Some phytoplankton actively change their position in the water column
- This process is called vertical migration
- Dinoflagellates and larger flagellates: migrate towards deeper water during night to assimilate nutrients and ascent in the morning for photosynthesis during daylight
- Cyanobacteria: can adjust their position in the water column by gas vesicles. These are laterally-connected cylindrical tubes of protein lacking any membrane
