| Summary: | The goal of this study was to address the top-down and bottom-up controls on different microbial web components (bacterioplankton, picophytoplankton, and >3 μm phytoplankton) in an Antarctic lake. Two experiments using a size fractionation approach and nutrient addition were conducted at microcosm scale (2.5 l). The variation in net growth rates (k') of bacterioplankton and phytoplankton size fractions was analyzed after 5 days. The results determined significant differences; whereas bacterioplankton and large phytoplankton showed an increase in their k' when their predators were removed, the picophytoplankton showed a decrease. All the studied plankton components presented the highest k' when nutrients were added. It is suggested that, in this lake, both the top-down and bottom-up regulations account for the regulation of bacterioplankton and large phytoplankton. As for picophytoplankton, the bottom-up control was evident and grazing did not pose a negative impact and rather, had a positive effect probably due to liberation of nutrients. © 2008 Springer-Verlag. Fil:Allende, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
|
|---|