Baltic Sea Food Web
Marine
Northern Europe — between Scandinavia and Continental Europe
Description
The Baltic Sea is one of the world's largest brackish water bodies, with salinity declining from west to east. This gradient creates a unique food web where marine, freshwater, and brackish-adapted species coexist. Cod, herring, and sprat form a three-species interaction central to Baltic fisheries management.
Trophic Pyramid
Level 5
Decomposers
Anaerobic bacteria
Amphipods
Benthic isopods
3 species
Level 4
Tertiary Consumers
White-tailed eagle
Harbour porpoise
2 species
Level 3
Secondary Consumers
Baltic cod
Perch
Grey seal
3 species
Level 2
Primary Consumers
Baltic herring
Sprat
Bay barnacle
3 species
Level 1
Producers
Bladderwrack
Diatoms
Blue-green algae
3 species
Apex Predators
Tertiary Consumers
Secondary Consumers
Primary Consumers
Producers
Key Interactions
- Cod collapse released sprat populations, which then suppressed cod egg survival through predation
- Cyanobacterial blooms are triggered by excess nitrogen and phosphorus loading
- Grey seals have recovered and now interact with cod fisheries through competition
- Hypoxic dead zones in deep basins eliminate benthic food web components