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

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...

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Bibliographic Details
Published in:Marine ecology. Progress series (Halstenbek) 2016-02, Vol.544, p.77-92
Main Authors: Ekeroth, Nils, Blomqvist, Sven, Hall, Per O. J.
Format: Article
Language:English
Subjects:
Baltic Sea
Benthic nutrient fluxes
Biological Sciences
Biologiska vetenskaper
Bioturbation
Bottom sediment
Brackish
Marenzelleria
Marine
Oxygenation
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Summary: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 Prich 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.
ISSN:0171-8630
1616-1599
1616-1599
DOI:10.3354/meps11592