Abstracts
Résumé
La production primaire phytoplanctenique et l'activité hétérotrophe bactérienne ont été étudiées parallèlement sur le lac d'AYDAT en 1985. L'activité photosynthétique, mesurée au alentours du midi solaire évolue entre 10 et 141 mg C m-2h-1, le maximum étant atteint en juillet. La vitesse maximale, V max, d'assimilation de glucose par les bactéries, (en présence de concentrations de traceur non limitantes) se situe entre 0,06 - 1,26 mg C m-2h-1. Le compartiment phytoplanctonique, de par sa production, semble être l'un des éléments régulateurs de l'activité hétérotrophe bactérienne en zone épilimnique.
Mots-clés:
- lac,
- phytoplancton,
- bactéries,
- production primaire,
- activité hétérotrophe
Abstract
The seasonal distributions of phytoptanktonic primary production and bacterial heterotrophicpotentials (using respectivey 14C and 14Glucose incorporations) were studied in a eutrophic lake (Lake Aydat, Massif Central, France).
Primary production and bacterial heterotrophic potentials vary respectively from 10 to 141 mg.C.m-2h-1 and from 0,06 to 1,26 mg.C.m-2h-1.
The comparative evolution of these two activities in relation to the temperature shows that the general idea about "the temperature - bacterial development" model seems to be insufficient when the investigation takes place in a complex ecosystem such as Lake Aydat. Indeed, the phytoplanktonic compartment, apart from its production, seems to be one of the regulating elements of the heterotrophic bacterial activity whose variations cannot be explained by changes in temperature alone.
In spite of the significant correlation obtained between bacterial activity and temperature, we should consider that the influence of this abiotic parameter on the bacterial development is an indirect one.
Keywords:
- Lake,
- phytoplankton,
- bacteria,
- primary production,
- heterotrophic activity
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