Streams and rivers play an important role in the cycle of greenhouse gases and carbon as they transport greenhouse gases, carbon, and nutrients from the soil to larger water bodies and further to the oceans.
They constitute about 85% of the inland water carbon dioxide (CO2) emissions, although they cover less than 20% of the area of freshwater systems. Like lakes, streams are rich in photosynthetic plants and algae, which produce and consume carbon dioxide (CO2) and are therefore important for greenhouse gas fluxes.
Researchers Anne Ojala from the Natural Resources Institute Finland (LUKE) and Jukka Pumpanen from the University of Eastern Finland participated in an international study published in the Nature Geoscience journal that assessed the amount of CO2 fluxes from stream water to the atmosphere. In this study, they observed that current estimates of the role of streams in the carbon cycle are underestimated because the findings are based primarily on daytime measurements, although in reality there are diurnal variations in both CO2 concentrations and fluxes due to the circadian rhythm of temperature and light. Estimates to date are mainly based on discontinuous sampling and discrete measurements where night-time is poorly represented. New automated measurement techniques enable continuous measurements that were utilized in this study.
Time series from continuous CO2 measurements from 66 streams around the world (a total of 57 years of continuous measurement data) stored in the GLObal River CHemistry database (GLORICH) were used in the study. The researchers showed that by taking into account the diurnal changes in CO2 emissions the estimated CO2 emissions from streams were about 200-550 million tons of carbon (0.20-0.55 Pg C) more per year, which is a significant proportion of previous estimates of 650-1800 million tons (0.65-1.8 Pg C) of carbon per year. The results of the study will have a significant impact on global carbon balance calculations and increase the importance of streams in the carbon cycle.
Information about the article:
Gómez-Gener, L., Rocher-Ros, G., Battin, T. et al. Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions. Nat. Geosci. (2021). https://doi.org/10.1038/s41561-021-00722-3
Contact information:
Anne Ojala, Luonnonvarakeskus, tel. +358 50 532 7662, anne.ojala (a) luke.fi
Jukka Pumpanen, Itä-Suomen yliopisto, tel. +358 50 448 6127, jukka.pumpanen (a) uef.fi)
