COUPLING BACTERIAL ABUNDANCE WITH PRODUCTION IN A POLLUTED TROPICAL COASTAL BAY
Keywords:
syto13, flow cytometry, 3H-leucina incorporation, eutrophication, Guanabara Bay,Abstract
Little is known about fluctuation in heterotrophic planktonic bacteria in tropical waters on time-scales of months-to-years. In this study, bacterial abundance, metabolic activity, and chemical parameters were measured weekly at two strategic sites in Guanabara Bay (Brazil, from July 1998 to September 1999. The sites represent the best (eutrophic) and the worst (hypertrophic) water quality scenarios in this bay, A tight coupling between bacterial abundance (9.44 105 cell mL-¹) and bacterial production (1.95 ?gC L-¹ h-¹) was observed at the eutrophic site, where bottom-up processes control bacterioplankton populations. The increment in bacterial abundance was due to active cells, and bacteria were found to be correlated to phytoplankton. At the hypertrophic site, bacterial abundance and production were generally one-fold higher. However, they were not correlated, indicating top-down control of bacterial populations. P and N recycling were measured during estuarine mixing, and correlations with bacteria were observed. Differences in water quality between eutrophic and hypertrophic sites, associated with predation, salinity and other inactivation factors, could explain the patterns of bacterial abundance and activity found along the estuary.
