title: 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-2s-1, 72 W m-2and 12 W m-2were 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 by3H-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.
authors.affiliation: Centro de Investigación Marina Quintay CIMARQ, Facultad de Ecología y Recursos Naturales, Universidad Andres BelloSantiago, Chile; Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de ChileValdivia, Chile.
authors.forename: Klaudia L
authors.initials: KL
authors.lastname: Hernández
authors.affiliation: Centro de Estudios Avanzados en Zonas AridasLa Serena, Chile; Facultad de Ciencias del Mar, Universidad Católica del NorteCoquimbo, Chile; Ecology and Sustainable Management of Oceanic Islands, Universidad Católica del Norte, CoquimboCoquimbo, Chile; Centro Universitario de la Región Este, Universidad de la RepúblicaRocha, Uruguay.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Yannicelli
authors.affiliation: Norwegian Polar Institute Tromsø, Norway.
authors.forename: Lasse M
authors.initials: LM
authors.lastname: Olsen
authors.affiliation: Laboratorio de Complejidad Microbiana y Ecología Funcional and Departamento de Biotecnología, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de AntofagastaAntofagasta, Chile; Centro de Biotecnología y BioingenieríaSantiago, Chile.
authors.forename: Cristina
authors.initials: C
authors.lastname: Dorador
authors.affiliation: Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de ChileValdivia, Chile; Programa de Postgrado en Oceanografía, Departamento de Oceanografía, Universidad de ConcepciónConcepción, Chile; Centro de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (FONDAP-IDEAL), Universidad Austral de ChileValdivia-Punta Arenas, Chile.
authors.forename: Eduardo J
authors.initials: EJ
authors.lastname: Menschel
authors.affiliation: Departamento de Biología, Observatorio de Ecología Microbiana, Facultad de Ciencias Naturales y Exactas, Universidad de Playa Ancha Valparaíso, Chile.
authors.forename: Verónica
authors.initials: V
authors.lastname: Molina
authors.affiliation: Laboratorio de Microbiología Aplicada y Extremófilos, Departamento de Ingeniería Química, Universidad Católica del Norte Antofagasta, Chile.
authors.forename: Francisco
authors.initials: F
authors.lastname: Remonsellez
authors.affiliation: Centro de Biotecnología y BioingenieríaSantiago, Chile; Departamento de Ciencias Farmacéuticas, Facultad de Ciencias, Universidad Católica del NorteAntofagasta, Chile.
authors.forename: Martha B
authors.initials: MB
authors.lastname: Hengst
authors.affiliation: Center for Environmental Diagnostics and Bioremediation, University of West Florida, Pensacola FL, USA.
authors.forename: Wade H
authors.initials: WH
authors.lastname: Jeffrey
keywords: Central Andes; Salar de Huasco; bacterial secondary production; environmental gradients; extremophiles; heterogeneous microbial production; light history; solar radiation