The effect of sedimentation and microbial nitrogen regeneration in a plankton community: a simulation investigation

Abstract

A computer simulation model was developed to investigate nitrogen fluxes associated with microbial interactions in plankton communities. A short time scale was used, appropriate to the build-up and decline of phytoplankton blooms in temperate shelf waters after a mixing or upwelling event. The model depicts a continuum of events, many of which have been observed in coastal, upwelling and oceanic systems, including two phytoplankton peaks corresponding to ‘new production’ and ‘regenerated production’. It predicts that nitrogen loss through sedimentation of phytoplankton and faeces may result in a smaller bloom with a delayed onset and prolonged duration. Microbial regeneration of nitrogen was found to be important in sustaining the middle stages of a phytoplankton bloom, whereas micro- and meso-zooplankton regeneration occurred towards the end of the bloom.