What is the role of algae in nature? How do people use algae?

Algae, like all plants in nature, are a source of oxygen and food for the inhabitants of water.

In human life, algae are just as important:

source of iodine;
are used by humans for food (kelp – “seaweed”);
agar-agar is obtained from red algae, which is used in the food, perfumery industry and as a nutrient medium in scientific laboratories;
diatoms are used as biological filters;
raw materials for the chemical industry;
sludge – rotting algae residues – fertilizer.