Dynamics of planktonic bacteria and heterotrophic microflagellates in the Parker Estuary, northern Massachusetts

The temporal and spatial abundance and activities of members of the planktonic microbial food web in a salt marsh estuary were analysed over the course of a year. Analysis of the data was focused on the factors that control the density and productivity of the heterotrophic bacteria. Temperature exercises a long-term influence on substrate sources, but short-term control is a function of the interaction of grazing and substrate supply. A model has been developed to give a framework for understanding how the microbial food web may work under steady-state assumptions. The model assumptions and predictions appear to be supported by the field data. Equations were generated for estimating substrate flux through the bacteria and estimating bacterial density as a result of grazing and substrate input. The results give some insights into the question of whether the heterotrophic bacteria function as a link to higher organisms or as an energy sink.