IOW Logo

Modelling the ecosystem

To get the full picture, what is happening in the Baltic Sea, coupled models are a widely used toolkit. Therefore, IOW's biogeochemical model ERGOM is linked with a three-dimensional circulation model, like MOM or GETM. ERGOM itself is a classical NPZD-model, including different Nitrogen and Phosphorus sources, three functional phytoplankton groups and further zooplankton and detritus, which is permanently developed further. Due to the coupling it is ensured, that phytoplankton blooms are transported by the currents or that resuspension of sediment takes place.

 

Annual cycle of surface phytoplankton

Baltic Sea´s phytoplankton (converted to Chlorophyll a) shows classically two peak. First one during the spring bloom, when enough nutrients are available and the physical conditions (water temperature & light) are sufficient. During summer usually a second peak takes place, when nitrogen-fixing cyanobacteria occur.

Annual cycle of Dissolved Inorganic Nitrogen

Usually, Dissolved Inorganic Nitrogen (DIN) enriches during winter, when biological activity is lowest. During spring bloom, it is than more or less completely consumed. On this low level, it stays until phytoplankton´s activity decreases again in late autumn. The only exception are the coastal waters of the southern Baltic Sea, which are permanently supplied by high river loads.