Quantifying the CO₂ emissions by inland aquatic ecosystems of different trophic statuses may provide helpful information about the role of eutrophication on greenhouse gas emissions. The present study evaluated the CO₂ emissions in three karstic Mediterranean lakes (Lagunas de Ruidera, Spain). We measured vertical profiles of temperature (T), dissolved oxygen (DO), electrical conductivity, and pH along with dissolved nutrients and CO₂ and CO₂ flux during early morning, noon, and evening in each lake during the summer of 2021 and winter of 2022. Gas extraction was carried out following the headspace technique, and the CO₂ flux was measured using open floating chambers. The results showed a significant seasonal variation in the dissolved CO₂ concentration (C_CO2) and the CO₂ flux (F_CO2), but not along the diel cycle (KW, p > 0.05). The C_CO2 values ranged from 9.5 to 107.8 µmol L⁻¹ averaging 50.3 ± 15.14 µmol L⁻¹ over the dry/warm season and 34.9 ± 7.8 µmol L⁻¹ over the rainy/cold one. CO₂ emissions increased in the dry/warm season (4.2 ± 2.1 g CO₂ m⁻² d⁻¹), independently of eutrophication (KW, p < 0.05). However, the oligotrophic lake Conceja exhibited the highest F_CO2 during the dry/warm season (5.6 ± 1.4 g CO₂ m⁻² d⁻¹), but during the rainy/cold the highest emission was recorded in the mesotrophic lake Colgada (4.5 ± 1.8 g CO₂ m⁻² d⁻¹). Our results indicate that temperate karstic lakes are important sources of CO2 driving climate change, particularly due to their correlation with lakes’ trophic status and their high global warming potential. 

Primary Presenter: Mariana Vargas-Sánchez, Universidad Nacional Autónoma de México (marianavs@icloud.com)

Authors:

Mariana Vargas-Sanchez, Universidad Nacional Autónoma de México  (marianavs@icloud.com)

Salvador Sánchez-Carrillo, Museo Nacional de Ciencias Naturales (CSIC)  (sanchez.carrillo@mncn.csic.es)

Javier Alcocer, Universidad Nacional Autónoma de México  (jalcocer@unam.mx)

Ismael Soria-Reinoso, Universidad Nacional Autónoma de México  (ismafs21@gmail.com)

Andrea Guzmán-Arias, Universidad Nacional Autónoma de México  (andreaguzman0@gmail.com)