Abstract

In this work, the density of bacterioplankton, bacterial biomass and environmental variables were monitored in two seasons (summer and winter), two times each month (spring tide and neap tide sampling), over a 12 h period, comprising a tidal cycle (semidiurnal), from subsurface and bottom waters, in a fixed station in the Estuarine Turbidity Maximum Zone (ETMZ) of Paranagua Bay, Brazil. The data were treated with multivariate analyses methods in order to indentify the key controlling factors of the bacterial community dynamics. The microbial community seemed to be structured by a close relationship with the nutrients concentration, mainly by total phosphorous and nitrate. Regardless of variations throughout the tidal cycles, free-living bacteria had a dominant role on the Paranagua's Bay ETMZ.