Freshwater inflows to estuaries have been greatly reduced in many regulated coastal catchments. In this talk we will outline the important role that freshwater inflows have in carbon cycling and estuarine food webs in South-East Australian catchments. The majority of organic carbon is delivered to estuaries during episodic floods and freshes. During these periods the bioavailability of dissolved organic carbon (DOC) doubles resulting in significant increases in bacterial growth and production. We carried out a mesocosm experiment on the Bega River estuary to examine whether DOC and the microbial loop could act as a link to zooplankton production. We added DOC leachate to 400 L mesocosm bags mimicking differently sized inflow events at concentrations of +1.5, +3 and +16mg C L^-1 additions. DOC additions led to significant increases in bacterial production in all treatments. Between days 5-9 of the experiment calanoid copepodites of Sulcanus conflictus and Gladioferens pectinatus were significantly higher in abundance in the +16mg C treatment. Between days 9-15 adults of both species were significantly higher in both the +3 and +16mg C treatment. Stable isotope results indicate increased abundance was supported by DOC leachate. These results, in conjunction with longer term monitoring results on the estuary, provide strong evidence that inflow derived organic carbon plays an important role as a resource subsidy to estuarine zooplankton. Environmental flow rules for estuaries will therefore be important for protecting and maintaining these ecological processes.