Rainfall leads to increased &amp;lt;i&amp;gt;p&amp;lt;/i&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in Brazilian coastal lakes

H Marotta,C M Duarte,L Pinho,A Enrich-Prast

doi:10.5194/bg-7-1607-2010

Abstract

Abstract. The variation of partial pressure of CO2 (pCO2), pH, salinity and dissolved organic carbon (DOC) in surface waters of 12 coastal Brazilian lakes was examined following periods of contrasting rainfall. Periods of high rainfall were 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 highly enhanced, on average, from 28.5 ± 6.0 mmol C m−2 d−1 in dry periods to 245.3.1 ± 51.5 mmol C m−2 d−1 following periods of heavy rainfall. The increased inputs of pCO2 following periods of high rainfall are believed to be derived from increased inputs of pCO2 from groundwaters to the lakes.

Highlights

Inland aquatic ecosystems occupy a small fraction of the continents (2 to 4%; Downing et al, 2006), these ecosystems can affect regional carbon balances, as they tend to support higher net carbon fluxes per unit area than those in surrounding terrestrial ecosystems (Cole et al, 2007; Tranvik et al, 2009)
Allochthonous inputs of CO2 can contribute to maintain the partial pressure of carbon dioxide above equilibrium with the atmosphere in aquatic ecosystems (Raymond and Cole, 2003)
The mean increase in maximum daily values of pressure of CO2 (pCO2) following high weekly-accumulated precipitation was about 6 fold, well above that experienced by minimum daily pCO2 values

Summary

Introduction

Inland aquatic ecosystems occupy a small fraction of the continents (2 to 4%; Downing et al, 2006), these ecosystems can affect regional carbon balances, as they tend to support higher net carbon fluxes per unit area than those in surrounding terrestrial ecosystems (Cole et al, 2007; Tranvik et al, 2009). Terrestrial organic carbon, though relatively refractory (Hopkinson et al, 1998), plays an important role in lakes, where it partially supports aquatic food webs (Pace et al, 2004), metabolism (Cole et al, 2000) and contributes to the prevalent carbon dioxide (CO2) supersaturation of lake waters (Sobek et al, 2005). CO2 enrichment of lake waters may closely follow the precipitation pattern (Rantakari and Kortelainen, 2005), possibly reflecting the associated inputs of surface and groundwater waters containing high concentrations of terrestrial organic and inorganic carbon (cf Cole et al 2007)

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Results

Conclusion