Plankton
Plankton
Plankton is the lower part of the food chain. It is divided into two main groups, consisting of phytoplankton and zooplankton. The phytoplankton is responsible for photosynthesis in the ocean just as green leaves do on land. Besides binding CO2 and producing oxygen, it is food for zooplankton. If this link is broken, the term "black sea" could have a global meaning.