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Marine Ecology Progress Series

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MEPS 544:77-92 (2016)  -  DOI:

Nutrient fluxes from reduced Baltic Sea sediment: effects of oxygenation and macrobenthos

Nils Ekeroth1,3,*, Sven Blomqvist1, Per O. J. Hall2

1Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91, Stockholm, Sweden
2Department of Marine Sciences, University of Gothenburg, 412 96, Gothenburg, Sweden
3Present address: Selebovägen 1, 122 48 Enskede, Sweden
*Corresponding author:

ABSTRACT: Effects of bottom water oxygenation and macrofaunal colonisation on benthic fluxes of nitrogen (N), phosphorus (P) and silicon (Si) from long-term anoxic Baltic Sea bottom sediment were investigated. Sediment boxcosms from an anoxic site at 150 m depth in the open Baltic proper were incubated in the laboratory to follow the development of benthic nutrient fluxes during 74 d exposure to flow-through of oxygen-rich water. In contrast to traditional end-point experimental designs, our repeated measurement approach allowed for separation of transient and long-term effects of oxygenation and bioturbation on benthic nutrient recycling. The composition, but not the rate, of the benthic total dissolved N efflux changed by oxygenation from being dominated by NH4 in situ to being mostly composed of NO2 + NO3 and dissolved organic N (DON) under oxic conditions. Oxygenation in the boxcosms decreased the benthic efflux of dissolved silicate (DSi) and essentially shut off the in situ flux of dissolved inorganic phosphorus (DIP). After 20 d of oxygenation, 2 bottom macrofauna taxa, the polychaete Marenzelleria spp. and the amphipod Monoporiea affinis, were introduced to a subset of the boxcosms. Bioturbation by either taxa increased the efflux of dissolved inorganic N (DIN), DON and DSi to the overlying water. The P-rich benthic flux under in situ anoxic conditions roughly approached Redfield N:P stoichiometry after oxygenation in the sediment boxcosms. Upon addition of macrofauna, bioturbation generated even higher N:P flux ratios.

KEY WORDS: Bioturbation · Oxygenation · Benthic nutrient fluxes · Baltic Sea · Bottom sediment

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Cite this article as: Ekeroth N, Blomqvist S, Hall POJ (2016) Nutrient fluxes from reduced Baltic Sea sediment: effects of oxygenation and macrobenthos. Mar Ecol Prog Ser 544:77-92.

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