Effects of Grazing by Macro- and Microzooplankton on Transformations of Colored Dissolved Oganic Matter

Abstract

Abstract : The Navy wishes to develop predictive models describing transformations of CDOM, an assemblage of molecules defined as those that absorb ultraviolet and visible radiation. Our objective was to understand water-column biological processes hypothesized to affect both the 'background' signature of CDOM as well as spatial and temporal changes in CDOM. We performed a series of laboratory experiments designed to understand CDOM transformations associated with micro- and macrozooplankton grazing on phytoplankton. Our approach was to use highly controlled laboratory experiments involving cultured representatives of grazers and prey, and to characterize the time course of CDOM transformations using spectroscopic and chemical techniques. There emerged no significant difference between experimental and control microcosms with respect to production and concentration of DOC and CDOM. Our series of experiments, therefore, stand in contrast to those reported by Strom et al. (1997), in which grazing by macro- and microzooplankton was shown to significantly increase DOC concentrations.