Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group

Blanes, Spain

Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group

Blanes, Spain
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Triado-Margarit X.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Casamayor E.O.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group
Environmental Microbiology | Year: 2012

The genetic diversity of planktonic eukaryotic microorganisms (size range 3-40μm) inhabiting 11 alpine lakes of the Central Pyrenees (Spain) was analysed by cloning and sequencing of the 18S rRNA gene. The selected lakes covered a wide range of environmental conditions representative of the regional landscape heterogeneity. Overall, we obtained 953 sequences (averaged length 750bp) that were grouped in 343 representative OTUs (98% identity). The genetic richness was high, and the 18S rRNA gene sequences spread within nine high-rank taxonomic groups and grouped in 26 eukaryal classes. Most of the sequences affiliated with Stramenopiles (>55% of total sequences, mostly Chrysophyceae), Cryptophyta and Alveolata (15% each). Three groups had relative abundance <5%, i.e. Opisthokonta (mostly Fungi), Viridiplantae (mostly Chlorophyceae) and Rhizaria (cercomonads). Finally, minor groups were related to Katablepharidophyta, Euglenozoa and Telonemida. The lakes showed a different community structure being pH, and phosphorous and Chl a concentrations the main environmental drivers. The novelty level was high, and a quarter of the retrieved OTUs were notably divergent (<97% identity) from any previously known sequence, mainly for Rhizaria and Opisthokonta. More than 50% of the sequences affiliated with clusters exclusively formed by uncultured protists. Cryptophyta and Viridiplantae showed the largest number of sequences closely related to cultured counterparts. This work is the first description of the genetic diversity of eukaryotic assemblages in ultraoligotrophic high mountain lakes, and the study unveils alpine environments as an important reservoir of microbial eukaryotic biodiversity. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.


Llorens-Mares T.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Auguet J.-C.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Casamayor E.O.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group
Environmental Microbiology Reports | Year: 2012

Bacterial community composition was analysed in the slush layers of snow-covered Lake Redon (2240m altitude, Limnological Observatory of the Pyrenees, LOOP, NE Spain) in winter and spring and compared with bacteria from the lake water column, using 16S rRNA gene clone libraries and CARD-FISH counts. The set of biological data was related to changes in bacterial production and to other relevant environmental variables measured in situ. In winter, up to 70% of the 16S rRNA sequences found in the slush were closely related to planktonic bacteria from the water column beneath the ice. Conversely, during spring ablation, 50% of the sequences had >97% identity with bacteria from the cryosphere (i.e. globally distributed glaciers, snow and ice) and may have originated from remote aerosol deposition. The transition winter to spring was characterized by consistent community changes switching from assemblages dominated by Betaproteobacteria, Verrucomicrobia and Bacteroidetes during snowpack growth to communities essentially dominated by the Bacteroidetes of classes Cytophagia and Sphingobacteria. This strong bacterial composition switch was associated with consistent increases in bacterial abundance and production, and decreasing bacterial diversity. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.


Auguet J.-C.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Nomokonova N.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Camarero L.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group | Casamayor E.O.,Limnological Observatory of the Pyrenees LOOP Biogeodynamics and Biodiversity Group
Applied and Environmental Microbiology | Year: 2011

The annual changes in the composition and abundance of ammonia-oxidizing archaea (AOA) were analyzed monthly in surface waters of three high mountain lakes within the Limnological Observatory of the Pyrenees (LOOP; northeast Spain) using both 16S rRNA and functional (ammonia monooxygenase gene, amoA) gene sequencing as well as quantitative PCR amplification. The set of biological data was related to changes in nitrogen species and to other relevant environmental variables. The whole archaeal assemblage was dominated by phylotypes closely related to the crenarchaeal 1.1a group (58% ± 18% of total 16S rRNA gene sequences), and consistent structural changes were detected during the study. Water temperature was the environmental variable that better explained spring, summer, and winter (ice-covered lakes) archaeal assemblage structure. The amoA gene was detected year round, and seasonal changes in amoA gene composition were well correlated with changes in the archaeal 16S rRNA gene pool. In addition, copy numbers of both the specific 1.1a group 16 rRNA and archaeal amoA genes were well correlated, suggesting that most freshwater 1.1a Crenarchaeota had the potential to carry out ammonia oxidation. Seasonal changes in the diversity and abundance of AOA (i.e., amoA) were better explained by temporal changes in ammonium, the substrate for nitrification, and mostly nitrite, the product of ammonia oxidation. Lacustrine amoA gene sequences grouped in coherent freshwater phylogenetic clusters, suggesting that freshwater habitats harbor typical amoA-containing ecotypes, which is different from soils and seas. We observed within the freshwater amoA gene sequence pool a high genetic divergence (translating to up to 32% amino acid divergence) between the spring and the remaining AOA assemblages. This suggests that different AOA ecotypes are adapted to different temporal ecological niches in these lakes. © 2011, American Society for Microbiology.

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