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Marine Ecology Progress Series

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MEPS 604:33-50 (2018)  -  DOI:

Carbon oxidation and bioirrigation in sediments along a Skagerrak-Kattegat-Belt Sea depth transect

Erik Kristensen1,*, Hans Røy2, Kristian Debrabant3, Thomas Valdemarsen1

1Department of Biology, University of Southern Denmark, 5230 Odense M, Denmark
2Center for Geomicrobiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
3Applied Mathematics, Department of Mathematics and Computer Science, University of Southern Denmark, 5230 Odense M, Denmark
*Corresponding author:

ABSTRACT: Partitioning of electron acceptors and macrofaunal bioirrigation were assessed in sediments from 4 stations along a Skagerrak-Kattegat-Belt Sea depth transect. Sediment was examined for benthic fauna composition and abundance, sediment-water fluxes (O2, dissolved inorganic carbon [DIC], NH4+, and NO3-), anaerobic reactions (carbon oxidation [Cox], sulfate reduction [SR], manganese reduction [MnR], iron reduction [FeR], and ammonification [Nmin]), porewater profiles (O2, DIC, SO42- and NH4+), and solid phase profiles (organic content, Fe and Mn). Deep stations had less than half the abundance of benthic fauna than shallow stations, while the Belt Sea station was azoic due to bottom-water hypoxia. Solute fluxes and anaerobic reactions showed order-of-magnitude lower rates in sediment from deep than from shallow water. In general, anaerobic Cox in sediments along the Skagerrak-Kattegat-Belt Sea transect is dominated by SR (>50%) in shallow water and decreases gradually when moving into deeper water and reaches 0 at ~700 m depth. FeR increases from 0 in shallow water to ~50% at ~600 m, but rapidly reaches 0 again at 700 m. MnR is close to 0 down to at least 500 m and increases to complete dominance at 700 m. The contribution of denitrification is generally below 10% at all depths. Bioirrigation—quantified as non-local exchange through diagenetic modelling—is proportional to fauna biomass and functional traits. The Br- tracer approach to determine bioirrigation on newly extracted sediment onboard a ship is not recommended. It is concluded that enhanced downward translocation of O2 into anoxic sediment through bioirrigation is the major mechanism reoxidizing subsurface metals in the deep Skagerrak and Kattegat.

KEY WORDS: Electron acceptor · Carbon oxidation · Benthic fauna · Bioirrigation · Metal oxides · Diagenetic modelling

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Cite this article as: Kristensen E, Røy H, Debrabant K, Valdemarsen T (2018) Carbon oxidation and bioirrigation in sediments along a Skagerrak-Kattegat-Belt Sea depth transect. Mar Ecol Prog Ser 604:33-50.

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