Gases invernadero en el embalse de Prado, Tolima 399 Rev. Acad. Colomb. Cienc. Ex. Fis. Nat. 39(152):399-407, julio-septiembre de 2015 Gases invernadero en aguas con bajo oxígeno en el reservorio eutrófico de Prado (Colombia) Maribeb Castro-González*, Victoria Torres-Valdés Laboratorio de Ecología Microbiana, Facultad de Ciencias, Universidad del Tolima, Ibagué, Colombia ResumenEn esta investigación se cuantificó la concentración de gases invernadero (metano y óxido nitroso) y de otros parámetros fisicoquímicos en la columna de agua del reservorio eutrófico de Prado para determinar con experimentos in situ el origen del óxido nitroso y la distribución vertical de ambos gases. Los resultados indicaron que la nitrificación contribuyó más activamente que la desnitrificación a la producción de óxido nitroso en la columna de agua, con tasas estimadas en 122,5 ± 79,9 nM/d, y que comparado con otras hidroeléctricas y lagos en el mundo, las concentraciones de óxido nitroso (de hasta 38,6 ± 0,9 nM) y de metano (de hasta 242 ± 85,5 µM) cuantificadas en el embalse fueron altas. Este es el primer estudio desarrollado en la represa de Prado que muestra la sobresaturación de ambos gases en la columna de agua, lo que sugiere que esta hidroeléctrica podría estar emitiendo cantidades significativas de gases invernadero a la atmósfera.Palabras clave: hidroeléctrica, embalse tropical, óxido nitroso, metano, nitrificación, desnitrificación. Greenhouse gases in low-oxygen waters in the eutrophic reservoir of Prado (Colombia) AbstractIn this study we quantified greenhouse gases concentration (nitrous oxide and methane) and other physicochemical parameters in the water column of Prado eutrophic reservoir to determine with in situ experiments the nitrous oxide source and the vertical distribution of both gases. The results indicated that nitrification contributed more actively than denitrification to nitrous oxide production in the water column to estimated rates of 122.5 ± 79.9 nM/d, and that, in comparison with other dams and lakes in the world, the nitrous oxide (up to 38.6 ± 0.9 nM) and methane concentrations (up to 242 ± 85.5 µM) measured in the reservoir were high. This is the first study in the Prado dam showing the oversaturation of both gases in the water column, which suggests that this reservoir could be emitting significant quantities of greenhouse gases to the atmosphere.

Urban wetlands are biodiversity reservoirs sustained by microbe-mediated processes. In tropical zones, wetland microbial dynamics remain poorly understood. Chemical parameters, heavy metal content, and microbiological community structure were investigated in surface sediments of the Santa Maria del Lago (SML) wetland in Bogota, Colombia. High-throughput sequencing was employed to generate RNAr 16S and nosZ gene sequence data with which bacteria, archaea, and nosZ-type denitrifier community composition and their phylogenetic relationships were investigated. A canonical correspondence analysis was conducted to determine the relationship between assessed environmental variables and microbial community composition. Results showed that the most abundant bacterial phyla were Proteobacteria, Acidobacteria (group GP18), and Aminicenantes; Archaea were represented by the taxa Methanomicrobia and Thermoprotei, and the nosZ community was dominated by Candidatus Competibacter denitrificans. A phylogenetic analysis revealed a high diversity of Operational Taxonomic Units (OTUs), according to 16S rRNA gene sequence data; however, the quantity and diversity of OTUs from the nosZ community were low compared to previous studies. High concentrations of ammonium, phosphorus, organic carbon, Pb, Fe, Zn, Cu, and Cd, were detected in sediments, but they were not strongly related to observed microbial community compositions. In conclusion, in the same polluted SML wetland sediments diverse bacteria and archaea communities were detected, although not nosZ-type denitrifiers.

Denitrification is a process of reduction of nitrate to dinitrogen by facultative anaerobic microorganisms, which have functional genes encoding denitrification enzymes (reductases). The nosZ gene encoding the enzyme that reduces nitrous oxide to dinitrogen was utilized in this research, as molecular marker for denitrifying communities into low oxygen waters of Prado reservoir. Our objective was to analyze and compare the composition (richness and abundance) of nosZ-type denitrifiers in relationship with physicochemical variables (oxygen, pH, temperature, nitrate, nitrite and ammonium) in three areas of this dam: Isla del Sol, Lozanía and Tomogó which are distant and have different anthropogenic influences. For this, we performed DNA extraction, amplification, 454 pyrosequencing and phylogenetic analysis of nosZ gene. The Chao1 estimator and Shannon index were used for compare richness and diversity of nosZ gene; and the relationship between compositions of operational taxonomic units (OTU) with physicochemical variables was established by canonical correspondence analysis (CCA). In the reservoir 45 nosZ-OTUs to species level (80% similarity) were detected. Lozanía had the highest number of OTUs (25) and greatest diversity (S CHAO1 : 35; H: 2.0), compared to the other areas sampling. The phylogenetic analysis showed the presence of many OTUs (28 of 45) with low similarity to Proteobacteria group and high similarity with sequences of environmental clones reported previously. The CCA showed that the nosZ-community composition of Prado dam was related with low pH (6.2), oxygen (0.01mg / L) and nitrate (<0.25 mg / L) recorded in the water column.