Short-term characterisation of climatic-environmental variables and microbial community diversity in a high-altitude Andean wetland (Salar de Huasco, Chile).

Microbial community structures are shaped by geochemical factors and their interactions with the lithosphere, hydrosphere, and atmosphere through the processes of chemical mobilisation and mineralisation. High-altitude wetlands and salt flats in the central Andes are characterised by pronounced physicochemical gradients and extreme climatic conditions, representing hotspots of microbial diversity. We here hypothesise about the existence of direct relationships between the local microbiology and the climate cyclicity variables based on meteorological and biogeochemical patterns that develop over a short time scale (five years). We have here analysed the interactions between hydrometeorological and biogeochemical variables and the microbial communities of the Salar de Huasco. These results were obtained by correlating 16S cDNA and DNA gene Illumina sequences with meteorological/satellite data collected both at monitoring stations and by remote sensing between the years 2015 and 2020. The precipitation levels and flooded areas (i.e., areas covered and/or saturated with permanent water) detected in the Salar de Huasco revealed a marked hydric cyclicity that correlated seasonally with intra-annual wet and dry seasons. Overall, at this site, wet periods occurred from December to April, and dry periods from May to November. Meteorological variables such as solar radiation, air temperature, relative humidity, wind speed, atmospheric pressure, and wind direction were well-defined, showing a potential association with the hydrogeology of the area, which is directly related to the wetlands' flooded areas. Finally, the microbial presence and potentially active microbial communities were determined through the sequencing of the 16S gene (DNA and cDNA, respectively), this were associated with climatic seasonality and spatially distributed physical and chemical heterogeneity. Other non-local inter-annual scale processes, such as El Niño-Southern Oscillation (ENSO) events, modify the physical and chemical context of the wetland, thus forming unique ecological niches in the Andean Mountains.

Dissolved greenhouse gases and benthic microbial communities in coastal wetlands of the Chilean coast semiarid region.

Coastal wetlands are ecosystems associated with intense carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) recycling, modulated by salinity and other environmental factors that influence the microbial community involved in greenhouse gases production and consumption. In this study, we evaluated the influence of environmental factors on GHG concentration and benthic microbial community composition in coastal wetlands along the coast of the semiarid region. Wetlands were situated in landscapes along a south-north gradient of higher aridity and lower anthropogenic impact. Our results indicate that wetlands have a latitudinal variability associated with higher organic matter content at the north, especially in summer, and higher nutrient concentration at the south, predominantly in winter. During our sampling, wetlands were characterized by positive CO2 µM and CH4 nM excess, and a shift of N2O nM excess from negative to positive values from the north to the south. Benthic microbial communities were taxonomically diverse with > 60 phyla, especially in low frequency taxa. Highly abundant bacterial phyla were classified into Gammaproteobacteria (Betaproteobacteria order), Alphaproteobacteria and Deltaproteobacteria, including key functional groups such as nitrifying and methanotrophic bacteria. Generalized additive model (GAM) indicated that conductivity accounted for the larger variability of CH4 and CO2, but the predictions of CH4 and CO2 concentration were improved when latitude and pH concentration were included. Nitrate and latitude were the best predictors to account for the changes in the dissolved N2O distribution. Structural equation modeling (SEM), illustrated how the environment significantly influences functional microbial groups (nitrifiers and methane oxidizers) and their resulting effect on GHG distribution. Our results highlight the combined role of salinity and substrates of key functional microbial groups with metabolisms associated with both carbon and nitrogen, influencing dissolved GHG and their potential exchange in natural and anthropogenically impacted coastal wetlands.

Virus-to-prokaryote ratio in the Salar de Huasco and different ecosystems of the Southern hemisphere and its relationship with physicochemical and biological parameters.

