19 Jan 2021

19 Jan 2021

Review status: this preprint is currently under review for the journal BG.

Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Astrid Hylén1, Sebastiaan J. van de Velde2, Mikhail Kononets1, Mingyue Luo3, Elin Almroth-Rosell4, and Per O. J. Hall1 Astrid Hylén et al.
  • 1Department of Marine Sciences, University of Gothenburg, 413 19 Gothenburg, Sweden
  • 2Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
  • 3Department of Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, 1050 Brussel, Belgium
  • 4Oceanographic Research, Swedish Meteorological and Hydrological Institute, 426 71 Västra Frölunda, Sweden

Abstract. Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom-water conditions, phosphorus release from the sediment is elevated which further stimulates primary production. It is commonly assumed that re-oxygenation could break this ‘vicious cycle’ by increasing sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in-situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this three-year-long study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment. As a result, the net sedimentary DIP release per m2 was 35–70 % higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.

Astrid Hylén et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-5', Anonymous Referee #1, 05 Feb 2021
  • RC2: 'Comment on bg-2021-5', Tom Jilbert, 16 Feb 2021
  • RC3: 'Comment on bg-2021-5', Anonymous Referee #3, 05 Mar 2021

Astrid Hylén et al.

Data sets

Benthic fluxes and sediment properties in the Eastern Gotland Basin, Baltic Sea, following a major Baltic inflow Astrid Hylén, Sebastiaan J. van de Velde, Mikhail Kononets, Mingyue Luo, Elin Almroth-Rosell, and Per O. J. Hall

Astrid Hylén et al.


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Short summary
Sediments in oxygen-depleted ocean areas release high amounts of phosphorus, feeding algae that consume oxygen upon degradation, leading to further phosphorus release. Oxygenation is thought to trap phosphorus in the sediment and break this feedback. We studied the sediment phosphorus cycle in a previously anoxic area after an inflow of oxic water. Surprisingly, the sediment phosphorus release increased, showing that feedbacks between phosphorus release and oxygen depletion can be hard to break.