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Understanding and quantifying the scope and scale of sedimentary services in the German Baltic Sea (SECOS II)

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For general information please visit the SECOS homepage [1] or the IOW project database [2].

Work Package 2.3. Modelling sediment services under changing environmental conditions and the influence of macrofaunal key species

The task of work package 2.3 was to model important processes at the sediment-water-interface and in the sediment which are indicative of the retention and long term fate of nutrients. These include:

  • sedimentation rates of organic material,
  • oxygen, nitrogen, phosphorus, and carbon fluxes at the sediment-water-interface,
  • transformation of eutrophic substances into non-reactive forms, e.g. nitrate removal via denitrification,
  • burial of nitrogen and phosphorus compounds in deep sediment layers.

To do this, the Ecological ReGional Ocean Model (ERGOM) was extended to include vertically resolved sediment biogeochemistry (ERGOM SED 1.0) [3,4].

The extended coupled benthic and pelagic diagenetic model includes:

  • continuation of the water column model ERGOM into the pore water of the sediments,
  • vertically resolved representation of the upper sediment layers (~22cm)
  • non-local bio-diffusion in 1D
  • realistic representation of the sediment processes, similar to Reed et al. [2011], iron and manganese oxides, iron monosulfide, pyrite, adsorption of solutes to clay minerals, predictive calculation of pore water pH

Biogeochemische und physikalische Prozesse am Sediment-Wasser-Interface und involvierte Zustandsgrößen im erweiterten ERGOM-SED (Quelle: Hagen Radtke, IOW)

Abbildung 1: Biogeochemische und physikalische Prozesse am Sediment-Wasser-Interface und involvierte Zustandsgrößen im erweiterten ERGOM-SED (Quelle: Hagen Radtke, IOW).

All model simulations for SECOS were performed on High Performance Computing (HPC) clusters of the HLRN (North-German Supercomputing Alliance) [5].

An example of the annual mean modelled oxygen fluxes into the sediment is shown below. The fluxes are highest in the vicinity of the coast, where eutrophication also is highest. In contrast, they are lower in central basins, which contain larger amounts of organic material. White areas indicate regions where the substrate is characterized by rocky seafloor, hence, no biogeochemical processes are activated.

A detailed evaluation of the model results is ongoing.

Sauerstofffluss ins Sediment [mmol m-2 d-1]. Saisonale Mittelwerte von 1991 bis 1999. Weiße Regionen, die kein Land sind, haben einen felsigen Meeresboden für den keine biogeochemischen Prozesse aktiviert sind (Quelle: Bronwyn Cahill, IOW)

Abbildung 2: Sauerstofffluss ins Sediment [mmol m-2 d-1]. Saisonale Mittelwerte von 1991 bis 1999. Weiße Regionen, die kein Land sind, haben einen felsigen Meeresboden für den keine biogeochemischen Prozesse aktiviert sind (Quelle: Bronwyn Cahill, IOW).


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Links and references:

  1. SECOS Homepage: secos.deutsche-kuestenforschung.de/projekt-secos-synthese.html
  2. SECOS Beschreibung in IOW Projektdatenbank: www.io-warnemuende.de/project/141/secos_ii.html
  3. ERGOM homepage: ergom.net/
  4. Radtke, Hagen, et al. "Ecological ReGional Ocean Model with vertically resolved sediments (ERGOM SED 1.0): Coupling benthic and pelagic biogeochemistry of the south-western Baltic Sea." Geosci. Model Dev. Discuss 2018 (2018): 1-42. doi: 10.5194/gmd-2018-109
  5. SECOS Rechenzeitprojekt, Norddeutsche Verbund für Hoch- und Höchstleistungsrechnen (HLRN, Projekt ID: mvk00035): zulassung.hlrn.de/kurzbeschreibungen/mvk00035.pdf

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