European Journal of Phycology Archimer http://www.ifremer.fr/docelec/ Volume 41, Number 3/August 2006 : 259-279 Archive Institutionnelle de l’Ifremer http://dx.doi.org/10.1080/09670260600804868 © 2006, MetaPress The original publication is available at http://www.tandf.co.uk/journals/ ailable on the publisher Web site Cyanobacterial populations that build ‘kopara’ microbial mats in Rangiroa, Tuamotu Archipelago, French Polynesia 1 2,* 3 3 Laurent Richert , Stjepko Golubic , Roland Le Guédès , Annie Hervé And Claude Payri1 1 Laboratoire d’Ecologie Marine, Université de la Polynésie Française, Papeete, Polynésie Française 2 Biological Science Center, Boston University, 5 Cummington Str., Boston, MA 00215, USA 3 IFREMER, Centre de Nantes, Laboratoire VP/PBA, BP 21105, 44311, Nantes, France blisher-authenticated version is av *: Corresponding author : Correspondence to: Stjepko Golubic, Tel.: (617) 353-2432. Fax.: (617) 353-6340. e-mail: [email protected] Abstract: Cyanobacterial populations, the primary producers and builders of ‘kopara’ microbial mats were studied in four selected ponds along the rim of the Rangiroa Atoll, French Polynesia using a polyphasic approach. Seven isolates were maintained in uni-cyanobacterial cultures, characterized morphotypically and phylogenetically by evaluating sequences of the 16S rRNA gene of about 620 base pairs in length. Cyanobacteria in natural populations were analyzed microscopically, characterized morphotypically, and compared with cultured strains. Three of the isolates were identified in the field samples: Lyngbya aestuarii, Johannesbaptistia pellucida and Chroococcus submarinus were present in the mats only as minor components, whereas the species of Schizothrix that dominated the mat community could not be cultured. The sequence of Johannesbaptistia pellucida is published for the first time. The phylogenetic and taxonomic relations are discussed on the basis of a reconstructed phylogenetic tree in relation to morphotypic characters. Sequences of Kopara isolates plot separately from those cultured from the lagoon of the neighbouring atoll Tikehau, ccepted for publication following peer review. The definitive pu indicating a narrow niche differentiation of benthic cyanobacterial taxa. The results support the application of a polyphasic approach to characterization, ecology and diversity of cyanobacteria. Keywords: culture, cyanobacteria, diversity, kopara, microbial ecology, microbial mats, phylogeny, polyphasic approach, 16S rRNA Please note that this is an author-produced PDF of an article a 1 New XML Template (2006) [15.6.2006–10:36pm] [1–21] {TANDF_FPP}TEJP/TEJP_A_180430.3d (TEJP) [First Proof] Eur. J. Phycol., (2006), 41(3): 1–21 Cyanobacterial populations that build ‘kopara’ microbial mats in Rangiroa, Tuamotu Archipelago, French Polynesia 5 LAURENT RICHERT1, STJEPKO GOLUBIC2, ROLAND LE GUE´DE` S3, ANNIE HERVE´3 AND CLAUDE PAYRI1 1Laboratoire d’Ecologie Marine, Universite´ de la Polyne´sie Franc¸ aise, Papeete, Polyne´sie Franc¸ aise 2Biological Science Center, Boston University, 5 Cummington Str., Boston, MA 00215, USA 3IFREMER, Centre de Nantes, Laboratoire VP/PBA, BP 21105, 44311, Nantes, France 10 (Received 24 December 2005; accepted 16 May 2006) Cyanobacterial populations, the primary producers and builders of ‘kopara’ microbial mats were studied in four selected ponds along the rim of the Rangiroa Atoll, French Polynesia using a polyphasic approach. Seven isolates were maintained in uni-cyanobacterial cultures, characterized morphotypically and phylogenetically by evaluating sequences of the 16S rRNA gene of about 620 base pairs in length. Cyanobacteria in natural populations were analysed microscopically, characterized 15 morphotypically, and compared with cultured strains. Three of the isolates were identified in the field samples: Lyngbya aestuarii, Johannesbaptistia pellucida and Chroococcus submarinus were present in the mats only as minor components, whereas the species of Schizothrix that dominated the mat community could not be cultured. The sequence of Johannesbaptistia pellucida is published for the first time. The phylogenetic and taxonomic relations are discussed on the basis of a reconstructed phylogenetic tree in relation to morphotypic characters. Sequences of Kopara isolates plot separately from those cultured from 20 the lagoon of the neighbouring atoll Tikehau, indicating a narrow niche differentiation of benthic cyanobacterial taxa. The results support the application of a polyphasic approach to characterization, ecology and diversity of cyanobacteria. Key words: culture, cyanobacteria, diversity, kopara, microbial ecology, microbial mats, phylogeny, polyphasic approach, 16S rRNA 25 Introduction 2001; Ru¨ tters et al., 2002; Abed et al., 2003a, b), et al Microbial mats are stratified communities estuaries (Mir ., 1991), hypersaline ponds et al et al arranged along steep vertical gradients of light, (Krumbein ., 1977), hot springs (Ward ., a oxygen, sulphide, Eh and pH, with each stratum 1994; Lopez-Cortes, 1999 ), and desert soils (Campbell et al., 1989; Garcia-Pichel et al., 2001). 