Fertilizer creates phytoplankton, microscopic plants and animals. They are the start of the food chain. They are green colored. They change the clarity of the water from clear to "cloudy". This is called the algae bloom. They also create oxygen during the daytime, from sunshine, and use it at night. Think of the word "holiostic" and you see that all parts of the chain must be represented and balanced.
Probably a lot better way of expressing this but it is the general idea.
