MEPS 191:79-89 (1999)  -  doi:10.3354/meps191079

Annual sediment primary production and respiration in a large coral reef lagoon (SW New Caledonia)

Jacques Clavier1,*, Claire Garrigue2

1Institut de Recherche pour le Développement, Centre de Bretagne, BP 70, 29280 Plouzané, France
2Institut de Recherche pour le Développement, Centre de Nouméa, BP A5, 98848 Nouméa, New Caledonia
*Present address: Institut Universitaire Européen de la Mer, UMR 6539, Technopole Brest Iroise, Place Nicolas Copernic, 29280 Plouzané, France. E-mail:

ABSTRACT: Sediment photosynthetic production and community respiration were investigated for 1 yr in the south-west lagoon of New Caledonia (surface area: 2000 km2; mean depth: 21 m). Metabolic fluxes were measured at the water-sediment interface using benthic enclosures, at 60 sampling stations randomly distributed in space and time. Mean gross primary production (Pg) was 12.06 mol C m-2 yr-1. Mean respiration (R) was 13.68 mol C m-2 yr-1. Pg/R was thus 0.88, indicating that the whole lagoon was net heterotrophic. There were, however, large differences along a land-ocean gradient. Muddy bottoms (35% of the lagoon surface), located along the shore and in the deeper part of the lagoon, were significantly heterotrophic (Pg/R = 0.39), whereas the ratio for sandy bottoms (65% of the area) towards the reef were close to 1 or slightly positive, indicating potentially autotrophic benthic communities. Both Pg and R followed a similar seasonal variation with higher values during the warm season (November to February), when maximum irradiance and the particulate organic carbon supply occurred. These results suggest that autotrophy, generally observed in coral reef flats, may also occur in lagoon sediments, indicating both a major importance of regeneration processes and a relative equilibrium of energy exchanges with adjacent ecosystems. Terrestrial influence results in a decrease of autochthonous production and a correlative increase of carbon sedimentation leading to benthic heterotrophy.

KEY WORDS: Coral reef lagoon · Benthic community metabolism · Sediments

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