50 dominated by specialized guilds of microorganisms A variety of shallow ponds on land rims of 30 (see Riding & Awramik, 2000; Krumbein et al., South Pacific atolls offer good conditions for 2003). The illuminated surface layers are domi- development of thick microbial mats called nated by microbial oxygenic and anoxigenic ‘kopara’ by cyanobacteria. This system of ponds phototrophs, separated by a sharp oxic-anoxic with variable water supply and a wide range of 55 boundary (Potts; 1980; Stal et al., 1985; Nicholson salinities provides a good model to study environ- 35 et al., 1987; Golubic, 1991), with chemolithotrophs mental preferences and differentiation of microbial distributed across this boundary (Jørgensen & communities. The study is relevant to our under- Gallardo, 1999). Under stress conditions, such as standing of similar ancient microbial systems. fluctuations in temperature, water supply and Possible fossil counterparts of ‘kopara’-type mats 60 salinity, cyanobacteria often remain unchallenged were recognized in Jurassic strata (Tribovillard 40 as the principal primary producers of microbial et al., 2000) and fossil microbial mats comprise mats (Golubic, 1994; Golubic et al., 2000). a significant part of the stromatolite fossil record, Microbial mat communities are encountered which dominated early Earth history. world wide in a variety of marine, freshwater and The biogeochemical properties of ‘kopara’ have 65 terrestrial environments, including marine subtidal been extensively studied with respect to relation- 45 and intertidal ranges (Golubic, 1985; Pearl et al., ships between organic compounds and mineraliza- Correspondence to: Stjepko Golubic, Tel.: (617) 353-2432. Fax.: tion processes (Trichet, 1967; De´ farge et al., (617) 353-6340. e-mail: [email protected] 1985, 1996; De´ farge & Trichet, 1990, 1993; ISSN 0967-0262 print/ISSN 1469-4433 online/06/030001–21 ß 2006 British Phycological Society DOI: 10.1080/09670260600804868 New XML Template (2006) [15.6.2006–10:36pm] [1–21] {TANDF_FPP}TEJP/TEJP_A_180430.3d (TEJP) [First Proof] L. Richert et al. 2 70 Trichet & De´ farge, 1997; Trichet et al., 2001). The role of proteinaceous compounds and amino acid composition in controlling calcification was stu- died in deeper layers of ‘kopara’ mats (Gautret & Trichet, 2005) and other microbialites (Gautret 75 et al., 2004). The formation of phosphorite deposits in ‘kopara’ was studied by Jehl & Rougerie (1995) and Rougerie et al. (1997). Exopolysaccharides were studied by Rougeaux et al. (2001) and recently, in conjunction with the 80 present investigation, by Richert et al. (2005). The ultrastructure of accumulated exopolymers (mostly polysaccharides) was studied using Cryoscan scan- Fig. 1. Rangiroa Atoll, Tuamotu Archipelago, French Polynesia with the locations of the studied ‘kopara’ ning electron microscopy (De´ farge et al., 1996), ponds. The neighbouring Tikehau Atoll is seen on the but only a few studies dealt with the microbial left. Modified from the NASA image. Scale bar: 10 km. 85 composition of ‘kopara’ mats using light micro- scopy (De´ farge et al., 1994a, b; Mao Che et al., 2001). The surface layers of ‘kopara’ are orange, dark blueish- This study deals with polyphasic characteriza- green or greyish-black depending on the prevailing tion of cyanobacterial populations of ‘kopara’ microorganisms, which, in turn, respond to the degree of wetness. Deeper layers are reddish-orange alternating 130 90 microbial mats as the principal primary producers with white layers encrusted with carbonate (De´ farge in four selected ponds in the north-western part of et al., 1985, Gautret & Trichet, 2005). the Rangiroa Atoll, by combining field observa- tions, microscopic analysis of natural populations and cultured isolates from these populations. Sampling 95 It explores the apparent and cryptic cyanobacterial The current study explored microbial composition in diversity in a series of tropical ponds. The mats in four ponds located in the northwestern part of 135 characterization assesses morphotypic and geno- the Rangiroa Atoll designated as R2, R59, R60 and R63 typic properties, the latter based on partial (Fig. 1). Pond R2, located on the islet Pavete, was (620 base pair [bp]) sequences of 16S rRNA gene. studied earlier by De´ farge et al. (1994a). Mao Che et al. (2001) studied ponds R2 and R59 and characterized their physical and chemical properties. The other two 140