Q sub(10) of heterotrophic activity during aerobic decomposition of Utricularia breviscapa and its effect on carbon cycling in a tropical lagoon

In this study the Q sub(10) coefficients of heterotrophic activities were measured during aerobic decomposition of Utricularia breviscapa Wright ex Griseb from Oleo lagoon (21 36' S and 49 47' W), Luiz Antonio, SP. The bioassays were set up with fragments of U. breviscapa and incubated with lagoon water at distinct temperatures (15.3, 20.8, 25.7 and 30.3 C). Periodically for 95 days, the concentrations of dissolved oxygen were determined in the bioassays. The results of the temporal variation of dissolved oxygen were fitted to a first-order kinetic model. The stoichiometric relations were calculated on the basis of these fittings. In general, the results allowed us to conclude: i) the oxygen/carbon stoichiometric relations (O/C) varied in function of temperature and time. The temporal variations of the O/C observed in the decomposition of U. breviscapa, suggest that, in the initial phases of the process, low organic carbon concentrations were enough to generate great demands of oxygen, ii) the oxygen consumption coefficients (k sub(d)) presented low variation in function of increasing temperature, iii) the increment of the temperature induced a higher consumption of oxygen (CO sub(max)) and iv) the simulations indicate that during summer, temperature activates the metabolism of decomposing microbiota.Original Abstract: Neste estudo, foram discutidos os coeficientes Q sub(10) das atividades heterotroficas durante a decomposicao aerobia de Utricularia breviscapa Wright ex Griseb da lagoa do Oleo (21 36' S e 47 49' O), Luiz Antonio, SP. Os bioensaios foram realizados com fragmentos de U. breviscapa e agua da lagoa sendo incubados em diferentes temperaturas (15,3, 20,8, 25,7 e 30,3 C). Periodicamente, por 95 dias, as concentracoes de oxigenio dissolvido foram determinadas nos bioensaios. Os resultados da variacao temporal de oxigenio dissolvido foram ajustados a um modelo cinetico de primeira ordem. As relacoes estequiometricas foram calculadas com base nesses ajustes. De modo geral, os resultados permitiram concluir: i) as relacoes estequiometricas (O/C) variaram em funcao da temperature e do tempo. As variacoes temporais dos coeficientes estequiometricos observadas na decomposicao de U. breviscapa sugerem que, nas fases iniciais do processo, concentracoes baixas de carbono organico sao suficientes para gerar grandes demandas de oxigenio; ii) os coeficientes de consumo de oxigenio (k sub(d)) apresentaram baixa variacao em funcao do incremento da temperatura;