Q10 of heterotrophic activity during aerobic decomposition of Utricularia breviscapa and its effect on carbon cycling in a tropical lagoon

Abstract

In this study the Q 10 coefficients of heterotrophic activities were measured during aerobic decomposition of Utricularia breviscapa Wright ex Griseb from Óleo 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 d ) presented low variation in function of increasing temperature, iii) the increment of the temperature induced a higher consumption of oxygen (CO max ) and iv) the simulations indicate that during summer, temperature activates the metabolism of decomposing microbiota.Keywords: Q 10 , stoichiometric coefficient, oxygen uptake, aquatic macrophyte, mathematical model. Q 10 da atividade heterotrófica durante a decomposição aeróbia de Utricularia breviscapa e seu efeito na ciclagem do carbono da lagoa do óleo Resumo Neste estudo, foram discutidos os coeficientes Q 10 das atividades heterotróficas durante a decomposição aeróbia de Utricularia breviscapa Wright ex Griseb da lagoa do Óleo (21° 36' S e 47° 49' O), Luiz Antônio, SP. Os bioensaios foram realizados com fragmentos de U. breviscapa e água da lagoa sendo incubados em diferentes temperaturas (15,3, 20,8, 25,7 e 30,3 °C). Periodicamente, por 95 dias, as concentrações de oxigênio dissolvido foram determinadas nos bioensaios. Os resultados da variação temporal de oxigênio dissolvido foram ajustados a um modelo cinético de primeira ordem. As relações estequiométricas foram calculadas com base nesses ajustes. De modo geral, os resultados permitiram concluir: i) as relações estequiométricas (O/C) variaram em função da temperatura e do tempo. As variações temporais dos coeficientes estequiométricos observadas na decomposição de U. breviscapa sugerem que, nas fases iniciais do processo, concentrações baixas de carbono orgânico são suficientes para gerar grandes demandas de oxigênio; ii) os coeficientes de consumo de oxigênio (k d ) apresentaram baixa variação em função do incremento da temperatura; iii) o incremento da temperatura induziu um maior consumo de oxigênio (CO máx ); e iv) as simulações indicaram que, durante o verão, a temperatura favoreceu o aumento do metabolismo da microbiota decompositora.Palavras-chave: Q 10 , coeficientes estequiométricos, consumo de oxigênio, macrófita aquática, modelo matemático.

Bioavailability of pollutants in bacterial communities of Rodrigo de Freitas Lagoon, Rio de Janeiro, Brazil

“…Temperature is one of the most important environmental parameters that affect the metabolism of organisms. The metabolism of organisms reacts to temperature effects exponentially, reaching a peak (at optimum temperature metabolism) and then experiencing a rapid decline in heterotrophic capacity ( Cunha-Santino and Bianchini Júnior, 2010 ). In the present study the temperature data recorded showed values ranging from between 22.1 °C-24.5 °C and these tended to increase with depth ( Figure 2C ).…”

“…In the case of temperature, correlation analysis showed a significant result for organic bacterial carbon (p = 0.04). According to the literature ( Corseuil and Alvarez, 1996 ; Cunha-Santino and Bianchini Júnior, 2010 ), temperature is one of the main parameters to influence microorganism activity and survival. The same authors suggested that lower temperatures decrease cell wall fluidity and permeability, which controls the nutrient and contaminant transport through the microbial cell.…”