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Aquatic Microbial Ecology

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AME 47:73-81 (2007)  -  doi:10.3354/ame047073

Benthic nitrogen fixation in the SW New Caledonia lagoon

Loïc Charpy1,*, Romain Alliod1, Martine Rodier2, Stjepko Golubic3

1IRD, UR167 COM, Rue de la Batterie des Lions, 13007 Marseille, France
2IRD, COM, Laboratoire d’Océanographie et de Biogéochimie, Faculté des Sciences de Luminy, Case 901, 13288 Marseille Cedex 09, France
3Department of Biology, Boston University, 5 Cummington Street, Boston, Massachusetts 02215, USA

ABSTRACT: Various types of microbial mats are widespread in the SW New Caledonia lagoon. Both heterocystous (Nodularia harveyana) and non-heterocystous (Hydrocoleum cantharidosmum, H. lyngbyaceum) cyanobacteria dominate these mats. Using the acetylene reduction technique, nitrogenase activity was observed at all sites. Heterocystous cyanobacteria fix N2 during the daytime, whereas non-heterocystous cyanobacteria fix N2 during the night. The intensity of nitrogenase activity depended on the level of light energy received during daylight. An estimation of nitrogen fixation by benthic cyanobacteria (16.4 ± 5.4 mg N2 m–2 d–1) at 21 m depth (average depth of the lagoon) represented 19% of the nitrogen requirement for benthic primary production.

KEY WORDS: Nodularia · Hydrocoleum · Microbial mats · Nitrogen fixation · Coral · Reef lagoon

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