Answer:
a food web
Step-by-step explanation:
What they saw was a food web, which refers to connections of food chains showing how energy and nutrients are transferred from one organism to the other.
In this example, we observe there are seven organisms (fish, algae, snails, insects, frogs, raccoons + bacteria contained in the pond) in focus here.
The green algae are Producers (because it produces its own food, not dependant on others)
The bacteria act as Decomposers. ( because they process organic waste into meaningful natural nutrients again)
The other organisms are Consumers. (because they are dependant on others for their nutrition).