Publication Date:
2017-03-07
Description:
The upwelling system off central Chile (36.5°ree: S) is seasonally subjected to oxygen (O2) deficient waters, with a strong vertical gradient in O2 varying from oxic to anoxic conditions on a scale of a few meters (30–50 m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g., anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N-loss and its speciation, in the form of N2 and N2O, were studied using 15N-tracer incubations, inhibitor assays, the natural abundance of nitrate isotopes, and hydrographic information. Incubations were developed using water retrieved from the oxycline (25 m depth) and bottom waters (85 m depth), over the continental shelf off Concepción, Chile. Results of 15N-labeled incubations revealed a higher N removal activity during the austral summer, with denitrification as the dominant N2 producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline. Notwithstanding, a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40 μmol L−1), relative to the hypoxic bottom waters (
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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