The Baltic Sea is the home of tens of fish species, and its islands are inhabited by a variety of different birds. What do these animals eat?

The food chain always begins at the level of producers – small algae and cyanobacteria, and larger plants. Large plants do not grow in the open sea of the Baltic, which means that the producers of these regions are solely algae. As these algae are microscopically small and flow freely in the water, they are considered part of the plankton. 

The numbers of blue algae, green algae and diatom algae begin to increase during the spring, when the ice cover has melted and the increasing amount of sunlight makes photosynthesis possible. In addition to sunlight, the algae also require nutrients, such as nitrogen and phosphorous. During the spring these nutrients are plentiful, and the algae make use of this by reproducing with great speed during the spring.​

The group of zooplankton consists of microscopic organisms such as water fleas and copepods. Zooplankton are consumers that eat producer algae. In turn, these zooplankton are the food of small fish species such as the herring. The top of the food chain of the Baltic sea is inhabited by predators such as the pike, the white-tailed eagle, and the Baltic ringed seal.

Consumers in the food chain of the Baltic Sea. Zooplankton (pictured: copepod) eats microscopic algae. Herrings eat zooplankton and larger fishes, such as the pike, eat herrings. Ringed seals are fourth degree consumers. 

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Bladderwrack or kelp is a key species of the Baltic Sea.