Hysteresis of the Sarracenia Purpurea Microecosystem in Northern Vermont 2015-2016

The restoration of plant and animal communities damaged by chronic detrital or nutrient enrichment is a long-standing environmental problem. In a replicated greenhouse experiment with the aquatic microbial community that inhabits the cup-shaped leaves of the carnivorous pitcher plant Sarracenia purpurea, we monitored O2 levels and the concentration of bovine serum album (BSA), an effective molecular substitute for detritus. Low BSA enrichment rates triggered a classic hysteresis response, a substantial lag in the return of O2 levels. At intermediate BSA enrichment rates, O2 levels closely tracked BSA concentrations during both the enrichment and recovery phases. High BSA enrichment rates induced an unusual "anti-clockwise" hysteresis in which O2 levels were higher during the recovery phase than during the enrichment phase. These experiments revealed complex dynamic behavior in response to enrichment rates of a single environmental driver. Our results suggest that the past trajectory of enrichment is critical for understanding how systems will respond to restoration initiatives. Specifically, systems that have been exposed to chronic low levels of enrichment may be the ones that are most resistant to restoration efforts that reduce nutrient or detrital inputs.