Abiotic processes control carbon dioxide dynamics in temperate karst lakes
Por:
Vargas-Sanchez, M, Alcocer, J, Puche, E, Sanchez-Carrillo, S
Publicada:
22 may 2024
Resumen:
Inland waters are crucial in the carbon cycle, contributing significantly to the global CO 2 fluxes. Carbonate lakes may act as both sources and sinks of CO 2 depending on the interactions between the amount of dissolved inorganic carbon (DIC) inputs, lake metabolisms, and geochemical processes. It is often difficult to distinguish the dominant mechanisms driving CO 2 dynamics and their effects on CO 2 emissions. This study was undertaken in three groundwater -fed carbonate -rich lakes in central Spain (Ruidera Lakes), severely polluted with nitrates from agricultural overfertilization. Diel and seasonal (summer and winter) changes in CO 2 concentration (C CO2 ) DIC, and CO 2 emissions-(F CO2 )-, as well as physical and chemical variables, including primary production and phytoplanktonic chlorophyll - a were measured. In addition, 8 13 C-DIC, 8 13 C-CO 2 in lake waters, and 8 13 C of the sedimentary organic matter were measured seasonally to identify the primary CO 2 sources and processes. While the lakes were consistently C CO2 supersaturated and F CO2 was released to the atmosphere during both seasons, the highest C CO2 and DIC were in summer (0.36-2.26 mu mol L -1 ). Our results support a strong phosphorus limitation for primary production in these lakes, which impinges on CO 2 dynamics. External DIC inputs to the lake waters primarily drive the C CO2 and, therefore, the F CO2 . The 8 13 C-DIC signatures below -12 %o confirmed the primary geogenic influence on DIC. As also suggested by the high values on the calcite saturation index, the Miller -Tans plot revealed that the CO 2 source in the lakes was close to the signature provided by the fractionation of 8 13 C-CO 2 from calcite precipitation. Therefore, the main contribution behind the C CO2 values found in these karst lakes should be attributed to the calcite precipitation process, which is temperature -dependent according to the seasonal change observed in 8 13 C-DIC values. Finally, co -precipitation of phosphate with calcite could partly explain the observed low phytoplankton production in these lakes and the impact on the contribution to increasing greenhouse gas emissions. However, as eutrophication increases and the soluble reactive phosphorus (SRP) content increases, the co -precipitation of phosphate is expected to be progressively inhibited. These thresholds must be assessed to understand how the CO 3 2 - ions drive lake co -precipitation dynamics. Carbonate regions extend over 15% of the Earth's surface but seem essential in the CO 2 dynamics at a global scale.
Filiaciones:
Vargas-Sanchez, M:
Univ Nacl Autonoma Mexico, Grad Program Marine Sci & Limnol, Mexico City, Mexico
Alcocer, J:
Univ Nacl Autonoma Mexico, Trop Limnol Grp, FES Iztacala, Mexico City, Mexico
Puche, E:
Museo Nacl Ciencias Nat MNCN CSIC, Biogeochem & Microbial Ecol Dep, Madrid, Spain
Univ Valencia, Cavanilles Insitute Biodivers & Evolutionary Biol, Paterna, Valencia, Spain
Sanchez-Carrillo, S:
Museo Nacl Ciencias Nat MNCN CSIC, Biogeochem & Microbial Ecol Dep, Madrid, Spain
gold, Green Published
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