Ecological ReGional Ocean Model with vertically resolved sediments (ERGOM SED 1.0): coupling benthic and pelagic biogeochemistry of the south-western Baltic Sea

Abstract

Sediments play an important role in organic matter mineralisation and nutrient recycling, especially in shallow marine systems. Marine ecosystem models, however, often only include a coarse representation of processes beneath the sea floor. While these parameterisations may give a reasonable description of the present ecosystem state, they lack predictive capacity for possible future changes, which can only be obtained from mechanistic modelling.This paper describes an integrated benthic-pelagic ecosystem model developed for the German Exclusive Economic Zone (EEZ) in the western Baltic Sea. The model is a hybrid of two existing models: the pelagic part of the marine ecosystem model ERGOM and an early diagenetic model by Reed et al. (2011). The latter one was extended to include the carbon cycle, a determination of precipitation and dissolution reactions which accounts for salinity differences, an explicit description of the adsorption of clay minerals, and an alternative pyrite formation pathway. We present a one-dimensional application of the model to seven sites with different sediment types. The model was calibrated with observed pore water profiles and validated with results of sediment composition, bioturbation rates and bentho-pelagic fluxes gathered by in situ incubations of sediments (benthic chambers). The model results generally give a reasonable fit to the observations, even if some deviations are observed, e.g. an overestimation of sulfide concentrations in the sandy sediments. We therefore consider it a good first step towards a threedimensional representation of sedimentary processes in coupled pelagic-benthic ecosystem models of the Baltic Sea.Published by Copernicus Publications on behalf of the European Geosciences Union.

Optical model for the Baltic Sea with an explicit CDOM state variable: a case study with Model ERGOM (version 1.2)

“…Owing to the changed shortwave distribution in the water column, an effect on the biogeochemistry in particular is ex- from simulated salinity in green, and red diamonds are observations. The map was created using the software package GrADS 2.1.1.b0 (http://cola.gmu.edu/grads/, last access: 6 August 2021), using published bathymetry data (Seifert et al, 2008). pected.…”

“…Starting point of the development is the optical model as in the study by Neumann et al (2015). The photosynthetical active radiation (PAR) follows an exponential decay with depth z: The map was created using the software package GrADS 2.1.1.b0 (http://cola.gmu.edu/grads/, last access: 6 August 2021), using published bathymetry data (Seifert et al, 2008).…”

“…All necessary ingredients (the code generation tool, text files, and templates for several systems) can be downloaded from http://www.ergom.net (last access: 22 September 2020). The same technique is used for example in Radtke et al (2019).…”

Baltic Earth Assessment Report on the biogeochemistry of the Baltic Sea

“…In addition to determining the zonation of primary redox reactions, oxygen availability also, directly and indirectly, influences the overall rates of microbial Corg remineralization. Organic matter degradation through sulfate reduction and methanogenesis have slow reaction kinetics (Moodley et al, 2005) and are typically assumed to proceed at half the rate of the higher-energy yield reactions in diagenetic models of Baltic Sea sediments (Radtke et al, 2019;Reed et al, 2011). Hence, respiration of organic matter proceeds more slowly in the sediments of the deep anoxic basins.…”

“…Improvements in sediment typology (e.g. Tauber, 2014) and coupled water column-sediment biogeochemical modelling (Radtke et al, 2019) show the way forward towards a more accurate depiction of spatio-temporal variability, but these tools are not yet viable in all locations due to gaps in data and expertise. A particular problem concerns estimates of process rates, and especially carbon and nutrient burial, in shallow coastal areas of the Baltic Sea.…”