AME 15:25-37 (1998)  -  doi:10.3354/ame015025

Trophic coupling between bacterial and phytoplanktonic compartments in shallow tropical reservoirs (Ivory Coast, West Africa)

Marc Bouvy1,*, Robert Arfi2, Philippe Cecchi3, Daniel Corbin3, Marc Pagano2, Lucien Saint-Jean2, Serge Thomas3

1ORSTOM/Departamento de Pesca, Universidade Federal Rural de Pernambouco, Rua D. Manoel de Medeiros - S/N Dois Irmaoes, 52171 030 Recife, PE, Brazil
2CRO/ORSTOM, BP V18, Abidjan, Ivory Coast
3ORSTOM, BP 1434, Bouaké 01, Ivory Coast

Biomass and production of bacterial and phytoplanktonic communities were measured during diurnal cycles at different stations in 3 shallow tropical reservoirs (Ivory Coast). Investigations were conducted in 1995 during 2 typical hydrological seasons (dry season in March and following rainy season in December). Bacterial production in the plankton ranged from 1.2 to 26.2 μg C l-1 h-1 and bacterial biomass ranged from 11 to 163 μg C l-1. A slope of 0.625 (n = 93) for the regression of log-transformed bacterial biomass versus log-transformed production suggests that the bacteria were strongly controlled by bottom-up processes. Ratios between net primary production and bacterial production averaged 67% (range 38 to 140%), indicating that the reservoirs studied can be considered as meso-eutrophic ecosystems. Average bacterial carbon demand corresponded to 97% of the net primary production, suggesting that the biological systems studied are based on autotrophic metabolism. These relationships are the result of a close metabolic coupling between bacterioplankton and phytoplankton, with a large fraction of primary production routed through heterotrophic bacteria and the microbial loop.

Bacteria · Phytoplankton · Eutrophication · Tropical reservoirs

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