Picocyanobacterial assemblages in ultraoligotrophic Andean lakes reveal high regional microdiversity

Abstract

Picocyanobacteria (Pcy) diversity was studied in a set of ultraoligotrophic North Patagonian Andean lakes. The glacial lake system includes a central lake (Lake Nahuel Huapi, with its side basin, Lake Moreno) and four satellite lakes (Lakes Espejo, Correntoso, Gutiérrez and Mascardi) derived from a larger paleolake. Automated ribosomal intergenic spacer analysis showed a Pcy community structure composed of 18 operational taxonomic units (OTUs), of which only one (OTU 1094) was widely distributed, being found at all depths in all of the lakes. Most of the others were observed in a few of the lakes. The principal component analysis revealed the habitat specificity of some Pcy OTUs: the satellite lakes have a highly irradiated epilimnion, while the central lake has a well-mixed euphotic zone that does not extend beyond the epilimnion. We also observed a distinctive vertical distribution of the OTUs and a significant correlation between Pcy chlorophyll-specific primary production and OTU 738, which was only found in the satellite lakes. Lastly, the high ß-diversity of this lake district supports the hypothesis that microdiversity is higher in glacier-derived lake systems where habitat fragmentation due to geographic barriers results in rapid speciation. I N T RO D U C T I O N Picocyanobacteria (Pcy) play a fundamental role in oligotrophic water systems, contributing up to 80% of the total primary production (Bell and Kalff, 2001; Richardson and Jackson, 2007; Callieri, 2008). Pcy are the dominant picophytoplankters in ultraoligotrophic lakes, and are mainly represented by the genus Synechococcus (Stockner et al., 2000; Callieri et al., 2007b). The study of their genetic diversity has received much less attention than marine Pcy, and has been restricted to cultured strains (

Community Structure and Biogeochemical Impacts of Microbial Life on Floating Pumice

“…Indeed, 8 of the total 84 bacterial orders observed in the water column at least five times were not detected in the pumice samples. The order most underrepresented on pumice relative to the water column was family II, cyanobacteria (data not shown), consistent with the low representation of photoautotrophs on pumice observed at the phylum level and with the previously documented abundance of members of this group (e.g., Synechococcus) in the water columns of these lakes (23). Analysis at the genus level revealed strong habitat preferences consistent with the higher taxonomic levels (Fig.…”

Genetic and phenotypic differentiation among Galaxias maculatus populations in a Patagonian postglacial lake system

“…Accordingly, a remarkably high density of galaxiid larvae performing diel movements was observed using hydroacoustic methods in the limnetic zone of a similar lake in the region (Rechencq et al ., ). In addition, picocyanobacteria in the Nahuel Huapi Lake also exhibit very limited spatial structuring (Caravati et al ., ), suggesting this lake can be characterized as having a well mixed limnetic zone where larvae can mix.…”

Stable isotope analysis of trophic structure, energy flow and spatial variability in a large ultraoligotrophic lake in Northwest Patagonia

“…1), is an ultraoligotrophic system with a mean annual Secchi depth of 12 m, euphotic zone (Z 1% ) that extends to 48.8 m, total phosphorus of 5.1 μg L − 1 , and chlorophyll a of 0.6 μg L −1 (Alcalde et al, 1999;Caravati et al, 2010). Like all the lakes in Andean Patagonia, Lake Nahuel Huapi is of glacial origin and has been classified as warm monomictic with summer stratification (Quirós and Drago, 1985;Diaz et al, 2007).…”