Hydroecology of river plankton: the role of variability in channel flow

The mechanisms by which entrained planktonic organisms survive in river sys tems, despite an inexorable, unidirectional downstream transport, are revis ited. The importance of channel retentivity to downstream population recrui tment is emphasized. The aggregated dead-zone (ADZ) model is shown to be ad equate to explain downstream recruitment of a growing population. The ADZ b ehaviour is more prevalent in sinuous, low-gradient reaches than in other p arts of the river. Plankton selection and dynamics relate conspicuously to flow at higher discharges but other environmental features are important at low flows. Discharge variability is pivotal to the opportunities for potam oplankton to thrive. Copyright (C) 2000 John Wiley & Sons, Ltd.