Primärproduktion in Permafrost beeinflussten Aquatischen Ökosystemen der Arktis (PROPERAQUA)
Physik, Chemie und Biologie des Meeres
Zusammenfassung der Projektergebnisse
The Arctic is warming four times faster than the rest of the world and permafrost is thawing rapidly as response. Associated changes are variations in the emissions and sinks of climate relevant gases in Arctic rivers which presently are largely uncertain. The project PROPERAQUA was the first in acquiring high spatiotemporal measurements of the concentration dissolved oxygen (O2), carbon dioxide (CO2) and methane (CH4) in Kolyma River and tributaries in Northeast Siberia. Results revealed large variability from the late freshet (June) to summer (August) in 2019, associated primarily to the hydrodynamics of the river. Largest CO2 and CH4 efflux were measured in June at the tributary Ambolikha River, and decrease steadily until the summer. Besides the seasonal trend, diel cycles were identified in the river water properties and pCO2 despite a muted day-to-night light shifts, which hints to an active river metabolism throughout the open water period. The identified microbial communities and dissolved organic matter fingerprints differed from the freshet to summer showing a clear seasonal shift in the water sources and processes. Algal blooms developed under CO2- and nutrient-rich conditions and with unlimited light incidence during the summer low water flow. This was evidenced by the biological O2 production measured from O2/Ar ratios, method introduced for the first time in Arctic River with this project. PROPERAQUA provided the first high-spatial resolution of pCH4 in a long transect of an Arctic River, and evidenced the large spatial heterogeneity and hot spots of large riverine CH4 emissions in the well oxygenated river water. These hot spots of CH4 emissions were associated with lateral terrestrial sources of this gas in areas near the river bank and confluence with tributaries. These results were supported by microbial community analysis and highlighted the relevance of lateral exchanges between land and aquatic ecosystems. With projected increase in precipitation and earlier melt periods in the Arctic, longer open water seasons may allow for longer periods of suitable conditions for the development and settlement of algal blooms. Increasing contributions of permafrost carbon can support this process, which essentially modifies the rates of carbon uptake and emissions in Arctic Rivers.
Projektbezogene Publikationen (Auswahl)
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Effects of Reversal of Water Flow in an Arctic Floodplain River on Fluvial Emissions of CO2 and CH4. Journal of Geophysical Research: Biogeosciences, 127(1).
Castro‐Morales, K.; Canning, A.; Körtzinger, A.; Göckede, M.; Küsel, K.; Overholt, W. A.; Wichard, T.; Redlich, S.; Arzberger, S.; Kolle, O. & Zimov, N.
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Highest methane concentrations in an Arctic river linked to local terrestrial inputs. Biogeosciences, 19(21), 5059-5077.
Castro-Morales, Karel; Canning, Anna; Arzberger, Sophie; Overholt, Will A.; Küsel, Kirsten; Kolle, Olaf; Göckede, Mathias; Zimov, Nikita & Körtzinger, Arne
