Abstract
On the basis of a broad compilation of data on pCO(2) in surface waters, we show tropical lakes to be, on average, far more supersaturated and variable in CO2 (geometric mean +/- SE pCO(2) = 1804 +/- 35 mu atm) than temperate lakes (1070 +/- 6 mu atm). There was a significant negative relationship between pCO(2) and latitude, resulting in an average decrease of pCO(2) by 2.8 +/- 0.5% per degree latitude. In addition, we found a general positive relationship between pCO(2) and water temperature across lakes involving an average increase (+/-SE) in 6.7 +/- 0.8% per degrees C. A conservative annual efflux from global lakes to the atmosphere was reestimated to 0.44 Gt C. Our results show tropical lakes maintain large CO2 disequilibria with the atmosphere, playing a disproportionate and variable role in the flux of CO between lakes and the atmosphere, thereby being a significant component of the global C cycle.