(image Uwe Kils)
Phytoplankton (phyto: vegetal) are small algae and fungi that hover in the water. They obtain energy by photosynthesis, and live mostly on the upper part of the sea, because they need light to survive. They perform the primary production and are the basis for all foodchains in the ocean and freshwaters. Plankton animals have developed sophisticated net-like structures  to filter them out of the water. One of the most remarkable and direct food-chain is phytoplankton - krill - whales.