Abstract
Evidence shows the important role biota play in the carbon cycle, and strategic management of plant and animal populations could enhance CO2 uptake in aquatic ecosystems. However, it is currently unknown how management-driven changes to community structure may interact with climate warming and other anthropogenic perturbations to alter CO2 fluxes. Here we showed that under ambient water temperatures, predators (three-spined stickleback) and nutrient enrichment synergistically increased primary producer biomass, resulting in increased CO2 uptake by mesocosms in early dawn. However, a 3°C increase in water temperatures counteracted positive effects of predators and nutrients, leading to reduced primary producer biomass and a switch from CO2 influx to efflux. This confounding effect of temperature demonstrates that climate scenarios must be accounted for when undertaking ecosystem management actions to increase biosequestration.