Dinitrogen-fixing cyanobacteria in microbial mats of two shallow reef ecosystems

Dinitrogen-fixing organisms in cyanobacterial mats were studied in two shallow coral reef ecosystems: La Reunion Island, southwestern Indian Ocean, Sesoko (Okinawa) Island, and northwestern Pacific Ocean. Rapidly expanding benthic miniblooms, frequently dominated by a single cyanobacterial taxon, we...

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Bibliographic Details
Published in:Microbial ecology 2010-01, Vol.59 (1), p.174-186
Main Authors: Charpy, L, Palinska, KA, Casareto, B, Langlade, MJ, Suzuki, Y, Abed, RMM, Golubic, S
Format: Article
Language:English
Subjects:
Anabaena
Hydrocoleum
Hydrocoleum lyngbyaceum
Leptolyngbya
Oscillatoria bonnemaisonii
Phormidium
Symploca hydnoides
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Summary:Dinitrogen-fixing organisms in cyanobacterial mats were studied in two shallow coral reef ecosystems: La Reunion Island, southwestern Indian Ocean, Sesoko (Okinawa) Island, and northwestern Pacific Ocean. Rapidly expanding benthic miniblooms, frequently dominated by a single cyanobacterial taxon, were identified by microscopy and molecular tools. In addition, nitrogenase activity by these blooms was measured in situ. Dinitrogen fixation and its contribution to mat primary production were calculated using super(15)N sub(2) and super(13)C methods. Dinitrogen-fixing cyanobacteria from mats in La Reunion and Sesoko showed few differences in taxonomic composition. Anabaena sp. among heterocystous and Hydrocoleum majus and Symploca hydnoides among nonheterocystous cyanobacteria occurred in microbial mats of both sites. Oscillatoria bonnemaisonii and Leptolyngbya spp. occurred only in La Reunion, whereas Hydrocoleum coccineum dominated in Sesoko. Other mats dominated by Hydrocoleum lyngbyaceum, Phormidium laysanense, and Trichocoleus tenerrimus occurred at lower frequencies. The 24-h nitrogenase activity, as measured by acetylene reduction, varied between 11 and 324 nmoles C sub(2)H sub(2) redeuced kg super(-1) Chl a. The highest values were achieved by heterocystous Anabaena sp. performed mostly during the day. Highest values for nonheterocystous cyanobacteria were achieved by H. coccineum mostly during the night. Daily nitrogen fixation varied from nine (Leptolyngbya) to 238 nmoles N sub(2)kg super(-1) Chl day super(-1) super( )(H. coccineum). Primary production rates ranged from 1,321 (S. hydnoides) to 9,933 nmoles C kg super(-1) Chl day super(-1) (H. coccineum). Dinitrogen fixation satisfied between 5% and 21% of the nitrogen required for primary production. [Study location for Reunion Island was at La Saline.]
ISSN:0095-3628
1432-184X
DOI:10.1007/s00248-009-9576-y