Answer:
Phytoplanktons are single celled organisms found in aquatic ecosystems. They make their own food by capturing sunlight for photosynthesis. Example of some phytoplanktons are diatoms, dinoflagellates and cynobacteria ( blue green algae). Phytoplanktons functions as the primary producers of the aquatic ecosystem. They attain the bottom level in the energy pyramid and store certain amount of suns energy and convert it into food. The energy derive from food is transferred to higher energy levels in the energy pyramid as phytoplanktons are eaten up by many aquatic animals. Therefore, the energy transferred from phytoplankton to higher energy levels gets decreased according to 10% law which says, energy decreases 10% at each higher trophic level. So, all the energy stored by the phytoplankton will not reach the top level of the pyramid.