In an oligotrophic water body, meaning low in nutrients, the growth of algae, aquatic plants, and cyanobacteria is limited. This is referred to as a "young" water body. These types of water bodies are poor in phosphorus, the nutrient often limiting in aquatic environments.

As the phosphorus concentration increases, the growth of organisms is no longer limited, and they can proliferate in the environment, causing significant changes in the ecosystem over time.

The more plants and algae proliferate, the more organic matter settles at the bottom of the water. The bacteria responsible for decomposing this matter consume more dissolved oxygen. This can lead to an oxygen deficit for other aquatic organisms, such as fish.

The presence of suspended matter in the water, such as microscopic algae, also reduces water transparency, causing it to warm up.

Over time, the formerly oligotrophic water body will become mesotrophic, meaning a medium-level nutrient concentration. As the process progresses, the water body will become eutrophic, meaning rich in nutrients.

Eutrophication is a natural process that can be accelerated and amplified by human activities. For example, the spreading of fertilizers contains a lot of phosphorus and nitrogen, which often end up in water bodies after heavy rains, enriching them with nutrients.