The virus-to-prokaryote ratio (VPR) has been used in many ecosystems to study the relationship between viruses and their hosts. While high VPR values indicate a high rate of prokaryotes' cell lysis, low values are interpreted as a decrease in or absence of viral activity. Salar de Huasco is a high-altitude wetland characterized by a rich microbial diversity associated with aquatic sites like springs, ponds, streams and a lagoon with variable physicochemical conditions. Samples from two ponds, Poza Rosada (PR) and Poza Verde (PV), were analyzed by epifluorescence microscopy to determine variability of viral and prokaryotic abundance and to calculate the VPR in a dry season. In addition, to put Salar de Huasco results into perspective, a compilation of research articles on viral and prokaryotic abundance, VPR, and metadata from various Southern hemisphere ecosystems was revised. The ecosystems were grouped into six categories: high-altitude wetlands, Pacific, Atlantic, Indian, and Southern Oceans and Antarctic lakes. Salar de Huasco ponds recorded similar VPR values (an average of 7.4 and 1.7 at PR and PV, respectively), ranging from 3.22 to 15.99 in PR. The VPR variability was associated with VA and chlorophyll a, when considering all data available for this ecosystem. In general, high-altitude wetlands recorded the highest VPR average (53.22 ± 95.09), followed by the Oceans, Southern (21.91 ± 25.72), Atlantic (19.57 ± 15.77) and Indian (13.43 ± 16.12), then Antarctic lakes (11.37 ± 15.82) and the Pacific Ocean (6.34 ± 3.79). Physicochemical variables, i.e., temperature, conductivity, nutrients (nitrate, ammonium, and phosphate) and chlorophyll a as a biological variable, were found to drive the VPR in the ecosystems analyzed. Thus, the viral activity in the Wetland followed similar trends of previous reports based on larger sets of metadata analyses. In total, this study highlights the importance of including viruses as a biological variable to study microbial temporal dynamics in wetlands considering their crucial role in the carbon budgets of these understudied ecosystems in the southern hemisphere.

Spatial co-occurrence patterns of benthic microbial assemblage in response to trace metals in the Atacama Desert Coastline.

Taxonomic and functional microbial communities may respond differently to anthropogenic coastal impacts, but ecological quality monitoring assessments using environmental DNA and RNA (eDNA/eRNA) in response to pollution are poorly understood. In the present study, we investigated the utility of the co-occurrence network approach's to comprehensively explore both structure and potential functions of benthic marine microbial communities and their responses to Cu and Fe fractioning from two sediment deposition coastal zones of northern Chile via 16S rRNA gene metabarcoding. The results revealed substantial differences in the microbial communities, with the predominance of two distinct module hubs based on study zone. This indicates that habitat influences microbial co-occurrence networks. Indeed, the discriminant analysis allowed us to identify keystone taxa with significant differences in eDNA and eRNA comparison between sampled zones, revealing that Beggiatoaceae, Carnobacteriaceae, and Nitrosococcaceae were the primary representatives from Off Loa, whereas Enterobacteriaceae, Corynebacteriaceae, Latescibacteraceae, and Clostridiaceae were the families responsible for the observed changes in Mejillones Bay. The quantitative evidence from the multivariate analyses supports that the benthic microbial assemblages' features were linked to specific environments associated with Cu and Fe fractions, mainly in the Bay. Furthermore, the predicted functional microbial structure suggested that transporters and DNA repair allow the communities to respond to metals and endure the interacting variable environmental factors like dissolved oxygen, temperature, and salinity. Moreover, some active taxa recovered are associated with anthropogenic impact, potentially harboring antibiotic resistance and other threats in the coastal zone. Overall, the method of scoping eRNA in parallel with eDNA applied here has the capacity to significantly enhance the spatial and functional understanding of real-time microbial assemblages and, in turn, would have the potential to increase the acuity of biomonitoring programs key to responding to immediate management needs for the marine environment.

Jacaranda oil administration improves serum biomarkers and bioavailability of bioactive conjugated fatty acids, and alters fatty acid profile of mice tissues.

Jacaric acid, a conjugated linolenic acid (CLNA) present in jacaranda oil (JO), is considered a potent anticarcinogenic agent. Several studies have focused on its biological effects, but the metabolism once consumed is not clear yet. The aim of this work was to evaluate the effects of two different daily doses of JO on serum parameters and fatty acid (FA) profile of mice tissues after 4 weeks of feeding. No significant changes on body weight gain, food intake, or tissue weight were determined after 0.7 or 2 ml/kg of JO supplementation compared to control animals. Significantly lower blood low-density lipoproteins-cholesterol (20 mg/dl) and glucose (~147-148 mg/dl) levels were detected in both oil-treated groups compared to control (31.2 and 165 mg/dl, respectively). Moreover, jacaric acid was partially converted into cis9, trans11 conjugated linoleic acid (CLA) and thus further incorporated into tissues. Liver evidenced the highest total conjugated fatty acid content (1.1%-2.2%), followed by epididymal (0.7%-1.9%) and mesenteric (1.4%-1.8%) fat. Lower saturated and higher unsaturated fatty acid content was detected in both oil-treated groups compared to control. Our results support the safety of JO and its potential application with a functional or nutraceutical propose, by increasing human CLNA consumption and further availability of CLA.

