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Forskningsartikel2023Vetenskapligt granskadÖppen tillgång

Out of the blue: the independent activity of sulfur-oxidizers and diatoms mediate the sudden color shift of a tropical river

Arce-Rodriguez, Alejandro; Libby, Eduardo; Castellon, Erick; Avendano, Roberto; Cambronero, Juan Carlos; Vargas, Maribel; Pieper, Dietmar H.; Bertilsson, Stefan; Chavarria, Max; Puente-Sanchez, Fernando


BackgroundRio Celeste ("Sky-Blue River") is a river located in the Tenorio National Park (Costa Rica) that has become an important hotspot for eco-tourism due to its striking sky-blue color. A previous study indicated that this color is not caused by dissolved chemical species, but by formation of light-scattering aluminosilicate particles at the mixing point of two colorless streams, the acidic Quebrada Agria and the neutral Rio Buenavista.ResultsWe now present microbiological information on Rio Celeste and its two tributaries, as well as a more detailed characterization of the particles that occur at the mixing point. Our results overturn the previous belief that the light scattering particles are formed by the aggregation of smaller particles coming from Rio Buenavista, and rather point to chemical formation of hydroxyaluminosilicate colloids when Quebrada Agria is partially neutralized by Rio Buenavista, which also contributes silica to the reaction. The process is mediated by the activities of different microorganisms in both streams. In Quebrada Agria, sulfur-oxidizing bacteria generate an acidic environment, which in turn cause dissolution and mobilization of aluminum and other metals. In Rio Buenavista, the growth of diatoms transforms dissolved silicon into colloidal biogenic forms which may facilitate particle precipitation.ConclusionsWe show how the sky-blue color of Rio Celeste arises from the tight interaction between chemical and biological processes, in what constitutes a textbook example of emergent behavior in environmental microbiology.


Geobiology; Hydroxyaluminosilicates; Hydrothermal; Sulfur oxidizing bacteria; Diatoms; Rio Celeste

Publicerad i

Environmental Microbiome
2023, Volym: 18, nummer: 1, artikelnummer: 6
Utgivare: BMC