The effect of sediment resuspension on pelagic nitrogen fixation in a Danish Fjord
Year: 2025
Type: article
Abstract: Sediment resuspension, driven by wind, waves, and tides, mixes benthic and pelagic environments by introducing sediment, nutrients, and microorganisms into the water column. While previous studies suggest resuspension enhances N 2 fixation, its impact remains unclear. Prior to our experiment in the microtidal fjord environment of Kærby Fed (Odense Fjord, Denmark), we experimentally determined the amount of resuspended material under various bed-shear-stress intensities, providing a novel approach to assessing its effects. Contrary to expectations, our data showed no significant increase in N 2 fixation rates under varying resuspension intensities. Instead, rates were influenced by geochemical dynamics, particularly phosphorus release during anoxic events. The diazotrophic community, primarily composed of Proteobacteria related to sulfate-reducing bacteria, was well-represented in the pelagic environment, likely sustaining observed N 2 fixation rates. These findings highlight the importance of environmental conditions in regulating pelagic N 2 fixation and contribute to nitrogen budget assessments for coastal systems. • Sediment resuspension had minimal impact on N 2 fixation near the benthic boundary layer. • Anoxic sediment conditions and release promoted elevated N 2 fixation rates. • Sulfate-reducing bacteria contributed significantly to N 2 fixation in eutrophic fjords. • Only the uppermost millimeter of sediment was resuspended under realistic conditions. • Strong diazotroph community overlap links sediment and pelagic environments.
Institutions: University of Southern Denmark, University of Copenhagen
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: hybrid
Estimated APC paid: $3,410
Awards: G1562253792, G3575683343, G574959246
OpenAlex ID: W4415020240