AME 49:293-302 (2007)  -  DOI: https://doi.org/10.3354/ame01146

Effects of short-term anoxia on benthic denitrification, nutrient fluxes and phosphorus forms in coastal Baltic sediment

Susanna Hietanen1,2,*, Kaarina Lukkari3

1Department of Biological and Environmental Sciences/Aquatic Sciences, PO Box 65, University of Helsinki, 00014 Helsinki, Finland
2Tvärminne Zoological Station, University of Helsinki, 10900 Hanko, Finland
3Finnish Institute of Marine Research, PO Box 2, 00561 Helsinki, Finland

ABSTRACT: Whether sediments act as sinks or sources of nutrients depends partly on the oxygen conditions at the seafloor. Laboratory experiments on coastal Gulf of Finland (Baltic Sea) sediment tested the sensitivity of denitrification to a 2 wk anoxia exposure and subsequent reoxidation of the bottom waters. At the same time we followed the rapidly (1 d) and more slowly (9 d) emerging changes in different forms of sediment P after oxic conditions were restored. The total denitrification rate (Dtot) did not change during anoxic incubation, but shifted from coupled nitrification-denitrification (Dn) towards water column nitrate dependence (Dw). As the Dn rate did not decrease at the same rate as the Dw rate increased, the overall effect of 2 wk exposure to anoxia was an increase in Dtot rate. Nitrification was enhanced in the manipulated sediment compared to natural conditions, despite anoxia. Anoxia quickly caused a release of dissolved P from its 2 most labile forms. The effect was readily reversible, but in nature the replenishment of oxygen stores is usually linked to an intense mixing of the water column, and it is possible that part of the P released during anoxia reaches the productive layer. In our experiments, anoxia affected P cycling more than N cycling.


KEY WORDS: Denitrification · Phosphorus fractions · Benthic nutrients · Anoxia


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Cite this article as: Hietanen S, Lukkari K (2007) Effects of short-term anoxia on benthic denitrification, nutrient fluxes and phosphorus forms in coastal Baltic sediment. Aquat Microb Ecol 49:293-302. https://doi.org/10.3354/ame01146

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