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Marine Ecology Progress Series

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MEPS 390:79-95 (2009)  -  DOI:

Benthic nutrient recycling on the northeastern shelf of the Gulf of Cádiz (SW Iberian Peninsula)

S. Ferrón1,4,*, F. Alonso-Pérez2, E. Anfuso1, F. J. Murillo3, T. Ortega1, C. G. Castro2, J. M. Forja1

1Departamento de Química Física, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Campus Río San Pedro, s/n,11510 Puerto Real, Cádiz, Spain
2Departamento de Oceanografía, Instituto de Investigaciones Marinas, CSIC, c/ Eduardo Cabello 6, 36208 Vigo, Pontevedra, Spain
3Departamento de Zooloxía e Antropoloxía Física, Facultade de Bioloxía, Universidade de Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, A Coruña, Spain
4Present address: Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, Hawaii 96822, USA

ABSTRACT: Benthic fluxes of nutrients and dissolved nitrous oxide (N2O) were determined by benthic chamber incubations in 2 regions on the northeastern near-shore continental shelf of the Gulf of Cádiz (depth range: 8 to 34 m), one off the Guadalquivir River mouth and the other in the Bay of Cádiz and its neighboring shelf. In total, 25 in situ benthic chamber incubations were performed during June 2006, November 2006, and February 2007 to investigate the main factors controlling benthic nutrient recycling and its significance at the study site. Nutrient benthic fluxes (in m–2 d–1) varied between –0.9 and 1.0 mmol NO3, –0.3 and 0.3 mmol NO2, –1.2 and 3.5 mmol NH4+, –0.04 and 0.22 mmol HPO42–, and 0.2 and 2.9 mmol Si(OH)4. Benthic fluxes of N2O, ranging from –1.2 to 10.4 µmol N-N2O m–2 d–1, accounted on average for <1% of total inorganic nitrogen fluxes. The regeneration of NH4+ and Si(OH)4 was mainly influenced by organic carbon oxidation rates and bulk organic carbon in surface sediments, whereas HPO42– regeneration was mostly influenced by bottom water oxygen concentration and water depth. Denitrification was estimated to account for between 9 and 13% of organic matter remineralization and for a loss of between 57 and 67% of potentially recyclable nitrogen. Overall, benthic remineralization was estimated to degrade about 47% of overlying primary production, supplying about 15 and 12% of the phytoplankton N and P requirements, respectively. This highlights the importance of benthic organic matter remineralization on the biogeochemistry of the northeastern continental shelf of the Gulf of Cádiz.

KEY WORDS: Benthic fluxes · Nutrient regeneration · Denitrification · Nitrous oxide · Macrofauna · Coastal sediments · Gulf of Cádiz

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Cite this article as: Ferrón S, Alonso-Pérez F, Anfuso E, Murillo FJ, Ortega T, Castro CG, Forja JM (2009) Benthic nutrient recycling on the northeastern shelf of the Gulf of Cádiz (SW Iberian Peninsula). Mar Ecol Prog Ser 390:79-95.

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