Fig. 2. Integrated model network diagram. We show forcing functions and internal components as circles and boxes, respectively.
Note: Production benefits (Bp) are the economic benefits associated with phosphorus loading and environmental benefits (Be) are the economic benefits associated with environmental quality, measured here by water clarity. The numbers 1, 2, and 3 indicate the three feedback loops within the integrated model. Feedback loop 1 couples the Sandusky Bay ecological model with the phosphorus management model. In this loop, river-soluble reactive phosphorus (SRP) load drives a lower trophic-level model that determines water clarity. This water clarity output determines Be which then determines environmental stakeholder pressure, influencing both management pressure and phosphorus management change. Completing the loop, river SRP load is automatically adjusted to reflect changes in phosphorus management. Feedback loop 2 captures the cycle where changes in phosphorus management alter Bp, determining phosphorus stakeholder pressure and influencing both management pressure and phosphorus management change. Feedback loop 3 exists within the lower trophic level of the ecological model. Phosphorus concentration drives algal dynamics that, in turn, drive zooplankton dynamics. Zooplankton population size determines the quantity of internal phosphorus loading due to excretion, affecting the future phosphorus concentration. Invasive dreissenid mussels impact the social–ecological system by influencing feedback loop 3 (dashed lines).