Rev. biol. mar. oceanogr. 50(1): 95-110

Article

Structure of denitrifying communities reducing N₂O at suboxic waters off northern Chile and Perú

Maribeb Castro-González¹, Osvaldo Ulloa² and Laura Farías³

¹Laboratorio de Ecología Microbiana, Departamento de Biología, Universidad del Tolima, Código Postal 730006299, Ibagué, Colombia

²Departamento de Oceanografia e Instituto Milenio de Oceanografia, Universidad de Concepción, Casilla 160-C, Concepción, Chile

³Departamento de Oceanografía, Universidad de Concepción, Centro de Ciencia del Clima y la Resiliencia (CR)2, Casilla 160-C, Concepción, Chile

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The nosZ gene, which encodes for N₂O reduction to N₂, was used to study the structure of denitrifying communities in the oxygen minimum zone off Chilean and Peruvian coast throughout terminal restriction fragment length polymorphism (TRFLP) and cloning of nosZ genes. TRFLP analysis showed little diversity of nosZ genes at suboxic depths (Oxygen Minimum Zone´s core) compared with depths where O₂ largely varied (upper limit of OMZ or ULOMZ). The nosZ-denitrifying communities showed differences in its structure between geographical locations and time sampling suggesting an association with the shift in the environmental conditions. The canonical correspondence analysis showed that the environmental parameters selected as predictor variables (N₂O, O₂, NH₄⁺ and NO₂^-) explained well the differences in nosZ-denitrifying community composition among sampling sites. The phylogenetic analysis showed little nosZ sequence diversity and grouped 81% of nosZ-clones near the cluster of sediments sequences from Pacific. Our sequences did not branch with any known denitrifying bacteria or seawater nosZ-sequences available, demonstrating the novelty of phylotypes founded in this area.

Key words:  Eastern South Pacific, nosZ gene, Oxygen Minimum Zone