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MEPS 670:15-31 (2021)  -  DOI:

Benthic oxygen fluxes in a coastal upwelling system (Ria de Vigo, NW Iberia) measured by aquatic eddy covariance

M. Amo-Seco1,2,*, C. G. Castro1, N. Villacieros-Robineau1, F. Alonso-Pérez1,5, R. Graña3, G. Rosón4, P. Berg2

1Instituto de Investigacións Mariñas (IIM), CSIC, Vigo 36208, Spain
2Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA
3Centro Oceanográfico de Gijón, IEO, Gijón 33212, Spain
4Departamento de Física Aplicada, Universidade de Vigo, Vigo 36310, Spain
5Present address: Centro Oceanográfico de Vigo, IEO, Vigo 36390, Spain
*Corresponding author:

ABSTRACT: Organic carbon mineralization and nutrient cycling in benthic environments are critically important for their biogeochemical functioning, but are poorly understood in coastal upwelling systems. The main objective of this study was to determine benthic oxygen fluxes in a muddy sediment in the Ria de Vigo (NW Iberian coastal upwelling), by applying the aquatic eddy covariance (AEC) technique during 2 campaigns in different seasons (June and October 2017). The main drivers of benthic fluxes were studied and compared among days in each season and between seasons. The 2 campaigns were characterized by an upwelling-relaxation period followed by a downwelling event, the last of which was due to the extratropical cyclone Ophelia in October. The mean (±SD) seasonal benthic oxygen fluxes were not significantly different for the 2 campaigns despite differences in hydrodynamic and biogeochemical conditions (June: -20.9 ± 7.1 mmol m-2 d-1 vs. October: -26.5 ± 3.1 mmol m-2 d-1). Benthic fluxes were controlled by different drivers depending on the season. June was characterized by sinking labile organic material, which enhanced benthic fluxes in the downwelling event, whereas October had a significantly higher bottom velocity that stimulated the benthic fluxes. Finally, a comparison with a large benthic chamber (0.50 m2) was made during October. Despite methodological differences between AEC and chamber measurements, concurrent fluxes agreed within an acceptable margin (AEC:benthic chamber ratio = 0.78 ± 0.13; mean ± SD). Bottle incubations of water sampled from the chamber interior indicated that mineralization could explain this difference. These results show the importance of using non-invasive techniques such as AEC to resolve benthic flux dynamics.

KEY WORDS: Benthic fluxes · Aquatic eddy covariance · Benthic chamber · Dissolved oxygen · Muddy sediments · Upwelling system · Rias

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Cite this article as: Amo-Seco M, Castro CG, Villacieros-Robineau N, Alonso-Pérez F, Graña R, Rosón G, Berg P (2021) Benthic oxygen fluxes in a coastal upwelling system (Ria de Vigo, NW Iberia) measured by aquatic eddy covariance. Mar Ecol Prog Ser 670:15-31.

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