Temperature Sensitivity of Freshwater Denitrification and N2O Emission—A Meta‐Analysis. Issue 6 (10th June 2022)

• Record Type: Journal Article
• Authors: Velthuis, Mandy; Veraart, Annelies J.
• Is Part Of: Global biogeochemical cycles. Volume 36:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-10
• Subjects: temperature sensitivity -- denitrification -- N2O emissions -- freshwater ecosystems -- Q10 -- N2O emission factor; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2022GB007339
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Freshwater denitrification removes a considerable amount of nitrogen from inland waters, which are under pressure from eutrophication and warming. However, incomplete denitrification can lead to the formation of N2 O, a potent greenhouse gas, which can amplify climatic warming. Although temperature effects on denitrification are well studied in individual habitats and experiments, global patterns in temperature‐responses of denitrification and N2 O emissions remain to be elucidated. Here, we investigated the temperature sensitivity (Q10) of denitrification and N2 O emissions in freshwater ecosystems worldwide, using a meta‐analytic approach. To this end, Q10 values from in‐situ and temperature manipulation studies were related to environmental nutrient conditions, O2, pH, sediment organic matter (SOM), and geographic location. Temperature sensitivity of denitrification displayed a strong positive correlation with environmental nitrogen concentrations, pH and O2 . Significant correlations with SOM and SOM:N ratios were observed as well, but the direction of the effect differed between in‐situ and temperature manipulation studies. Surprisingly, temperature sensitivity of N2 O emissions did not correlate with pH, SOM, nutrient or O2 conditions. Temperature sensitivity of the ratio between N2 O emission and NO3 − concentration (adapted EF5 values) was 6.6 times higher in Australia and New Zealand compared to other geographic regions. As global temperatures and nitrogen deposition in freshwater ecosystems are expected to increase over the coming decades, our results suggest enhanced future denitrification, which may present a natural way to balance eutrophication. The observed temperature sensitivity of N2 O emission factors, however, may indicate enhanced denitrification‐derived N2 O emissions from freshwater ecosystems in a future warmer world. Key Points: One degree warming enhances denitrification and N2 O emissions 8%–14 %. In‐situ Q10N2O is 2 times lower than temperature manipulation Q10N2O Q10denitrification increases with nitrogen and O2 availability. SOM correlations differ between in‐situ and temperature manipulation studies Adapted Q10EF5 is 6.6 times higher in the Australia and New Zealand region compared to regions on the northern hemisphere