Benthic microbial diversity trends in response to heavy metals in an oxygen-deficient eutrophic bay of the Humboldt current system offshore the Atacama Desert.

Mejillones Bay is a coastal ecosystem situated in an oxygen-deficient upwelling area impacted by mining activities in the coastal desert region of northern Chile, where conspicuous microbial life develops in the sediments. Herein, heavy metal (loid)s (HMs) such as Cu, Pb, As, Zn, Al, Fe, Cd, Mo, Ni and V as well as benthic microbial communities were studied using spectrometry and iTag-16 S rRNA sequencing. Samples were taken from two contrasting sedimentary localities in the Bay named Punta Rieles (PR) and Punta Chacaya (PC) within 10-50 m water-depth gradient. PR sediments were organic matter rich (21.1% of TOM at 50 m) and overlaid with low-oxygen waters (<0.06 ml O2/L bottom layer) compared with PC. In general, HMs like Al, Ni, Cd, As and Pb tended to increase in concentration with depth in PR, while the opposite pattern was observed in PC. In addition, PR presented a higher number of unique families (72) compared to PC (35). Among the top ten microbial families, Desulfobulbaceae (4.6% vs. 3.2%), Flavobacteriaceae (2.8% vs. 2.3%) and Anaerolineaceae (3.3% vs. 2.3%) dominated in PR, meanwhile Actinomarinales_Unclassified (8.1% vs. 4.2%) and Sandaracinaceae (4.4% vs. 2.0%) were more abundant in PC. Multivariate analyses confirmed that water depth-related variation was a good proxy for oxygen conditions and metal concentrations, explaining the structure of benthic microbial assemblages. Cd, Ni, As and Pb showed uniformly positive associations with communities that represented the keystone taxa in the co-occurrence network, including Anaerolineaceae, Thiotrichaceae, Desulfobulbaceae, Desulfarculaceae and Bacteroidales_unclassified communities. Collectively, these findings provide new insights for establishing the ecological interconnections of benthic microorganisms in response to metal contamination in a coastal upwelling environment.

Tissue tolerance to cyanoacrylate adhesives for closure of surgical wounds in Trachemys scripta skin.

BACKGROUND: The aim of this study was to evaluate the histological tolerance of medical cyanoacrylate adhesives (CAs), butyl-CA and octyl-CA, applied by two different methods in surgical skin incisions of T. scripta. METHODS: A two-trial controlled blind study each one including 12 female adult T. scripta turtles. Two 1-cm long full-thickness surgical skin incisions were made on the dorsal aspect of each hind limb. In trial 1 CAs were applied superficially over the apposed wound edges; each animal's four wounds were closed using butyl-CA, octyl-CA and ethyl-CA or absorbable suture as controls. In trial 2 adhesives were applied holding wound edges everted, and octyl-CA was replaced by a non-sutured control wound. At each time point (2, 7, 14 and 21 days) all wounds from three randomly chosen animals were biopsied. RESULTS: Medical grade CAs did not induce any sign of tissue damage and/or inflammatory reaction attributable to histotoxicity independently of the method of application. Wound dehiscence rate was higher when CAs were applied superficially over the apposed wound edges. CONCLUSIONS: Octyl and butyl-CA are well tolerated by turtles' soft skin but because of their high rate of dehiscence they are not recommended in high tension wounds; use in low tension wounds needs further investigation.

Greenhouse gases and biogeochemical diel fluctuations in a high-altitude wetland.

