A1 Journal article (refereed)
Autochthonous organic matter promotes DNRA and suppresses N2O production in sediments of the coastal Baltic Sea (2021)

Aalto, S. L., Asmala, E., Jilbert, T., & Hietanen, S. (2021). Autochthonous organic matter promotes DNRA and suppresses N2O production in sediments of the coastal Baltic Sea. Estuarine, Coastal and Shelf Science, 255, Article 107369. https://doi.org/10.1016/j.ecss.2021.107369

JYU authors or editors

Publication details

All authors or editors: Aalto, Sanni L.; Asmala, Eero; Jilbert, Tom; Hietanen, Susanna

Journal or series: Estuarine, Coastal and Shelf Science

ISSN: 0272-7714

eISSN: 1096-0015

Publication year: 2021

Volume: 255

Article number: 107369

Publisher: Elsevier

Publication country: United Kingdom

Publication language: English

DOI: https://doi.org/10.1016/j.ecss.2021.107369

Publication open access: Not open

Publication channel open access: 

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/75207

Abstract

Coastal environments are nitrogen (N) removal hot spots, which regulate the amount of land-derived N reaching the open sea. However, mixing between freshwater and seawater creates gradients of inorganic N and bioavailable organic matter, which affect N cycling. In this study, we compare nitrate reduction processes between estuary and offshore archipelago environments in the coastal Baltic Sea. Denitrification rates were similar in both environments, despite lower nitrate and carbon concentrations in the offshore archipelago. However, DNRA (dissimilatory nitrate reduction to ammonium) rates were higher at the offshore archipelago stations, with a higher proportion of autochthonous carbon. The production rate and concentrations of the greenhouse gas nitrous oxide (N2O) were higher in the estuary, where nitrate concentrations and allochthonous carbon inputs are higher. These results indicate that the ratio between nitrate and autochthonous organic carbon governs the balance between N-removing denitrification and N-recycling DNRA, as well as the end-product of denitrification. As a result, a significant amount of the N removed in the estuary is released as N2O, while the offshore archipelago areas are characterized by efficient internal recycling of N. Our results challenge the current understanding of the role of these regions as filters of land-to-sea transfer of N.

Keywords: denitrification; nitrogen fixation; coastal waters; deltas; dissolved organic carbon; organic material; sediments

Free keywords: denitrification; DNRA; DOM; estuary; N2O; sediment organic matter

Contributing organizations

Ministry reporting: Yes

VIRTA submission year: 2021

JUFO rating: 1