Out of the blue: the independent activity of sulfur-oxidizers and diatoms mediate the sudden color shift of a tropical river oleh Alejandro Arce-Rodríguez, Eduardo Libby, Erick Castellón, Roberto Avendaño, Juan Carlos Cambronero, Maribel Vargas, Dietmar H. Pieper, Stefan Bertilsson, Max Chavarría, Fernando Puente-Sánchez