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Carbon gas fluxes from a brown‐water and a clear‐water lake in the boreal zone during a summer with extreme rain events
Author(s) -
Ojala Anne,
Bellido Jessica López,
Tulonen Tiina,
Kankaala Paula,
Huotari Jussi
Publication year - 2011
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2011.56.1.0061
Subject(s) - environmental science , sink (geography) , flux (metallurgy) , atmospheric sciences , chlorophyll a , atmosphere (unit) , precipitation , phytoplankton , environmental chemistry , seasonality , hydrology (agriculture) , dissolved organic carbon , trophic level , chemistry , ecology , geology , nutrient , biology , biochemistry , physics , cartography , geotechnical engineering , organic chemistry , meteorology , geography , thermodynamics
We studied CO 2 and CH 4 fluxes from two boreal lakes with differing trophic status (chlorophyll a 17.8 vs. 48.7 mg m −2 ) and water color (100 vs. 20 mg Pt L −1 ) throughout an open‐water period when summer precipitation doubled, using both floating chambers and concentration gradients. Fluxes measured in chambers were higher, but irrespective of the method, both lakes were heterotrophic and were annual sources of carbon gases to the atmosphere. However, with the annual CO 2 flux of 6.85 (chambers) or 5.43 mol m −2 (gradients), the humic lake had notably higher emissions than the clear‐water lake, where the fluxes were 3.97 and 3.38 mol m −2 , respectively. The annual CH 4 flux from the clear‐water lake was 28.5 (chambers) or 20.5 mmol m −2 (gradients) and from the humic lake 20.7 or 16.2 mmol m −2 , respectively. There were interlake differences in seasonal patterns, but the most obvious changes in fluxes occurred during or just after the rains. In the humic lake, the resulting peak in CO 2 and CH 4 flux was responsible for 46% and 48% of the annual flux, respectively. Before the rains, the clear‐water lake was a small sink of CO 2 or had near‐zero efflux but afterwards became a source of CO 2 . In the humic lake, biological mineralization explained the majority of the fluxes, whereas in the clear‐water lake the association between the biological processes and fluxes was less pronounced.