Spatial variation of harmful algae and their toxins in flowing-water habitats: A theoretical exploration

Abstract

Flow in riverine reservoirs and impoundments can be strong enough to wash out phytoplankton populations, including harmful algae. However, fringing coves and shoreline features can comprise a hydraulic storage zone that enhances algal persistence. Mathematical models of this situation were constructed to represent populations of toxic flagellates or cyanobacteria, and complementary models represented dynamics of exchange between a single cove and a main lake. Steadystate analyses predict that spatial variation in algal abundance and toxin concentration along the axis of flow in a riverine reservoir is most likely to arise for critical flows just below those causing washout, which can be identified by the Péclet number. Spatial variation in algal abundance and toxin concentration between a single cove and the main lake is predicted to occur when a cove is hydraulically isolated from the main lake, or as a transient phenomenon during strong flow events. This modeling suggests a potential for managing harmful algal blooms through flow manipulations in some instances, or by localized controls of abundance or toxicity in relatively isolated coves. © The Author 2010.