. CO2 emission from lowland streams of the Pampean región (Argentina).

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

Zagreb

Simposio; 11th Symposium for European Freshwater Sciences; 2019

Croatian association of freshwater ecologists

Quantifying CO2 fluxes between fluvial systems and the atmosphere is necessary to understand the carbon budget at global scale. However, the geographical coverage of CO2 flux data is strongly biased towards North America and Europe. We measured for the first time CO2 concentration and fluxes from 10 streams of the Pampean region (Argentina) characterized by low current velocities and rich macrophyte and biofilm communities. We also analyzed possible drivers of CO2 fluxes, including hydraulics (current velocity and flow), water properties (conductivity, dissolved oxygen, nutrients, alkalinity), and land use (cropland, cattle breeding, natural vegetation, other uses). Mean CO2 concentration in stream water varied between 1255 and 9999 ppm, and all streams were emitters of CO2 to the atmosphere (range: 35-493 mmol/m-2 d-1). However, we observed a high spatial heterogeneity in CO2 fluxes within each stream reach that is possibly associated to differences in current velocity and the presence of macrophytes and algae mats. Our preliminary results show a positive relationship between CO2 flux and cropland cover. Pending further analyses, these results suggest that the CO2 flux may increase with stream metabolic activity, which is enhanced by the higher nutrient load associated to agricultural activities.