An experimental study of nanoflagellate bacterivory Um estudo experimental da bacterivoria por nanoflagelados

Heterotrophic nanoflagellate Pseudobodo tremulans (4.8 to 7.0 µm) and heterotrophic bacteria, isolated from coastal waters in Ubatuba, SP, Brazil, were used in experiments to analyze quantitatively the relationships between bacteria and nanoflagellates. The meaning of these results for the role of heterotrophic nanoflagellates in the Ubatuba coastal ecosystem is discussed.<br>O nanoflagelado heterotrófico de dimensões entre 4,8 e 7,0 µm (Pseudobodo tremulans) e uma bactéria heterotrófica, isolados das águas costeiras de Ubatuba, SP, Brasil, foram utilizados em experimentos com o objetivo de analisar quantitativamente as relações entre bactérias e nanoflagelados. O significado dos resultados obtidos em relação ao papel dos nanoflagelados heterotróficos no ecossistema costeiro de Ubatuba é discutido

Metabolic diversity of heterotrophic bacterioplankton over winter and spring in the coastal Arctic Ocean

8 pages, 6 figuresSummary: Metabolic diversity of heterotrophic bacterioplankton was tracked from early winter through spring with Biolog Ecoplates under the seasonally ice covered arctic shelf in the Canadian Arctic (Franklin Bay, Beaufort Sea). Samples were taken every 6 days from December 2003 to May 2004 at the surface, the halocline where a temperature inversion occurs, and at 200 m, close to the bottom. Despite the low nutrient levels and low chlorophyll a, suggesting oligotrophy in the winter surface waters, the number of substrates used (NSU) was greater than in spring, when chlorophyll a concentrations increased. Denaturing gradient gel electrophorisis analysis also indicated that the winter and spring bacterial communities were phylogenetically distinct, with several new bands appearing in spring. In spring, the bacterial community would have access to the freshly produced organic carbon from the early phytoplankton bloom and the growth of rapidly growing specialist phenotypes would be favoured. In contrast, in winter bacterioplankton consumed more complex organic matter originated during the previous year's phytoplankton production. At the other depths we tested the NSU was similar to that for the winter surface, with no seasonal pattern. Instead, bacterioplankton metabolism seemed to be influenced by resuspension, advection, and sedimentation events that contributed organic matter that enhanced bacterial metabolismFinancial support for this study was provided by grants from the Generalitat de Catalunya (DURSI) 2003ACES00029/ANT), the Spanish Ministerio de Educación y Ciencia (REN2002-11565-E/ANT), and the Natural Sciences and Engineering Research Council of Canada (NSERC) through Project CASES under the overall direction of L. Fortier. M.M.S. had a CSIC-I3P postdoctoral contract funded by the Fondo Social Europeo. Special thanks to W.F. Vincent for provinding the opportunity to join CASES and Marie-Êve Garneau for part of the bacterial counts. We thanks our on board sampling team formed by J.M. Gasol, V.Balagué, M. Bayer, O. Guadayol, D. Vaqué, M. Estrada, L. Alonso-Saéz, J. Felipe and M. Vidal. We sincerely tranks our fellow scientists on board and the officers and crew of the CCGS Amundsen for their collaboration and support. We aso thank Jim Grover and anonymous reveiwer for constructive comments and suggestionsPeer reviewe