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The Great Salt Plains (GSP) in north-central Oklahoma, USA is an expansive salt flat (approximately 65 km(2)) that is part of the federally protected Salt Plains National Wildlife Refuge. The GSP serves as an ideal environment to study the microbial diversity of a terrestrial, hypersaline system that experiences wide fluctuations in freshwater influx and diel temperature. Our study assessed cyanobacterial diversity at the GSP by focusing on the taxonomic and physiological diversity of GSP isolates, and the 16S rRNA phylogenetic diversity of isolates and environmental clones from three sites (north, central, and south). Taxonomic diversity of isolates was limited to a few genera (mostly Phormidium and Geitlerinema), but physiological diversity based on halotolerance ranges was strikingly more diverse, even between strains of the same phylotype. The phylogenetic tree revealed diversity that spanned a number of cyanobacterial lineages, although diversity at each site was dominated by only a few phylotypes. Unlike other hypersaline systems, a number of environmental clones from the GSP were members of the heterocystous lineage. Although a number of cyanobacterial isolates were close matches with prevalent environmental clones, it is not certain if these clones reflect the same halotolerance ranges of their matching isolates. This caveat is based on the notable disparities we found between strains of the same phylotype and their inherent halotolerance. Our findings support the hypothesis that variable or poikilotrophic environments promote diversification, and in particular, select for variation in ecotype more than phylotype.

We studied the algal community of the Great Salt Plains (GSP), an expansive (65 km2) salt flat situated in north-central Oklahoma, USA that has been designated as the Salt Plains Microbial Observatory (SPMO) by the National Science Foundation. The GSP offered a unique opportunity to study a terrestrial, hypersaline algal community that experiences wide-ranging environmental conditions. We were able to show that ammonium-N, rather than salinity, was the most important predictor of total algal biomass. However, salinity was found to be a significant controlling variable in diatom distribution at the GSP, where diatom abundance was negatively correlated with porewater salinity concentrations. Overall, chlorophytes (likely dominated by Dunaliella spp.) were the most abundant algal group at the consistently hypersaline (>300 ppt) south site. Diatom and cyanobacterial biomass were on average highest at the central site, which experienced greater fluctuations in salinity. While taxonomic diversity was limited to three algal groups (chlorophytes, diatoms, and cyanobacteria), the salinity preferences and halotolerance ranges of isolated strains were quite variable. Although porewater salinities at the GSP are commonly near saturation (>300 ppt), the large majority of isolates had halotolerance ranges below 150 ppt. This suggests that algae at the GSP rarely achieve maximum growth rates, and could only do so when intermittent rain events reduce salinity to optimal levels. Because the vast majority of our strains were isolated from salt-saturated soil samples, maintaining viability (rather than growth efficiency) appears to be the most successful adaptation to the extreme conditions at the GSP. [ABSTRACT FROM AUTHOR]

Pulp and paper secondary waste-treatment systems in Brazil, Canada, New Zealand, and the U.S.A. contained dynamic cyanobacterial communities, some of which exceeded heterotrophic bacterial biomass. No other viable photoautotrophic populations were detected in the ponds. Regardless of geographical location, Oscillatoriales including Phormidium, Geitlerinema, and Pseudanabaena were the dominant taxa. As well, Chroococcus (Chroococcales) was an important genus in Brazil and New Zealand. The possible impact of cyanobacteria on waste-treatment efficiency deserves further study given their large biomass and diverse metabolic characteristics.Key words: cyanobacteria, blue-green algae, heterotrophic bacteria, community structure, pulp and paper secondary waste treatment.On a observé au Brésil, au Canada, en Nouvelle-Zélande et aux États-Unis que les systèmes de traitement secondaire des rejets d'usines de pâtes et papiers contenaient des populations dynamiques de cyanobactéries dont certaines dépassent même les valeurs de la biomasse bactérienne hétérotrophe. Aucune autre population de photoautotrophes n'a été détectée dans les bassins. Indépendamment de la localisation géographique, les taxons dominants appartenaient aux Oscillatoriales incluant Phormidium, Geitlerinema et Pseudanabaena. Au Brésil et en Nouvelle-Zélande Chroococcus (Chroococcales) était aussi un genre important. L'impact potentiel des cyanobactéries sur l'efficacité du traitement des rejets mérite d'être étudié plus à fond, compte tenu de la biomasse élevée et des caractéristiques métaboliques variées de ces bactéries.Mots clés : cyanobactéries, algues bleues-vertes, bactéries hétérotrophes, organisation de la population, traitement secondaire des rejets d'usines de pâtes et papiers.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]