Benthic Oxygen Fluxes in a coastal upwelling system (Ría de Vigo, NW Iberia) measured with the Aquatic Eddy Covariance technique

Mariña Amo Seco1, Carmen G Castro1, Nicolas Villacieros-Robineau1, Fernando Alonso-Perez1, Rocío Graña2, Rosa Bañuelos1, Gabriel Roson3 and Peter Berg4, (1)Instituto de Investigación Mariñas - CSIC, Departamento de Oceanografía, Vigo, Spain, (2)Spanish Institute of Oceanography-CSIC, Gijón, Spain, (3)University of Vigo, Vigo, Spain, (4)University of Virginia, Department of Environmental Sciences, Charlottesville, VA, United States
Abstract:
Coastal regions support a high primary production acting as important parts of the global carbon and nutrients cycles. Main process like remineralization of the organic carbon and nutrients recycling take place in the bottom boundary layer, and these processes support the high coastal primary production. The benthic oxygen flux is widely used as a proxy for organic carbon remineralization. In the context of global warming and coastal eutrophication, the measurement of benthic oxygen flux is becoming a critical indicator of the good environmental status of marine coastal ecosystems.

The main objective of this study was to determine the benthic oxygen fluxes in two different seasonal campaigns (June and October 2017) in a muddy sediment site in the Ría de Vigo (NW Iberian Peninsula coastal upwelling system) applying a non-invasive technique, the Aquatic Eddy Covariance (AEC). A comparison between the AEC fluxes and the benthic chamber fluxes was made to implement this technique. Additionally, we identified which were the main forcing factors of benthic fluxes for the two seasons.

The mean benthic oxygen flux measured by AEC was (mean ± SD) -24.2±6.3 mmol O2·m-2·d-1 with a good agreement between both techniques (flux ratio of AEC: benthic chamber of 0.8). In both campaigns, we can distinguish a first period characterized by an upwelling event and a second period covering a downwelling event. Although seasonal mean benthic fluxes were not significantly different, diverse forcing factors modulated benthic fluxes in each season. While in June, the benthic oxygen fluxes were significantly higher during the downwelling event and the supply of organic matter controlled benthic O2 fluxes, in October they did not show significant differences between both periods, being the bottom velocity the main forcing factor.

Key words: Benthic Fluxes, Aquatic Eddy Covariance, Benthic Chamber, Coastal Upwelling.

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