Spatio-Temporal Variations in the Abundance and Structure of Denitrifier Communities in Sediments Differing in Nitrate Content.

Spatial and temporal variations related to hydric seasonality in abundance and diversity of denitrifier communities were examined in sediments taken from two sites differing in nitrate concentration along a stream Doñana National Park during a 3-year study. We found a positive relationship between the relative abundance of denitrifiers, determined as , , , and denitrification genes, and sediment nitrate content, with similar spatial and seasonal variations. However, we did not find association between denitrification activity and the community structure of denitrifiers. Because showed the strongest correlation with the content of nitrate in sediments, we used this gene as a molecular marker to construct eight genomic libraries. Analysis of these genomic libraries revealed that diversity of the -bearing communities was higher in the site with higher nitrate content. Regardless of nitrate concentration in the sediments, the Bradyrhizobiaceae and Rhodocyclaceae were the most abundant families. On the contrary, Rhizobiaceae was exclusively present in sediments with higher nitrate content. Results showed that differences in sediment nitrate concentration affect the composition and diversityof -bearing communities.