AME 22:215-226 (2000)  -  doi:10.3354/ame022215

Heterotrophic protists as a trophic link between picocyanobacteria and the pearl oyster Pinctada margaritifera in the Takapoto lagoon (Tuamotu Archipelago, French Polynesia)

Pascale Loret1,*, Solange Le Gall2, Christine Dupuy2,3, Jean Blanchot4, Annie Pastoureaud2, Bruno Delesalle1, Xavier Caisey5, Gérard Jonquières5

1EPHE, URA-CNRS 1453, Université de Perpignan, 66860 Perpignan Cédex, France
2CREMA, BP 5, 17137 L¹Houmeau, France
3LBEM, Université de La Rochelle, Pôle Science, Avenue Michel Crépeau, 17042 La Rochelle, France
4IRD, Station Biologique de Roscoff, BP 74, 29682 Roscoff, France
5IFREMER/COP, BP 7004 Taravao, Tahiti, French Polynesia
*Present address: Department of Oceanography, Texas A&M University, 3146 TAMU, College Station, Texas 77843-3146, USA. E-mail:

ABSTRACT: Pearl oysters are farmed in oligotrophic tropical atoll lagoons where planktonic communities are dominated by production from cyanobacteria smaller than 2 μm. Paradoxically, the pearl oyster Pinctada margaritifera only retains particles larger than 2 μm. In this study, we assess the relative contribution of hetero/mixotrophic microbiota to the available planktonic resource. In Takapoto Atoll, picocyanobacteria are the dominant biomass (20 μg C l-1). The carbon biomass of ciliates and dinoflagellates ranges from 1 to 24 and 0.5 to 5 μg C l-1 respectively, with a mean of 6 μg C l-1 for ciliates and 2 μg C l-1 for dinoflagellates. The possible retention by P. margaritifera on a natural protist suspension was investigated. Due to its high clearance rates (ca 20 l h-1 g-1) the pearl oyster retained 85 μg C h-1 g-1 from ciliates and 65 μg C h-1 g-1 from dinoflagellates. Conversely, cyanobacteria were not efficiently retained by the bivalve and did not efficiently contribute to its diet. From our experiments, we concluded that hetero/mixotrophic protists rapidly and efficiently process the picoplanktonic resource towards filter-feeders, particularly pearl oysters.

KEY WORDS: Protists · Atoll lagoon · Pearl oysters · Pinctada margaritifera · Picoplankton · Trophic resource

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