Sediment Respiration Pulses in Intermittent Rivers and Ephemeral Streams

Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32-fold to 66-fold upon sediment rewetting. Structural equation modeling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use, and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2 0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting-drying cycles on respiration and CO2 emissions in stream networks. (c)2019. American Geophysical Union. All Rights Reserved.

We thank Y. Etxeberria, L. Sánchez, C. Gutiérrez, G. LeGoff, and B. Launay for laboratory support. D. v. S. was supported by a Short‐Term Scientific Mission of the COST Action CA15113 (SMIRES, Science and Management of Intermittent Rivers and Ephemeral Streams, www.smires.eu ), supported by COST (European Cooperation in Science and Technology) and received additional funding from the EU's 7th Framework Programme for research, technological development, and demonstration under grant agreement 603629 (GLOBAQUA) and a Grant for Research Groups of the Basque University System (IT‐951‐16) funded by the Basque Government. R. M. and B. O. were supported by the Spanish Ministry of Science, Innovation and Universities through project C‐HYDROCHANGE (CGL2017‐86788‐C3‐2‐P and CGL2017‐86788‐C3‐3‐P). F. A. was funded by the Swiss National Science Foundation grants PP00P3_150698 and PP00P3_179089. N. C. was supported by the EU project LIFE+ TRivers (LIFE13 ENV/ES/000341). S. D. L. received funding from the EU's Horizon 2020 research and innovation programme under the Marie Sklodowska‐Curie grant agreement 748625. P. P. and M. P. were supported by INTER‐COST project LTC17017. RF was supported by CONICYT/FONDAT/15130015.