Beyond hydraulic flushing: Deep water mixing takes the harm out of a haptophyte algal bloom

► Conducted in-lake mesocosm experiments with natural plankton communities plagued by Prymnesium parvum where we manipulated hydraulic flushing using deeper waters from the lake. ► P. parvum cell densities were reduced by up to 69% and 53%, and ambient toxicity ameliorated, during pre-bloom and bloom development periods. ► Other phytoplankton taxa and zooplankton benefited from these pulsed flushing events. ► These observations provide the first demonstration that P. parvum bloom initiation may be interrupted, and bloom development may be arrested, through hydraulic manipulations.