Phytoplanktonic exudation, bacterial reassimilation and production for three diel cycles in different trophic conditions
Petit, Muriel; Pekala Alves, Gilberto; Lavandier, Pierre
published: Oct 22, 1999
ArtNo. ESP141014603006, Price: 29.00 €
Three diel studies of algae-bacteria relationships were carried out in three French lakes of different trophic status. Primary production was measured by the 14C incorporation method. Exudation and bacterial uptake rates of organic carbon excreted by phytoplankton were studied by selective filtration. The total photosynthetic production rates were 157, 560 and 831 mgC m-2 d-1 and the excretion rates represented 16.8 %, 3.6 % and 3.5 % of the total production in the oligotrophic, mesotrophic and eutrophic lakes, respectively. In these three systems, 37 %, 52 % and 79 % of the exudates were incorporated by the bacteria with kinetics that differed according to the lake: 90 % and 75 % of the uptake occurred fast (within 4 h) in the oligotrophic and eutrophic lakes, respectively, against only 15 % in the mesotrophic lake. Gross bacterial production, determined from 3H-thymidine incorporation rates, was 0.45, 2.29 and 22.8 mgC m-3 d-1 for the oligotrophic to the eutrophic system, i.e. 10.8, 58.2 and 45.6 mgC m-2 d-1, respectively. The results are examined from biological and methodological points of view.