Directing the Fall of Darwin’s “Grain in the Balance”: Manipulation of Hydraulic Flushing as a Potential Control of Phytoplankton Dynamics

Foodweb interactions, such as competition for limiting resources, are inherently non-linear. Consequently, they can give rise to chaotic, or undeterminable, population dynamics. Population dynamics are not always undeterminable, however, sometimes they are quite predictable. What conditions cause one behavior to prevail over the other? Here we focus on aquatic environments, specifically plankton ecosystems, and show numerically and experimentally that when the magnitude and periodicity of hydraulic flushing and nutrient loading are large chaotic behavior, as described by chaos theory, is replaced by determinable dynamics. In other words, the system only responded to manipulation in a predictable manor when the disturbance to the system was large. It may be that management efforts aimed at maintaining ecosystem health in aquatic systems, e.g., enhancing biodiversity, controlling eutrophication, preventing harmful algal blooms, etc., may require large-scale, controlled manipulations of flushing periodicity and magnitude.