its representation in regional surface system models and (3) to contribute to understand the fate of DOM matter being thawed from Arctic soils.
The main conclusions reached by the project have been:
i) Using molecular-level data of DOM composition obtained through ultra-high resolution mass spectrometry, we identified that chemical diversity indices based on the presence/absence were better predictors of DOM degradation and bacterial respiration parameters than indices based on the expected chemical function of the compounds
ii and iii) On the links between landscape predictors and DOM degradation with the aim of finding key relationships to be implemented in ESM, we can conclude:
a. Rock-weathering impacts DOM and nutrients content and processing in high- Arctic streams, due to the petrogenic origin of those elements. That was specially important in specific geologies, such those dominated by Jurassic sedimentary materials
b. For lakes and ponds in the high-Arctic, isolation (in terms of hydrological connectivity) and distance to the sea are good predictors of DOC concentration and DOM composition at the molecular level and ultimately, of the CO2 and CH4 emissions of those sites.
The main conclusions reached by the project have been:
i) Using molecular-level data of DOM composition obtained through ultra-high resolution mass spectrometry, we identified that chemical diversity indices based on the presence/absence were better predictors of DOM degradation and bacterial respiration parameters than indices based on the expected chemical function of the compounds
ii and iii) On the links between landscape predictors and DOM degradation with the aim of finding key relationships to be implemented in ESM, we can conclude:
a. Rock-weathering impacts DOM and nutrients content and processing in high- Arctic streams, due to the petrogenic origin of those elements. That was specially important in specific geologies, such those dominated by Jurassic sedimentary materials
b. For lakes and ponds in the high-Arctic, isolation (in terms of hydrological connectivity) and distance to the sea are good predictors of DOC concentration and DOM composition at the molecular level and ultimately, of the CO2 and CH4 emissions of those sites.
I integrated in Water Research Area of the United States Geological Service (USGS) in Boulder, Colorado on March 13th 2020. One week after that, the access to the USGS facilities stopped and all the researchers were in lock down and doing online work due to the COVID-19 pandemic. I came back to Europe on November 2020 to continue my MSCA on distance mode. I would like to stress how difficult it was to move to another continent twice during that period and to manage the action with all the administrative agents working from home, which made communications really problematic and the whole action development much more challenging than in regular conditions.
Despite the challenges associated to those changes, samples were analyzed in collaboration with the people in the MagLab in Florida who also provided online guidance on the samples calibration and mass assignment that allowed me to have a full data set ready to be statistically analyzed before leaving the USGS. Moreover, during these months, I took the challenge of developing several papers to push further our understanding on DOM degradation across ecosystems, that crystalized in a couple of perspective/review papers (Kothawala et al. and Xenopoulos et al) . Moving back to the LSCE in France allowed me to supervise the BSc student Apoline Zahorka, which project contributed to the compilation of landscape variables, particularly those regarding the hydrological connectivity of ponds and lakes and compare those with the results obtained by water isotopes. We soon realized that the completely isolated systems were not fitting well the models for water isotopes and that the information obtained through GIS provided a better proxy. Then, we crossed that information with the DOC degradation and DOM composition, finding that isolated ponds in the high-Arctic, act as sinks of CO2, having a DOM of aromatic and coloured character mainly from macrophyte sources. Furthermore, we expanded the span of CHROME by joining an expedition to Zackenberg (eastern Greenland) with researchers from Aarhus University. That expedition allowed us to sample 14 streams in contrasting geological sets to identify the links between organic matter and geology. We found that petrogenic carbon and nitrogen might play a key role on the function of those pristine streams and identified the geologies that might be more influential. Thanks to those activities, through the MSCA CHROME, I have contributed directly or indirectly to the development of 12 peer-reviewed papers, 7 presentations in conferences (2 forthcoming) and 6 invited seminars during these two years. As well as in several outreach activities and actions to achieve gender equity in Geosciences.
Despite the challenges associated to those changes, samples were analyzed in collaboration with the people in the MagLab in Florida who also provided online guidance on the samples calibration and mass assignment that allowed me to have a full data set ready to be statistically analyzed before leaving the USGS. Moreover, during these months, I took the challenge of developing several papers to push further our understanding on DOM degradation across ecosystems, that crystalized in a couple of perspective/review papers (Kothawala et al. and Xenopoulos et al) . Moving back to the LSCE in France allowed me to supervise the BSc student Apoline Zahorka, which project contributed to the compilation of landscape variables, particularly those regarding the hydrological connectivity of ponds and lakes and compare those with the results obtained by water isotopes. We soon realized that the completely isolated systems were not fitting well the models for water isotopes and that the information obtained through GIS provided a better proxy. Then, we crossed that information with the DOC degradation and DOM composition, finding that isolated ponds in the high-Arctic, act as sinks of CO2, having a DOM of aromatic and coloured character mainly from macrophyte sources. Furthermore, we expanded the span of CHROME by joining an expedition to Zackenberg (eastern Greenland) with researchers from Aarhus University. That expedition allowed us to sample 14 streams in contrasting geological sets to identify the links between organic matter and geology. We found that petrogenic carbon and nitrogen might play a key role on the function of those pristine streams and identified the geologies that might be more influential. Thanks to those activities, through the MSCA CHROME, I have contributed directly or indirectly to the development of 12 peer-reviewed papers, 7 presentations in conferences (2 forthcoming) and 6 invited seminars during these two years. As well as in several outreach activities and actions to achieve gender equity in Geosciences.
CHROME has allowed us to develop two statistical models linked to the two main datasets, linking landscape predictors to DOM chemical diversity and reactivity. Thus, we are able to obtain a spatial explicit distribution of DOM degradability in Arctic freshwaters through GIS based statistical modelling.
The project has been communicated in different audiences: scientific, in scientific conferences, organizing special sessions and in invited seminars as well as to the general public in social media, blogs, conferences for school and high school students between 8 and 18 years old, Wikipedia articles contribution, etc. Moreover, I participated in the review of the ARII of the last IPCC report during December 2020. Additionally, CHROME results are aligned with The EU STRATEGY OF ADAPTATION TO CLIMATE CHANGE. We address a major climate feedback, climate feedbacks affecting Arctic ecosystems, which magnitude is a major uncertainty in climate change science. Additionally, this project will contribute to the EU's preparedness for current and future climate impacts, including the European Green Deal. It is also in line with the UN FRAMEWORK CONVENTION ON CLIMATE CHANGE (UNFCC), particularly on the preparation of reports for the Intergovernmental Panel on Climate Change (IPCC) and with the UN SUSTAINABLE DEVELOPMENT GOALS, especially SDG 6 (clean water) and SDG 13 (climate action).
The project has been communicated in different audiences: scientific, in scientific conferences, organizing special sessions and in invited seminars as well as to the general public in social media, blogs, conferences for school and high school students between 8 and 18 years old, Wikipedia articles contribution, etc. Moreover, I participated in the review of the ARII of the last IPCC report during December 2020. Additionally, CHROME results are aligned with The EU STRATEGY OF ADAPTATION TO CLIMATE CHANGE. We address a major climate feedback, climate feedbacks affecting Arctic ecosystems, which magnitude is a major uncertainty in climate change science. Additionally, this project will contribute to the EU's preparedness for current and future climate impacts, including the European Green Deal. It is also in line with the UN FRAMEWORK CONVENTION ON CLIMATE CHANGE (UNFCC), particularly on the preparation of reports for the Intergovernmental Panel on Climate Change (IPCC) and with the UN SUSTAINABLE DEVELOPMENT GOALS, especially SDG 6 (clean water) and SDG 13 (climate action).