Marine Ecology North Sea - Baltic Sea model
Dansk version
The marine biogeochemical model ERGOM

ERGOM was originally developed by Neumann et al. (2002) to feature the Baltic Sea Ecosystem. The model provides a full mathematical description of the behavior of marine ecology state variables due to these biogeochemical processes:

  • photosynthesis
  • grazing
  • respiration
  • mortality
  • mineralization
  • nitrification
  • denitrification

ERGOM has nine state variables:

  • dissolved nutrients
    • ammonium
    • nitrate
    • phosphate
  • phytoplankton (primary production)
    • diatoms (grow in nutrient-rich conditions)
    • flagellates (grow in nutrient-poor conditions)
    • blue-green algae (cyanobacteria, fix atmospheric nitrogen)
  • zooplankton (graze on phytoplankton)
  • detritus (dead plankton, some of which enter the sediment)
  • dissolved oxygen

ERGOM is nitrogen-based, and the balance of phosphorus/oxygen is based on nitrogen using stoichiometric Redfield ratios. The concentration of dissolved oxygen controls processes as denitrification and nitrification. Hydrogen sulfate is included as a deficit in the oxygen balance. Detritus in the sediment is either buried, mineralised or resuspended into the water column, depending on the velocity of near-bottom currents.

DMI/ERGOM model set-up

DMI/ERGOM is coupled with a version the DMI North Sea - Baltic Sea ocean circulation model HBM in high spatial resolution. DMI/ERGOM runs twice daily for a 60 hour marine ecology forecast.


DMI/ERGOM is initialized using marine ecology data from the ICES (International Council for the Exploration of the Sea) Oceanographic Data Centre. For time progression, DMI/ERGOM is forced with nutrient loadings from the following sources:

  • nutrient loadings from land-based sources, derived from the daily operational output of the hydrological E-hype3 model run at the Swedish Meteorological Hydrological Institute (SMHI) for all of Europe.
  • atmospheric dry precipitation of nitrogen and phosphorus is neglected, as we focus on the annual cycle in the euphotic layers.
  • open boundary conditions towards the Atlantic are configured using the climatology of ICES data.

DMI/ERGOM gives full 3-d information about nine state variables (see below), in a time resolution of one hour.

The forecast page presents some of this output:

  • near-bottom dissolved oxygen
  • surface total chlorophyll-a
  • surface Nitrate
for the upcoming two days.


Neumann, T., Towards a 3-D ecosystem model of the Baltic Sea, J. Mar. Syst., 25, 405-419, 2000.

Neumann, T., W. Fennel, and C. Kremp, Experimental simulations with an ecosystem model of the Baltic Sea: A nutrient load reduction experiment, Global Biogeochemical Cycles, 16, 10.1029/2001GB001,450, 2002.

Wan, Z., Jonasson, L., Bi, H., 2011. N/ P ratio of nutrient uptake in the Baltic Sea. Ocean Sci. 7, 693–704.

Wan, Z., She, J., Maar, M., Jonasson, L., Baasch-Larsen, J., 2012. Assessment of a physical-biogeochemical coupled model system for operational service in the Baltic Sea. Ocean Sci. 8, 683-701.


Zhenwen Wan, Tian Tian, Jacob W Nielsen - July 11th 2016