Spatial and temporal variation of bacterioplankton abundance and biomass in a coastal lagoon (Ria Formosa, SE Portugal)

Water samples were collected at bimonthly intervals (April – October 1988) from three stations located in the Ria Formosa coastal lagoon (SE Portugal). Abundance and biovolume of heterotrophic bacterioplankton ranged between 1.2 – 18 x 106 cells.ml-1 and 0.10 - 0.21 μm3.cell-1, respectively. Lowest values were detected at the station close to the ocean and highest values at the station impacted by a domestic effluent. Total bacterial counts showed slight temporal fluctuations while saprophyte numbers (Colony Forming Units) presented a much stronger variation, with maxima during summer. Biovolume exhibited minimal values during summer. Reasons for different patterns of spatial and temporal variability of the bacterial population are discussed.