Changes in environmental conditions can lead to a rapid shift in the state of an ecosystem ("regime shift"), which subsequently returns to the previous state slowly, if ever ("hysteresis"). Studies of ecological regime shifts have been hampered by the large spatial and temporal scales over which they occur and the lack of a common framework linking observational and experimental data to models. The naturally-occurring aquatic micro-ecosystem inside leaves of the northern pitcher plant (Sarracenia purpurea) occurs in both oligotrophic and eutrophic states. These alternative states also can be induced experimentally by enriching oligotrophic pitchers with additional insect prey, which elevates oxygen demand by microbes and leads to rapid eutrophication. This regime shift of the Sarracenia micro-ecosystem has been modeled with discrete-time difference equations that include parameters for the photosynthetic rate of the pitcher plant, consequent diffusion of oxygen through the pitcher liquid, rate of prey input, and biological oxygen demand by microbes as they decompose and mineralize the prey. We elaborated the regime-shift model of the Sarracenia micro-ecosystem and used sensitivity analysis to identify the parameters that control most strongly the dynamics of the system as it switches between oligotrophic and eutrophic states. Three main findings emerged. 1) Simulations accurately captured the regime shift and subsequent hysteresis that follows from prey enrichment; 2) When modeled as a modified Hill function, the interaction of prey input and decomposition rates drove the regime shift; 3) The interaction between biological oxygen demand of the food web and decomposition rate yielded a threshold that altered the hysteresis dynamics, shifting the sign of the effect of increasing the oxygen demand parameter. Because the model of the Sarracenia micro-ecosystem displays behaviors that are qualitatively similar to larger scale models of dynamic systems, we suggest that the Sarracenia micro-ecosystem itself represents a valuable and scalable experimental system for studying ecological regime shifts.