HETEROTROPHIC BACTERIAL RESPIRATION: A RELEVANT MEASUREMENT FOR THE UNDERSTANDING OF PLANKTON METABOLISM

Abstract

The functional significance of both microbial autotrophs and heterotrophs in overall plankton metabolism and aquatic food webs has been the focus of great deal of aquatic ecology for a long time. Planktonic bacteria have been, more recently, recognized as an abundant and important component of the aquatic biota. Bacteria utilize a large fraction of the carbon that flows within aquatic ecosystems. A significant amount of the carbon produced by bacteria moves up to higher trophic levels; thus, bacterial community structure is driven by a top-down control. The realistic linking between energy as dissolved organic carbon from lower to higher trophic levels is influenced by the magnitude of the respiratory processes. Indeed, the intensity of respi­ration rates is an expression of the sinking of carbon in the system. In our point of view, the ecological gap still is: Why and how heterotrophic bacterial respiration rates are, comparatively, so high in terms of energetic balance at plankton level. All efforts at approaching bacterial respi­ration may take into account this theoretical regard. The objective of the present chapter is to bring up the importance of bacterial respiration data and suggest some fruitful approaches to aquatic microbial ecology. Methodological aspects are discussed as well; moreover, we also will show some preliminary data of bacterial respiration in a floodplain Amazonian lake. Our data suggests that Amazonian aquatic ecosystems are potentially sources of CO, to the atmosphere.