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Marine Ecology Progress Series

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MEPS 448:79-92 (2012)  -  DOI:

Denitrification: an ecosystem service provided by salt marshes

Ana I. Sousa1,2,*, Ana I. Lillebø2, Nils Risgaard-Petersen3, Miguel A. Pardal4, Isabel Caçador1

1Centre of Oceanography (CO), Faculty of Sciences, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal
2Department of Biology & CESAM, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
3Institute of Biological Science, Center for Geomicrobiology, Aarhus University, Ny Munkegade, Building 1540,
8000 Aarhus C, Denmark
4Centre for Functional Ecology (CFE), Department of Life Sciences, University of Coimbra, Apartado 3046,
3001-401 Coimbra, Portugal

ABSTRACT: We hypothesized that denitrification rates, as an N removal process, would be enhanced in salt marsh rhizosediments as compared to sediments without vegetation (bare mudflats). Denitrification rates (measured by the 15N-isotope pairing technique), potential nitrification, and nutrient fluxes were seasonally quantified in a Spartina maritima salt marsh and in adjacent bare mudflats. Potential nitrification rates were significantly higher in autumn and winter, but there were no significant differences between the bare mudflats and S. maritima vegetated sediment. Seasonally, denitrification rates in vegetated sediments under dark conditions were significantly higher in winter (676 ± 497 µmol N2 m−2 h−1, mean ± SD), whereas bare mudflats showed a maximum rate of 151 ± 24 µmol N2 m−2 h−1 in summer. The high denitrification rates recorded in winter may be due to many abiotic and biotic factors, namely higher potential nitrification and nitrate availability in the water column, lower competition for nitrogen within the sediment, and less competition between plants, microphytobenthos, and nitrifiers, especially in dark conditions. Hence, during winter, there was a higher contribution of S. maritima marshes to N removal through denitrification, highlighting the role of the marshes in this ecosystem service. As a whole, considering the seasonal variations of the studied processes, it cannot be concluded whether or not annual denitrification was significantly different between the vegetated sediment and the bare mudflats.

KEY WORDS: Denitrification · Salt marshes · Ecosystem services · Eutrophication · Spartina maritima · 15N-isotope pairing technique

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Cite this article as: Sousa AI, Lillebø AI, Risgaard-Petersen N, Pardal MA, Caçador I (2012) Denitrification: an ecosystem service provided by salt marshes. Mar Ecol Prog Ser 448:79-92.

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