Large CO₂ disequilibria in tropical lakes

Abstract

[1] 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 CO 2 (geometric mean ± SE pCO 2 = 1804 ± 35 matm) than temperate lakes (1070 ± 6 matm). 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°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 CO 2 disequilibria with the atmosphere, playing a disproportionate and variable role in the flux of CO 2 between lakes and the atmosphere, thereby being a significant component of the global C cycle.

Diurnal sampling reveals significant variation in CO2 emission from a tropical productive lake

“…Also differently from what was found by other studies that covered tropical lakes (e.g. Cole et al, 1994;Marotta et al, 2009), Lake Carioca is a small source of atmospheric carbon in comparison to higher latitude lakes. While CO 2 emissions from Lake Carioca averaged only 0.9 mmolCO 2 .m -2 .d -1 , other studies have recorded CO 2 effluxes of 20.9 mmolCO 2 .m -2 .d -1 from Arctic lakes (Kling et al, 1991), 55.6 mmolCO 2 .m -2 .d -1 from a boreal humic lake (Huotari et al, 2009), and 1200 and 90 mmolCO 2 .m -2 .d -1 from two clear-water temperate lakes (Riera et al, 1999).…”

“…Surface water pCO 2 registered in Lake Carioca is very low in comparison to the mean pCO 2 for tropical lakes available in the published literature (1804 matm, Marotta et al, 2009). Also differently from what was found by other studies that covered tropical lakes (e.g.…”

“…Riera et al, 1999;Tank et al, 2009;Huotari et al, 2009); however, much less is known about CO 2 emissions from tropical lakes (e.g. Richey et al, 2002;Marotta et al, 2009;Kosten et al, 2010;Belger et al, 2011). Knowing precisely how much carbon is delivered to the atmosphere by tropical inland waters and understanding the regulation of this process are crucial steps for better assessment of regional and global carbon budgets.…”

The role played by aquatic macrophytes regarding CO2 balance in a tropical coastal lagoon (Cabiúnas Lagoon, Macaé, RJ)

“…Métodos: O fluxo de CO 2 foi estimado por meio de regressões lineares das concentrações de CO 2 na atmosfera interna de câmaras estáticas, and chemistry, the presence of electron acceptors (redox conditions), pH, electrical conductivity (EC) and factors such as water depth and lake size (e.g., Casper et al, 2003, Stadmark andLeonardson, 2005;Frei et al, 2006;Repo et al, 2007;Loeb et al, 2007;Juutinen et al, 2009). As is observed in tropical lakes, some ecosystems can show CO 2 supersaturation for days or even for years (Marotta et al, 2009).…”

“…Among such aquatic systems, lakes have been extensively considered as great CO 2 sources to the atmosphere. Such recognition emerged from a series of surveys based on carbon dioxide partial pressure (pCO 2 ) over water surfaces, encompassing a large number of systems worldwide (Cole et al 1994;Sobek et al 2005;Marotta et al 2009). The net CO 2 flux from these lake surfaces into the atmosphere depict that the water column in these ecosystems are CO 2 supersaturated.…”