The landscapes of high-altitude wetland ecosystems are characterized by different kinds of aquatic sites, including ponds holding conspicuous microbial life. Here, we examined a representative pond of the wetland landscape for dynamics of greenhouse gases, and their association with other relevant biogeochemical conditions including diel shifts of microbial communities' structure and activity over two consecutive days. Satellite image analysis indicates that the area of ponds cover 238 of 381.3 Ha (i.e., 62.4%), representing a significant landscape in this wetland. Solar radiation, wind velocity and temperature varied daily and between the days sampled, influencing the biogeochemical dynamics in the pond, shifting the pond reservoir of inorganic versus dissolved organic nitrogen/phosphorus bioavailability, between day 1 and day 2. Day 2 was characterized by high dissolved organic nitrogen/phosphorus and N2O accumulation. CH4 presented a positive excess showing maxima at hours of high radiation during both days. The microbial community in the sediment was diverse and enriched in keystone active groups potentially related with GHG recycling including bacteria and archaea, such as Cyanobacteria, Verrucomicrobia, Rhodobacterales and Nanoarchaeaota (Woesearchaeia). Archaea account for the microbial community composition changes between both days and for the secondary productivity in the water measured during day 2. The results indicate that an intense recycling of organic matter occurs in the pond systems and that the activity of the microbial community is correlated with the availability of nutrients. Together, the above results indicate a net sink of CO2 and N2O, which has also been reported for other natural and artificial ponds. Overall, our two-day fluctuation study in a representative pond of a high-altitude wetland aquatic landscape indicates the need to explore in more detail the short-term besides the long-term biogeochemical variability in arid ecosystems of the Andes plateau, where wetlands are hotspots of life currently under high anthropogenic pressure.

Bacterioplankton response to nitrogen and dissolved organic matter produced from salmon mucus.

Aquaculture releases organic matter to the water column through excretion, fecal pellets, and uneaten food, but also by the continuous release of fish epithelium mucus. The effect of the latter on natural bacterial assemblages was determined using ammonium amended experiments at Puyuhuapi fjord in Chilean Patagonia. Mucus was added to seawater coming from 2 and 100 m depth and ammonium, nitrite and nitrate, dissolved organic carbon (DOC), picoplankton abundance, and active composition (i-tag 16S rRNA) were followed for 24 h. The results showed a significant response from the microbial community but only at surface depth after 2 and 6 h of incubation. A reduction of DOC and ammonium concentration and accumulation of nitrite and nitrate over time was observed, mainly at 100 m. Changes in the composition of active bacteria between treatments were observed at different taxonomic levels, associated with Alphaproteobacteria (Clade SAR11), Bacteroidetes (Polaribacter) and Gammaproteobacteria (Colwellia, Oceaniserpentilla) and other bacteria such as Nitrospina sp, a nitrite-oxidizing bacteria at some hours during the incubation. Fish pathogens, such as Vibrio and Piscirickettsia were rare (<0.02%). Overall, our study suggests that fish mucus can cause rapid modifications in microbial assemblages and stimulate organic matter and nutrient cycling, including heterotrophic and autotrophic (nitrification) in areas influenced by aquaculture.

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

Salar de Huasco is a wetland in the Andes mountains, located 3800 m above sea level at the Chilean Altiplano. Here we present a study aimed at characterizing the viral fraction and the microbial communities through metagenomic analysis. Two ponds (H0 and H3) were examined in November 2015. Water samples were processed using tangential flow filtration to obtain metagenomes from which the DNA fraction of the sample was amplified and sequenced (HiSeq system, Illumina). The ponds were characterized by freshwater and the viral-like particles to picoplankton ratio was 12.1 and 2.3 for H0 and H3, respectively. A great number of unassigned viral sequences were found in H0 (55.8%) and H3 (32.8%), followed by the family Fuselloviridae 20.8% (H0) and other less relatively abundant groups such as Microviridae (H0, 11.7% and H3, 3.3%) and Inoviridae (H3, 2.7%). The dominant viral sequences in both metagenomes belong to the order Caudovirales, with Siphoviridae being the most important family, especially in H3 (32.7%). The most important bacteria phyla were Proteobacteria, Bacteroidetes and Firmicutes in both sites, followed by Cyanobacteria (H0). Genes encoding lysogenic and lytic enzymes (i.e., recombinases and integrases) were found in H0 and H3, indicating a potential for active viral replication at the time of sampling; this was supported by the presence of viral metabolic auxiliary genes at both sites (e.g., cysteine hydrolase). In total, our study indicates a great novelty of viral groups, differences in taxonomic diversity and replication pathways between sites, which contribute to a better understanding of how viruses balance the cycling of energy and matter in this extreme environment.

Assessment of effects of methylene blue on intestinal ischemia and reperfusion in a rabbit model: hemodynamic, histological and immunohistochemical study.

