CO2 and CH4 concentrations and diffusive fluxes, alongside δ13C-CH4 isotopic signature and limnological variables in Alicura, Piedra del Águila and Ramos Mexía reservoirs and lotic sites on Limay river (Patagonia, Argentina)

The aim of this dataset was to provide the first description of seasonal CO2 and CH4 dynamics based on dissolved concentrations, diffusive fluxes, isotopic signature and estimates of CH4 oxidation in the three main reservoirs on the Limay river in Patagonia: Alicura, Piedra del Águila (PdA) and Ezequiel Ramos Mexía (RM), as well as to compare the magnitude of these fluxes with those reported from other reservoir types around the world. Sampling sites were located on the Limay river upstream and downstream of each reservoir, and within each reservoir, covering a distance of around 260 km from the uppermost site upstream of Alicura reservoir (40.7515° S, 71.1130° W) to the lowermost site downstream of Ramos Mexía reservoir (39.2513° S, 68.7414° W). A site at the confluence of Collón Cura affluent with PdA reservoir and another on Collón Cura river further upstream of its confluence with PdA were also sampled (40.4528° S, 70.6629° W and 40.1197° S, 70.7488° W respectively). Each site was visited once during early summer 2019 (January), early autumn 2021 (April) and late spring 2021 (November). In all sites samples were collected from the sub-surface (first 10 cm). Measured variables at each site included CO2 and CH4 partial pressure (in µatm) and diffusive flux (in mg C m-1 d-1), δ13C-CH4 isotopic signature (in ‰), water temperature (in ° C), geographic coordinates, altitude (m.a.s.l.), barometric pressure (Mb), dissolved oxygen concentration (in mg L-1), dissolved organic carbon concentration (in mg L-1), chlorophyll a concentration (in µg L-1), total nitrogen concentration (in µg L-1), pH and conductivity (in µS cm-1).