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Phytoplankton blooms have become a global concern due to the increasing prevalence of eutrophication. Blooms can have societal, environmental, and economic costs that are often associated with decreased recreational value, toxin production, and water treatment, for example. The dependence of phytoplankton dynamics on phosphorus and light inputs is modeled via a stoichiometric approach. The dynamics occur in distinct phases that allow us to make use of multiple timescale analysis to uncover the transient dynamics. As a result, we approximate the length of time a bloom persists and offer geometric and biological interpretations of the transient dynamics. We then couple the ecological phytoplankton model to a socio-economic model governing anthropogenic nutrient inputs. We assume that the human population is made up of cooperators and defectors and that each strategy has an associated cost dependent on social ostracism and social norms, concern for CB, and effort. We find that the human population at a single lake exhibits the hysteresis phenomena. Further, in considering a network of socially connected lakes a third intermediate stable equilibrium appears adding management complexities to achieving favorable outcomes. In both cases we discuss how social ostracism and social pressure are driving factors in causing regime shifts.

Seminar hosted in remote format. Email organizer for Zoom link.