Drivers of CO2 emissions in open-canopy streams (Argentina)

MAITE ARROITA; ADONIS GIORGI; JULIETA ANSELMO; LAURA RIGACCI; CLAUDIA FEIJOÓ; MARÍA LAURA MESSETTA; DANIEL VON SCHILLER

Murcia

Congreso; III Iberoamerican Congress of Limnology 2020, Murcia, España (Online Congress); 2020

Carbon dioxide (CO2) emission from fluvial systemsrepresents a substantial flux in the global carbon cycle.However, variation in fluvial CO2 fluxes as well as itsdrivers are poorly understood. Here, we estimatedCO2 concentration and fluxes in 14 open-canopystreams (Pampean region, Argentina) that cover arange of nutrient levels and agricultural land use in thebasins. We analyzed drivers of CO2 fluxes, includingcurrent velocity, stream nutrient concentration, fluvialmetabolism and land use (cropland, cattle breeding,natural vegetation, and other uses). Mean CO2concentration in the streams was 3050 ppm, and allstreams were net emitters of CO2 to the atmosphere.However, the emissions varied considerably amongstreams. CO2 fluxes were related positively with the gasexchange rate coefficient (K600) and agricultural cover,and negatively with net ecosystem production. We alsoobserved a high spatial heterogeneity in CO2 fluxeswithin each stream reach, which was associated toflow variation and the presence of different macrophytespecies and algae mats. Our results indicate thatCO2 fluxes in open-canopy Pampean streams aredriven by hydraulics and aquatic metabolism.