Until recently, most people did not appreciate how much of an effect land ecosystems have on freshwater ecosystems.
Aquatic ecosystems go through a natural aging process once they are formed.
This aging process is called eutrophication , from the Greek word eutrophus , meaning well fed, or well nourished. In ecological terms, this means that nutrients are slowly added to a pond or lake over time by natural processes. In addition to the nutrients that come from the aquatic plants and animals themselves, other nutrients are continually added to an aquatic system from surrounding land ecosystems. These sources include soil erosion and runoff, and organic material, such as plant and animal matter that finds its way into the ecosystem. Decomposers convert their bodies and waste into particulate organic matter, which gets incorporated into the ground.