The Effects of Hypoxia on Sediment Nitrogen Cycling in the Baltic Sea
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Primary production in the eutrophic Baltic Sea is limited by nitrogen availability; hence denitrification (natural transformation of nitrate to gaseous N2) in the sediments is crucial in mitigating the effects of eutrophication. This study shows that dissimilatory nitrate reduction to ammonium (DNRA) process, where nitrogen is not removed but instead recycled in the system, dominates nitrate reduction in low oxygen conditions (O2 <110 μM), which have been persistent in the central Gulf of Finland during the past decade. The nitrogen removal rates measured in this study show that nitrogen removal has decreased in the Gulf of Finland compared to rates measured in mid-1990s and the decrease is most likely caused by the increased bottom water hypoxia.
KeywordsBaltic Sea Sediment Hypoxia Nitrogen Denitrification DNRA
We acknowledge the funding provided by the Onni Talas Foundation, Academy of Finland (116477), and EU-Bonus projects Assessment and Modeling of Baltic Ecosystem Response (AMBER) and Hypoxia Mitigation for Baltic Sea Ecosystem Restoration (HYPER). We are grateful for the constructive comments provided by Juha Niemistö, Heidi Holmroos, and an anonymous reviewer.
- Alenius, P., and R. Hietala. 2008. Happitilanne. In MERI – Report Series of the Finnish Institute of Marine Research No. 64, ed. M. Raateoja, Helsinki, Finland (In Finnish, English summary).Google Scholar
- Diaz, R.J., and R. Rosenberg. 1995. Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna. Oceanography and Marine Biology 33: 245–303.Google Scholar
- HELCOM. 2009. Eutrophication in the Baltic Sea. An integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region. Baltic Sea Environment Proceedings No. 115B, Helsinki, Finland.Google Scholar
- Hietanen, S., H. Jäntti, C. Buizert, K. Jürgens, M. Labrenz, M. Voss, and J. Kuparinen. 2012. Hypoxia and nitrogen processing in the Baltic Sea water column. Limnology and Oceanography. 57: 325–337.Google Scholar
- Jørgensen, K.S. 1989. Annual pattern of denitrification and nitrate ammonification in estuarine sediment. Applied and Environmental Microbiology 55: 1841–1847.Google Scholar
- Kelso, B., R. Smith, R. Laughlin, and D. Lennox. 1997. Dissimilatory nitrate reduction in anaerobic sediments leading to river nitrite accumulation. Applied and Environmental Microbiology 63: 4679–4685.Google Scholar
- Kuparinen, J., and L. Tuominen. 2001. Eutrophication and self-purification: Counteractions forced by large-scale cycles and hydrodynamic processes. Ambio 30: 190–194.Google Scholar
- Lehtoranta, J. 2003. Dynamics of sediment phosphorus in the brackish Gulf of Finland. Monographs of the Boreal Environment Research 24. PhD Thesis, Helsinki, Finland, University of Helsinki.Google Scholar
- Savchuk, O.P. 2010. Large-scale dynamics of hypoxia in the Baltic Sea. In Chemical structure of pelagic redox interfaces: Observations and modelling, handbook of environmental chemistry, ed. E.V. Yakushev. Berlin: Springer.Google Scholar
- Sørensen, J., J.M. Tiedje, and R.B. Firestone. 1980. Inhibition by sulfide of nitric and nitrous oxide reduction by denitrifying Pseudomonas fluorescens. Applied and Environmental Microbiology 39: 105–108.Google Scholar