Ref ID : 3954
Christian Amblard, Telesphore Sime-Ngando, Saad Rachiq, and Gilles Bourdier; Importance of ciliated protozoa in relation to the bacterial and phytoplanktonic biomass in an oligo-mesotrophic lake, during the spring diatom bloom. Aquat.Sci. 55/1:1-9, 1993
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The abundance and the biomass of bacterial, phytoplanktonic, and ciliate communities were estimated at different depths during the spring planktonic development in an oligo-mesotrophic lake (the Pavin lake). The bacterial population, which consists mainly of free bacteria (94% of the total bacterial abundance), displays only low cell densities (0.6 to 7x10E5 cells/ml) and represents low biomass values (0.9 to 11.5 µgC/l). The bacteria represent from 0.9 to 23.8% (M=9.7%) of the "microplanktonic biomass" (with the exclusion of heterotrophic nanoflagellates, i.e. bacteria + phytoplankton + ciliates, size range 0.2-160 µm). The abundance of the phytoplankton varies between 0.5 and 1.8x10E6 cells/l, and the biomass values between 12 and 118 µgC/l. The phytoplankton population constitutes the largest part of the microplanktonic biomass (51.9 to 96.6%, M=80.6%), and the diatom Melosira italica subsp. subarctica is the largely dominant species of this community. The population of ciliates, essentially Oligotrichida and Scuticociliatida, displays densities between 1.3 and 38.3x10E3 cells/l (M=6.7x10E3 cells/l), and biomass values vary from 0.10 to 16.30 µgC/l (M=6.01 µgC/l). The ciliates constitute thus from 0.1 to 26.4% (M=9.8%) of the microplanktonic biomass. Whereas the oligotrichs are best represented in the euphotic zone, the small-sized scuticociliates dominate in the hypolimnion. Besides, species having symbionts and considered to be mixotrophic (Strobilidium gyrans, Strombidium viride, Stokesia vernalis) develop preferentially in the epilimnion and constitute more than 50% of the total ciliate biomass.