Dynamics and estimates of growth and loss rates of bacterioplankton in a temperate freshwater system.
The growth rate and losses of bacterioplankton in the epilimnion of an oligo-mesotrophic reservoir were simultaneously estimated using three different methods for each process. Bacterial production was determined by means of the tritiated thymidine incorporation method, the dialysis bag method and the dilution method, while bacterial mortality was assessed with the dilution method, the disappearance of thymidine-labeled natural cells and ingestion of fluorescent bacterial tracers by heterotrophic flagellates. The different methods used to estimate bacterial growth rates yielded similar results. On the other hand, the mortality rates obtained with the dilution method were significantly lower than those obtained with the use of thymidine-labeled natural cells. The bacterial ingestion rate by flagellates accounted on average for 39% of total bacterial mortality estimated by the dilution method, but this value fell to 5% when the total mortality was measured by the thymidine-labeling method. Bacterial abundance and production varied in opposite phase to flagellate abundance and the various bacterial mortality rates. All this points to the critical importance of methodological aspects in the elaboration of quantitative models of matter and energy flows over the time through microbial trophic networks in aquatic systems, and highlights the role of bacterioplankton as a source of carbon for higher trophic levels in the studied system.
Jugnia
Louis-B
LB
Laboratoire de Biologie des Protistes, Université Blaise Pascal (Clermont-Ferrand II), UMR CNRS 6023, F-63177 Aubière Cedex, France. louis.jugnia@cnrc-nrc.gc.ca
Sime-Ngando
Télesphore
T
Gilbert
Daniel
D
D000818:Animals; D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism; D001431:Bacteriological Techniques; D005618:Fresh Water / Q000382:microbiology*; D010933:Plankton / Q000254:growth & development* / Q000378:metabolism; D011157:Population Dynamics; D013936:Thymidine / Q000378:metabolism; D014871:Water Microbiology
D013936:Thymidine