TITLE:
Geothermal Diatoms: Seasonal Variability in the El Tatio Geothermal Field (Altiplano, Chile)
AUTHORS:
Alejandro Angel, Irma Vila, Carolina Díaz, Ximena Molina, Paola Sepúlveda
KEYWORDS:
Canonical Correspondence Analysis, Cluster, Conductivity, Fumaroles, Size Fraction
JOURNAL NAME:
Advances in Microbiology,
Vol.8 No.3,
March
30,
2018
ABSTRACT: Diatom floras were examined in a high-altitude geothermal field, 4200 - 4500 m (29°19'S 68°W'), located in the Central Andean dry Puna ecoregion or southern Altiplano. These locations include hostile environments subjecting living organisms to extreme conditions. The aim of the present study was to investigate the spatial patterns and describe the response of diatom assemblages to differences in physical and chemical variables. Different shallow (Achnanthidium exiguum (Grunow) Czarnecki, Cocconeis placentula var. lineata (Ehrenberg) Van Heurck, Eolimna minima (Grunow) Lange-Bertalot, Staurosirella pinnata (Ehrenberg) Williams and Round, Navicula gregaria Donkin, Nitzschia inconspicua Grunow, Nitzschia palea (Kützing) Smith, Nitzschia perminuta (Grunow) Peragallo, and Planothidium lanceolatum (Brébisson ex Kützing) Lange-Bertalot. As expected, the 20 to 200 μm-size fraction contained the highest numbers of diatom taxa (53 species), although an unexpectedly high number (47 species) were also found in the smaller 5 to 20 μm-size fraction, more associated to fumaroles and saline systems. The 180 to 2000 μm size fraction contained only two species, including rosette-forming diatom Ulnaria ulna (Nitzsch) Compère, and the unicellular species Surirella chilensis Janisch, both species exclusively reported in freshwater systems. Canonical correspondence analysis (CCA) and Monte Carlo permutation tests showed clear correlations between species, conductivity, TP (total phosphorous), NO3- , HO3- , Mg2+, temperature and dissolved oxygen (DO). The gradient of ionic composition values explaining most variation in diatom assemblages ranged from waters dominated by Ca2+ and SO4- to waters with higher proportions of Na+, K+, F-, Li+, Mg2+ and Cl-. Other factors include substrate type, presence of macrophytes, current velocity and other local environmental conditions. The results presented here enhance our understanding of diatom richness/composition in hostile environments from a high-altitude arid and semi-arid geothermal region.