Reservoirs are lake-like habitats created by humans and embedded within a stream network. Organisms that are typical of lakes, like zooplankton, grow in reservoirs but are eventually swept downstream. The addition of zooplankton to streams alters the community composition by provisioning the habitat with easily captured and assimilated prey. Zooplankton are a resource subsidy to streams from reservoirs. We are studying the environmental, ecological and spatiotemporal factors governing the density, composition, and biomass of zooplankton subsidies.