AME 21:203-209 (2000)  -  doi:10.3354/ame021203

Enhancement of pico- and nanoplankton growth by coral exudates

C. Ferrier-Pagès1,*, N. Leclercq1, J. Jaubert1, S. P. Pelegrí2,**

1Observatoire Océanologique Européen, Centre Scientifique de Monaco, Av. Saint-Martin, 98000 Monaco (Principality of Monaco)
2Observatoire Océanologique, Marine Microbial Ecology Group, ESA 7076 CNRS, BP 28, 06234 Villefranche-sur-Mer cedex, France
*E-mail: **Present address: Laboratoire d¹Océanographie et de Biogéochimie, UMR 6535 CNRS, Campus de Luminy, Case 901, 163 Avenue de Luminy, 13288 Marseille cedex 9, France

ABSTRACT: The enhancement of pico- and nanoplankton cell biomass by coral exudates was studied in the laboratory. Two types of mesocosms were used, the first one containing only a carbonate sand layer (control mesocosm) and the second one containing a coral layer over the carbonate sand layer (coral mesocosm). During 10 h incubations, we followed the concentration of bacteria, cyanobacteria, and of auto- and heterotrophic flagellates, as well as the concentrations of inorganic (N and P) and organic (dissolved organic carbon, DOC) nutrients. There were no significant differences in inorganic nutrient concentrations between mesocosms. However, DOC concentrations in coral mesocosms exhibited peaks 5- to 13-fold higher than control mesocosm levels; these peaks took place between 13:00 and 17:00 h and lasted for ca 2 h. As a consequence, microbial growth was significantly enhanced in coral mesocosms. At the end of the incubations, bacterial biomass was 6-fold higher in coral relative to control mesocosms. Autotrophic biomass was 3 to 5 times higher in coral mesocosms. These results indicate that small amounts of coral exudates (0.5 to 10% of maximum DOC concentrations) are enough to greatly stimulate microbial growth.

KEY WORDS: Picoplankton · Nanoplankton · Corals · Organic carbon (DOC) · Mesocosm

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