Metabolism and gaseous exchanges in two coastal lagoons from rio de janeiro with distinct limnological characteristics

Abstract

The global metabolism and exchange of gases with the atmosphere were measured during a diel cycle in two tropical coastal lagoons, using tlie cun'es of carbon dioxide and dissolved oxygen. Heterotrophic metabolism (net CO2 production and net O2 consumption) was observed in a black water lagoon (Comprida), and autotropliic metabolism (net O2 production and net CO2 consumption) in a clear water lagoon (linboassica). These differences were attributed to the limnological characteristics of both ecosystems, especially to dissolved organic carbon and the attenuation coefficient of light, which are much liigher in the first environment. During the diel cycle analyzed there was a net release of carbon dioxide into the atmosphere in the first lagoon and a net uptake by the water in the second one. Thus, the importance of coastal lagoons for the global carbon budget deserves further study.