DISSOLVED ORGANIC CARBON IN TWO BRAZILIAN COASTAL LAGOONS: SOURCES AND UTILIZATION FOR HETEROTROPHIC BACTERIA

Abstract

Weevaluated the bacterial utilization of dissolved organic matter (DOM) of a leachate from emergent macrophyte, Typha dontingensis Pers, dominant in two coastal lagoons of different dissolved organic carbon (DOC) concentrations. in the north of Rio de Janeiro State, Brazil. The leachate was added to microcosms with pelagic water from the two lagoons and inoculated with natural bacteria. Control experiments were performed using only pelagic filtered water added to inocculum. Bacterial production, density and biomass were measured every 24 hours, during five days. Bacterial production and biomass were significantly higher in experiments with leachate addition, in both lagoons, in comparison to the controls. Those results indicate that DOM from the macrophyte has a positive influence on bacterial growth. Normalized results also indicate it is not a matter of quantity, but the quality of DOM is better utilized than the DOM from pelagic region.