BACKGROUND: Intestinal ischemia-reperfusion (IR) is an important clinical occurrence seen in common diseases, such as gastric dilatation-volvulus in dogs or colic in horses. Limited data is available on the use of methylene blue in veterinary medicine for intestinal ischemia-reperfusion. The present study aimed to compare the hemodynamic, histopathological, and immunohistochemical effects of two doses of methylene blue in two rabbit model groups In one group, 5 mg/kg IV was administered, and in another, 20 mg/kg IV was administered following a constant rate infusion (CRI) of 2 mg/kg/h that lasted 6 h. All the groups, including a control group had intestinal ischemia-reperfusion. Immunohistochemical analysis was performed using caspase-3. RESULTS: During ischemia, hemodynamic depression with reduced perfusion and elevated lactate were observed. During reperfusion, methylene blue (MB) infusion generated an increase in cardiac output due to a positive chronotropic effect, an elevation of preload, and an intense positive inotropic effect. The changes in heart rate and blood pressure were significantly greater in the group in which methylene blue 5 mg/kg IV was administered (MB5) than in the group in which methylene blue 20 mg/kg IV dose was administered (MB20). In addition, lactate and stroke volume variations were significantly reduced, and vascular resistance was significantly elevated in the MB5 group compared with the control group and MB20 group. The MB5 group showed a significant decrease in the intensity of histopathological lesion scores in the intestines and a decrease in caspase-3 areas, in comparison with other groups. CONCLUSIONS: MB infusion produced improvements in hemodynamic parameters in rabbits subjected to intestinal IR, with increased cardiac output and blood pressure. An MB dosage of 5 mg/kg IV administered at a CRI of 2 mg/kg/h exhibited the most protective effect against histopathological damage caused by intestinal ischemia-reperfusion. Further studies with MB in clinical veterinary pathologies are recommended to fully evaluate these findings.

Aquatic Thermal Reservoirs of Microbial Life in a Remote and Extreme High Andean Hydrothermal System.

Hydrothermal systems are ideal to understand how microbial communities cope with challenging conditions. Lirima, our study site, is a polyextreme, high-altitude, hydrothermal ecosystem located in the Chilean Andean highlands. Herein, we analyze the benthic communities of three nearby springs in a gradient of temperature (42-72 °C represented by stations P42, P53, and P72) and pH, and we characterize their microbial diversity by using bacteria 16S rRNA (V4) gene metabarcoding and 16S rRNA gene clone libraries (bacteria and archaea). Bacterial clone libraries of P42 and P53 springs showed that the community composition was mainly represented by phototrophic bacteria (Chlorobia, 3%, Cyanobacteria 3%, at P42; Chlorobia 5%, and Chloroflexi 5% at P53), Firmicutes (32% at P42 and 43% at P53) and Gammaproteobacteria (13% at P42 and 29% at P53). Furthermore, bacterial communities that were analyzed by 16S rRNA gene metabarcoding were characterized by an overall predominance of Chloroflexi in springs with lower temperatures (33% at P42), followed by Firmicutes in hotter springs (50% at P72). The archaeal diversity of P42 and P53 were represented by taxa belonging to Crenarchaeota, Diapherotrites, Nanoarchaeota, Hadesarchaeota, Thaumarchaeota, and Euryarchaeota. The microbial diversity of the Lirima hydrothermal system is represented by groups from deep branches of the tree of life, suggesting this ecosystem as a reservoir of primitive life and a key system to study the processes that shaped the evolution of the biosphere.

Greenhouse gas cycling by the plastisphere: The sleeper issue of plastic pollution.

Plastic is an allochthonous material to marine ecosystems but is rapidly colonized by marine microbial communities, with an as yet unclear contribution to biogeochemical cycles. In this study, we investigated the influence of an active microbial community grown on microplastic particles (the plastisphere) on CO2 and N2O recycling and its potential role in greenhouse gas inventories and air-sea exchange. Microplastics were collected during two cruises (Cimar 21 and FIP Montes Submarinos) from the surface layer (5 m depth) from several contrasting trophic regions of the South Pacific Ocean, i.e., from a transition zone off the eutrophic coastal upwelling of Chile, to a mesotrophic transition area of oceanic seamounts and, finally, to an oligotrophic zone in the South Pacific Subtropical Gyre. . Experiments were carried out onboard to evaluate CO2 and N2O production/consumption by the plastisphere. The active microbial community and its specific quantification were determined for Cimar 21 using iTag 16 S rRNA. The experiments showed that the plastisphere generally contributed to CO2 and N2O production/consumption, with rates ranging from -20.5 (consumption) to +4.5 (production) µmol/m2/d. The seamounts and the transition zone presented the highest production/consumption rates. The experiments performed in the two seamount stations showed that production and consumption of CO2 were related to the environmental nutrient concentration. Both stations presented N2O consumption that was associated with the high nitrogen deficit of the subantarctic water mass. The transition zone presented CO2 and N2O production in a plastisphere dominated by heterotrophic communities. The plastisphere in oligotrophic waters was diverse and active. The experiments, however, presented low or no production of greenhouse gases. Our results show a contribution of CO2 and N2O to the global gas surface inventories and air-sea exchange is lower than 1% of the global sources. These results highlight different critical impacts of plastic pollution on the environment that have, until now, not been considered.

