Abstract. The variation of surface partial pressure of CO2 (pCO2), pH, salinity and dissolved organic carbon (DOC) in 12 coastal Brazilian lakes was examined following periods of contrasting rainfall. It was tested the hypothesis of a positive relationship of rainfall and the associated transport of terrestrial carbon with pCO2 in tropical lakes. High rainfall was followed by a large, almost 10 fold increase in pCO2 and a one unit decrease in pH in the lakes, whereas no consistent changes in DOC were observed. CO2 emissions to the atmosphere from the Brazilian coastal lakes studied here were enhanced, on average, almost 10 fold, from 28.5±6.0 mmol m−2 d−1 in drier periods to 245.3.1±51.5 mmol m−2 d−1 following heavy rain. Hence, precipitation and subsequent ventilation of groundwater CO2 in lakes might provide an important conduit to deliver CO2 resulting from soil respiration to the atmosphere.
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