Abstract: Terrestrial dissolved organic carbon (t-DOC) is a constitutive part of lake carbon pool and has a profound impact on pelagic food web. Previous field investigation proposed a high contribution of terrestrial organic carbon to zooplankton carbon with an average of 53%. However, terrestrial organic carbon itself cannot support the somatic growth and reproduction of Zooplankton. How can terrestrial organic carbon incorporate to zooplankton biomass? We assume that terrestrial dissolved organic carbon uptake is through an indirect microbial loop. To test this hypothesis, we conducted a lab observation of microbial dynamics during t-DOC (made from corn straw leachate) decay experiment in dark and Daphnia magna feeding experiments with diets including Scenedesmus, decayed and undecayed corn straw, as well as bacteria, flagellate and ciliate isolated during decay experiment. Our results showed that t-DOC can be transferred to bacteria carbon, flagellate carbon and ciliate carbon subsequently. Diets with Scenedesmus and decayed t-DOC supported the highest growth and reproduction rate of D. magna. Diets with flagellate and ciliate showed the medium support to growth and reproduction of D. magna. Diets with undecayed t-DOC and bacteria showed little support to growth and reproduction of D. magna. The results propose a potential path way for t-DOC to be transferred to zooplankton by a microbial loop. Bacteria, flagellates and ciliates finish this bioconversion together. These findings may help us to further understand the linkage between aquatic ecosystem and terrestrial ecosystem and provide a new perspective in lake management.