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Marine Ecology Progress Series

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MEPS 493:9-21 (2013)  -  DOI:

N2 fluxes in sediments of the Elbe Estuary and adjacent coastal zones

Astrid Deek1,2,*, Kirstin Dähnke1,*,**, Justus van Beusekom1, Sven Meyer3, Maren Voss3, Kay Emeis1,2

1Helmholtz Zentrum Geesthacht, Institute of Coastal Research, 21502 Geesthacht, Germany
2IfBM, University of Hamburg, 20146 Hamburg, Germany
3Baltic Sea Research Institute, 18119 Rostock, Germany
*These authors contributed equally**Corresponding author. Email:

ABSTRACT: The conversion of reactive nitrogen species to N2 during denitrification in sediments may be one of the most valuable ecosystem services provided by estuarine and intertidal environments near river discharge areas. To quantify the rates and limiting factors of denitrification in the estuary of the Elbe River and adjacent Wadden Sea (SE North Sea), we measured sediment N2 fluxes across subtidal and intertidal sediments, and along gradients in nitrate and organic matter concentrations. We conducted 2 sampling campaigns, in March and September 2009, during which N2 fluxes were quantified by N2/Ar measurements in sediment core incubations, and compared to isotope pairing results in September 2009. At ambient nitrate concentrations, sediments in the inner Elbe Estuary produced N2 fluxes of up to 156 µmol N m-2 h-1. In September, nitrate concentration in bottom water and organic matter content in sediments limited N2 production; such limitations were not observed in March. We extrapolated the estuarine sediment nitrogen removal of March and September to the present-day area of intertidal and subtidal sediments in the Elbe Estuary between the port of Hamburg and the transition to the North Sea. Our estimate suggests that 3.3 ± 1.2 kt nitrate-N are removed in sediments in this region in spring and summer. This implies that reactive nitrogen removal in the inner Elbe Estuary reduces the spring/summer load of the Elbe River (47 kt N) by around 7%, a reduction that is much lower than commonly assumed for estuaries, and significantly lower than nitrate removal in the Elbe was in historical times.

KEY WORDS: Denitrification · Nitrogen cycle · Eutrophication · Elbe Estuary

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Cite this article as: Deek A, Dähnke K, van Beusekom J, Meyer S, Voss M, Emeis K (2013) N2 fluxes in sediments of the Elbe Estuary and adjacent coastal zones. Mar Ecol Prog Ser 493:9-21.

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