Aquatic Sciences Meeting, Albuquerque 2001

CS20 Microbial Dynamics

Date: Friday, February 16, 2001, Time: 10:15:00 AM

Location: Ruidoso/Pecos

Cauchie, H, M, CRP-Gabriel Lippman, CREBS, , Luxembourg, cauchie@crpgl.lu

Jacquet, V, , CRP-Gabriel Lippman, CREBS, , Luxembourg, jacquet@crpgl.lu

Hoffman, L, , Universite de Liege, Institut de Botanique, Liege, Belgium, lhoffman@ulg.ac.be

SEASONAL DYNAMICS OF METABOLICALLY ACTIVE BACTERIOPLANKTON IN A MESO-EUTROPHIC RESERVOIR

The dynamics of the major components of the microbial loop (bacteria and protists) were followed in a dimictic, meso-eutrophic reservoir. In the epilimnion and metalimnion, the “total” bacterioplankton density, determined using Acridine Orange (AO) staining, varied between 800.000 (in autumn and winter) and 4.000.000 (in spring and summer) “cells” per ml. The active fraction, estimated using CTC reduction as an indicator of respiratory metabolism, ranged between 10-20 % (in spring and summer) and 40-60 % (in autumn and winter) of AO counts. The results suggest a negative relationship between the activity of bacterioplankton and the development of bacterivores. In the hypolimnion, the active fraction showed no clear seasonal variations, oscillating between 5 and 30 % of AO counts. Furthermore, the adequacy of using CTC reduction as a measure of the metabolically active fraction was tested by comparing the results, during several key-periods, with those determined by a vital stain (propidium iodide). The coherence of per cell production values obtained on the basis of metabolically active biomass estimates was also checked.

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Aquatic Sciences Meeting, Albuquerque 2001

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