Distribution of greenhouse gases in hyper-arid and arid areas of northern Chile and the contribution of the high altitude wetland microbiome (Salar de Huasco, Chile)

Abstract

Northern Chile harbors different bioclimatic zones including hyper-arid and arid ecosystems and hotspots of microbial life, such as high altitude wetlands, which may contribute differentially to greenhouse gases (GHG) such as carbon dioxide (CO), methane (CH) and nitrous oxide (NO). In this study, we explored ground level GHG distribution and the potential role of a wetland situated at 3800 m.a.s.l, and characterized by high solar radiation < 1600 W m, extreme temperature ranges (-12 to 24 °C) and wind stress (< 17 m s). The water source of the wetland is mainly groundwater springs, which generates streams and ponds surrounded by peatlands. These sites support a rich microbial aquatic life including diverse bacteria and archaea communities, which transiently form more complex structures, such as microbial mats. In this study, GHG were measured in the water and above ground level air at the wetland site and along an elevation gradient in different bioclimatic areas from arid to hyper-arid zones. The microbiome from the water and sediments was described by high-throughput sequencing 16S rRNA and rDNA genes. The results indicate that GHG at ground level were variable along the elevation gradient potentially associated with different bioclimatic zones, reaching high values at the high Andean steppe and variable but lower values in the Atacama Desert and at the wetland. The water areas of the wetland presented high concentrations of CH and CO, particularly at the spring areas and in air bubbles below microbial mats. The microbial community was rich (> 40 phyla), including archaea and bacteria potentially active in the different matrices studied (water, sediments and mats). Functional microbial groups associated with GHG recycling were detected at low frequency, i.e., < 2.5% of total sequences. Our results indicate that hyper-arid and arid areas of northern Chile are sites of GHG exchange associated with various bioclimatic zones and particularly in aquatic areas of the wetland where this ecosystem could represent a net sink of NO and a source for CH and CO.

Virus and Potential Host Microbes from Viral-Enriched Metagenomic Characterization in the High-Altitude Wetland, Salar de Huasco, Chile

“…Supporting the patterns of taxonomic relative abundance presented in both sites, greater diversity and evenness was observed in H0 compared to H3 ( Table 2 ). These observations are comparable to what was previously reported for pond sites in the same area during previous studies [ 13 , 45 ], where the highest alpha diversity indexes (i.e., Shannon index) were observed in ponds compared to waterways. Using a k-mer sequence similarity measure, we calculated that only 12.2% of contigs in the “unclassified” category from Figure 2 were shared between metagenomes, further highlighting the different in community composition between these two sites.…”

“…Salinity was in the range of fresh water according to [ 44 ], which characterizes water sources as fresh when conductivity is <800 μS cm −1 ( Table 1 ). These chemical characteristics were similar to those sampled during February 2012, November 2014 and March 2015 in Salar de Huasco [ 13 , 45 ]. VLP and picoplankton abundance were very similar in the H0 and H3 sites while VPR was slightly higher in H0 ( Table 1 ).…”

“…Therefore, the percentage of unassigned sequences found in the sampling sites ( Figure 3 ) might be overestimated. Unfortunately, there are no previous studies to compare viral diversity in high-altitude wetlands for the Altiplano area, but based on results of the prokaryotic community in our study and in others, there were a significant number of unclassified taxa, up to 56% in some cases [ 6 , 13 , 14 , 45 ], suggesting a high number of novel microbial groups and their viruses that are yet to be characterized.…”

“…These values were lower than the ones observed in wet season, February 2012 [ 13 ] where the order of magnitude for VLP and picoplankton abundance was 10 7 –10 8 VLP mL −1 and 10 5 –10 6 cells mL −1 , and the VPR was 67 and 2 for H0 and H3, respectively. Instead, during the sampling in November 2014 and March 2015, VLP (10 5 VLP mL −1 ) and picoplankton (10 4 –10 5 cells mL −1 ) abundance was lower than the ones report here, but VPR were similar to H0 (i.e., 9.4 and 13.2 for H0 spring and H3 spring, respectively) [ 45 ]. As reported in [ 13 ], where microbial mats were present, a higher abundance of picoplankton and VLP was observed, and this was also associated with higher microbial diversity and community complexity in ponds when compared with water sources or lagoon sites.…”

“…Interestingly, cyanophages were in low relative abundance in both sites but over twice as prevalent in H3, suggesting that virus–host dynamics might be influencing Cyanobacteria abundance over time in the ponds. Molina et al [ 45 ] reported the three main abundant phyla of bacteria as Proteobacteria, Cyanobacteria and Bacteroidetes, and the abundant Archaeal phyla as Crenarchaeota, Parvarchaeota and Euryarchaeota based on 16S rDNA gene sequences. In contrast to our similar results for bacterial populations, these Archaeal phyla were relatively rare during November 2014 and March 2015 for H0 and H3 (<0.72%).…”