Bacterial dynamics in periphyton from different regions of a tropical coastal lagoon

Abstract

Various aspects of bacterial dynamics in periphyton attached to leaf detritus of Typha domingensis Pers were examined in a coastal lagoon in the state of Rio de Janeiro, Brazil. Senescent leaves were submerged in eutrophic and oligotrophic regions of this lagoon and the biovolume, abundance, biomass, secondary production ([ 3 H]leucine - leu - and [ 3 H]-thymidine - Tdr - incorporation), and turnover times of the bacterial community were evaluated after five and 25 days of decomposition. An additional experiment was carried out to lest the effects of PP 4 3- and NH 4 + on Tdr incorporation. Bacterial abundance and biomass per unit of detritus surface increased faster in the eutrophic region, but eutrophic and oligotrophic regions did not differ when data were expressed per unit of biofilm dry weight. Despite higher bacterial abundance and biomass, biofilms of the eutrophic region had lower bacterial production, on a biofilm dry weight, and higher turnover times after 25 days of decomposition. Addition of PO 4 3- and NH 4 + significantly increased Tdr incorporation by periphytic bacteria growing in the oligotrophic region significantly, which suggests that this community is P and N limited in that region.