I believe it’s the sun
As the sun gives nutrients to the plant
Plant gets satin by animal
Animal gets eaten by animal and so on and the nutrients would be passed on
If I am correct it is The Third Trimester
Algae live in bodies of water and damp places and are commonly found in both aquatic and terrestrial environments. Terrestrial algae mostly live in moist, tropical areas. They prefer wet places, because they do not have vascular tissues and the other necessary adaptations to survive on land.