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AME prepress abstract   -  DOI:

Spatial-temporal dynamics of N-cycle functional genes in a temperate Atlantic estuary (Douro, Portugal)

P. Salgado*, A. Machado, A. A. Bordalo

*Corresponding author:

ABSTRACT: Understanding the spatial and seasonal dynamics of nitrogen (N) – cycle microbial communities is pivotal for the knowledge of the N biogeochemistry. This research dealt with the spatial-temporal variability of nitrification (bacterial and archaeal amoA) and denitrification (nirS, nirK and nosZI) key genes, as well as of non-denitrifying nitrous oxide (N2O) reducers (nosZII), coupled with key environmental variables, in an estuarine ecosystem (Douro, NW Portugal). Samples were collected on a monthly basis over one year, key physical-chemical parameters measured, and specific functional genes abundance assayed. The results revealed a clear seasonality for nirS, nosZII, bacterial and archaeal amoA abundance, with an increase during the winter/spring seasons. This period was especially characterized by high levels of dissolved oxygen, low temperature, low salinity, and increased turbidity. Indeed, turbidity emerged as the key factor controlling the distribution of nirS, nosZII bacterial, and archaeal amoA abundance. In contrast, the abundance of nosZI increased during the summer, while the nirK abundance was enhanced from the fall to late spring. Additionally, the availability of nitrogen dissolved nutrients had no commensurable effect on N-cycle functional genes. This study covers the annual variation of N-cycle functional genes in a temperate Atlantic estuary and provides a major contribution for the understanding on how environmental factors potentially influence the distribution and abundance of N-cycle microbial communities.