Journal article
Radium isotopes quantify vertical mixing and reveal large benthic silicate fluxes in anoxic deep waters
Limnology and oceanography, Vol.70(8), pp.2332-2347
08/2025
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Abstract
Benthic fluxes are important sources of nutrients and dissolved carbon to the water column. Yet, most approaches for quantifying benthic fluxes are labor intensive and cover relatively small areas of the ocean. Here, we use 224 Ra to quantify ecosystem‐scale vertical mixing across a largely hypoxic deep water column in the Baltic Sea and related benthic Si fluxes. Bottom water profiles from 50 stations along a ~ 5000 km cruise track in the Baltic Sea revealed highest 224 Ra activities in the deep anoxic basins near the sediment source. Dissolved Si concentrations reached 110 μ M and followed a similar trend to radium. For the radium‐based vertical mixing model, 26 out of 50 stations satisfied the required assumptions. When criteria were met, the radium profiles resolved vertical mixing rates on the order of 10 −4 m 2 s −1 and median dissolved Si fluxes of 5.9 mmol m −2 day −1 , both well within the range of previous local scale estimates based on modeling and sediment core incubations. Extrapolated benthic dissolved Si fluxes were 32 times greater than river dissolved Si flux to the Baltic Sea, highlighting the large contribution of seafloor sources to the water column.
Details
- Title
- Radium isotopes quantify vertical mixing and reveal large benthic silicate fluxes in anoxic deep waters
- Creators
- Tristan McKenzie - University of GothenburgAprajita Singh Tomer - University of GothenburgTibaud Cardis - University of GothenburgClaudia Majtényi-Hill - University of GothenburgBeata Szymczycha - Polish Academy of SciencesPer O. J. Hall - University of GothenburgShibin Zhao - Ocean University of ChinaStefano Bonaglia - University of GothenburgMichael Ernst Böttcher - Leibniz Institute for Baltic Sea Research WarnemündeIsaac R. Santos - University of Gothenburg
- Publication Details
- Limnology and oceanography, Vol.70(8), pp.2332-2347
- Publisher
- Wiley; HOBOKEN
- Grant note
- Funding for this project was supported bythe Knut and Alice Wallenberg Foundation (grant number2022.0096, awarded to Isaac R. Santos) and a Formas Early Career Researcher Grant (grant number 2023-01324, awarded to Tristan McKenzie).
- Identifiers
- 991013296940602368
- Copyright
- © 2025 The Author(s).
- Academic Unit
- Faculty of Science and Engineering; National Marine Science Centre
- Language
- English
- Resource Type
- Journal article