Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano

Abstract

In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, 3H-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 μE m-2 s-1, 72 W m-2 and 12 W m-2 were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by 3H-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco.

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

“…Spring sites were characterized by fresh and high nitrate and low phosphate concentration, compared with the other areas. These characteristics were found to be consistent with our previous data, using similar analytical methods at the spring site H0 (Hernández et al., ; Molina et al., ). On the other hand, ponds areas were mixosaline and with variable nutrients concentration.…”

“…Indeed, a high benthic primary production has been reported at the lagoon of Salar de Huasco (de la Fuente, ). Moreover, a high microbial activity based on 3 H‐leucine incorporation was determined at ponds in the same study area, from a later sampling carried out at November 2014 (dry season), showing also a significant correlation between the microbial activity and phosphate and conductivity (Hernández et al., ). Moreover, during our study, the ponds and the lagoon at the wetland characterized by oligosaline and close to mesosaline conditions hold an abundant picoplankton community compared with spring sites (Figure ), indicating a higher microbial activity at these sites.…”

“…Samples for picoplankton and viral abundance and for RNA sequencing were taken in 5 (February) and 4 (July) aquatic sites (Figure ) with different conductivity, including; springs, characterized usually by low conductivity associated with freshwater from groundwater origin; the main lagoon or lake with mixosaline and sometimes hypersaline water and small ponds presenting a wide range of conductivity associated with mixosaline conditions, sometimes having microbial mats (Figures S1 and S2). Depending on their water source, ponds could be transient and disappear associated with desiccation (Hernández et al., ). In our case, we only visit the pond at H4 during both dates (Table S1).…”

“…These latter water presents a chemical composition that consists in sulfate, chloride, calcium, sodium, potassium, and magnesium in different proportions than seawater (Risacher et al., ). The diverse and heterogeneous aquatic environments (springs, several ponds, and a main lagoon) of the wetland also present variable biogeochemical conditions including nutrients and dissolved organic matter (Aguilar, Acosta, Dorador, & Sommaruga, ; Dorador et al., ; Hernández et al., ). In total, the environmental high‐altitude wetland conditions were consider as drivers of diversification, generating ecological niches for plankton, benthos, microbial mats, and microbialites (Albarracín et al., ), which represent a higher degree of microbial complexity.…”

Spectral model for long‐term computation of thermodynamics and potential evaporation in shallow wetlands

“…These systems are hydrologically closed, as the water that precipitates in the basin is completely evaporated from the terminal shallow wetland, thus evapoconcentrating the salts and reaching values as high as 150 g L −1 , which is why these shallow wetlands are named Salars [ Dorador et al ., ; de la Fuente and Niño , ]. The desert climate and high altitude of these systems (higher than 3000 m above sea level) impose extreme environmental conditions on the ecosystems, such as low oxygen in the atmosphere, high levels of ultraviolet radiation, high daily temperature ranges, and hypersaline waters [ de la Fuente , ; Hernández et al ., ], thus resembling many aspects of the environment in which life originally developed on Earth [ Belluscio , ]. Furthermore, the water temperature varies by 20–30°C in a day [ de la Fuente and Niño , ; de la Fuente , ].…”