Adaptive Strategies in a Poly-Extreme Environment: Differentiation of Vegetative Cells in Serratia ureilytica and Resistance to Extreme Conditions.

Poly-extreme terrestrial habitats are often used as analogs to extra-terrestrial environments. Understanding the adaptive strategies allowing bacteria to thrive and survive under these conditions could help in our quest for extra-terrestrial planets suitable for life and understanding how life evolved in the harsh early earth conditions. A prime example of such a survival strategy is the modification of vegetative cells into resistant resting structures. These differentiated cells are often observed in response to harsh environmental conditions. The environmental strain (strain Lr5/4) belonging to Serratia ureilytica was isolated from a geothermal spring in Lirima, Atacama Desert, Chile. The Atacama Desert is the driest habitat on Earth and furthermore, due to its high altitude, it is exposed to an increased amount of UV radiation. The geothermal spring from which the strain was isolated is oligotrophic and the temperature of 54°C exceeds mesophilic conditions (15 to 45°C). Although the vegetative cells were tolerant to various environmental insults (desiccation, extreme pH, glycerol), a modified cell type was formed in response to nutrient deprivation, UV radiation and thermal shock. Scanning (SEM) and Transmission Electron Microscopy (TEM) analyses of vegetative cells and the modified cell structures were performed. In SEM, a change toward a circular shape with reduced size was observed. These circular cells possessed what appears as extra coating layers under TEM. The resistance of the modified cells was also investigated, they were resistant to wet heat, UV radiation and desiccation, while vegetative cells did not withstand any of those conditions. A phylogenomic analysis was undertaken to investigate the presence of known genes involved in dormancy in other bacterial clades. Genes related to spore-formation in Myxococcus and Firmicutes were found in S. ureilytica Lr5/4 genome; however, these genes were not enough for a full sporulation pathway that resembles either group. Although, the molecular pathway of cell differentiation in S. ureilytica Lr5/4 is not fully defined, the identified genes may contribute to the modified phenotype in the Serratia genus. Here, we show that a modified cell structure can occur as a response to extremity in a species that was previously not known to deploy this strategy. This strategy may be widely spread in bacteria, but only expressed under poly-extreme environmental conditions.

Active microbiome structure and its association with environmental factors and viruses at different aquatic sites of a high-altitude wetland.

Salar de Huasco is a high-altitude wetland characterized by a highly diverse microbial life adapted to extreme climatic and environmental conditions. Our study aims to determine active microbial community structure changes within different aquatic sites and its relationship with environmental factors and viruses as potential drivers of diversification in different aquatic areas of this ecosystem. In this study, bacteria and archaea composition (16S rRNA subunit pyrolibraries) and picoplankton and viral abundance were determined at ponds, springs and lagoon sites of the wetland during wet and dry seasons (February and July 2012, respectively). In general, mixosaline waters (1,400-51,000 µS/cm) usually found in ponds and lagoon presented higher picoplanktonic abundances compared to freshwater (<800 µS/cm) spring sites, ranging from 1.07 × 105 to 1.83 × 107  cells/ml. Viral abundance and viral to picoplankton ratio (VPR) also presented greater values at ponds compared to spring sites, reaching up to 4.78 × 108 viruses-like particles and up to 351 for VPR. In general, ponds hold a higher microbial diversity and complexity associated also with the presence of microbial mats compared with water sources or lagoon (Shannon index H' 2.6-3.9 vs. <2.0). A greater richness of archaea was also detected in ponds characterized by functional groups such as known methanogens and ammonia oxidizers, and uncultured groups. In total, our results indicate that among the different aquatic sites of the wetland, ponds presented a great microbial community diversification associated to a higher top-down control by viruses which may influence nutrient and greenhouse gases cycling.