Che L.M. auteur aut IRD Andréfouët Serge auteur aut IRD Bothorel V. auteur aut IRD Guezennec M. auteur aut IRD Rougeaux H. auteur aut IRD Guezennec J. auteur aut IRD Deslandes E. auteur aut IRD Trichet J. auteur aut IRD Matheron R. auteur aut IRD Campion T.L. auteur aut IRD Payri C. auteur aut IRD Caumette P. auteur aut IRD text journalArticle eng text/pdf born digital access Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20-40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2-3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats. specialized POLYNESIE FRANCAISE PACIFIQUE 064GEOCHI 47 11 994-1012 2001 0008-4166 https://www.documentation.ird.fr/hor/fdi:010089986 10.1139/w01-106 0008-4166 [F B010089986] https://www.documentation.ird.fr/hor/fdi:010089986 https://www.documentation.ird.fr/intranet/publi/2024-08/010089986.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2024-05-15 2024-08-07 fdi:010089986 fre