Potential cycling of organic matter in a eutrophic reservoir (Barra Bonita, SP - Brazil)

PANHOTA, R. S.¹ & BIANCHINI JR.¹ , ² , I.

¹ Graduate in Ecology and Natural Resources, Universidade Federal de São Carlos. Via Washington Luiz, km 235. Caixa Postal 676. 13565-905. São Carlos, SP, Brazil. e-mail: prafasp@iris.ufscar.br

² Universidade Federal de São Carlos, Hydrobiology Department, Bioassays and Mathematical Modeling Laboratory. Rod. Washington Luis, km 235, 13565-905, Caixa Postal 676. São Carlos, SP, Brazil. e-mail: irineu@power.ufscar.br

ABSTRACT: Water samples were collected in the Barra Bonita Reservoir - SP (22º32”34.5’ S and 48º29”26.4’ W) in two distinct periods (February/01 and July/01), filtered and enriched with glucose. After that, the samples were incubated at 20ºC for 60 days, under aerobic and anaerobic conditions. During this period, aliquots were collected from the mineralization flasks to determine the organic carbon concentration (dissolved: DOC and particulate: POC). The global decay coefficient and the coefficients of the three routes admitted by the glucose mineralization model were determined by kinetics fitting. In February (rainy season), the mineralization coefficients were higher (c.a.10 times) than the mineralization coefficients of July (dry season). Considering the metabolism, in these two periods, the anaerobic one showed higher mineralization coefficients (1.6 times higher in February and 2.0 times higher in July), than the aerobic one. On the other hand, the carbon immobilization (POC formation) was higher in the aerobic metabolism, in the two periods.

Key-words: Heterotrophic potential, decay kinetics, dissolved organic carbon (DOC), particulate organic carbon (POC).