Freshwater Ecosystem:

An aquatic ecosystem is an ecosystem located in water bodies. The two main types of aquatic ecosystems are freshwater ecosystems and marine ecosystems.

The freshwater ecosystem is defined as having a low salt concentration – usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and cannot survive in areas of high salt concentration (i.e. ocean).

Freshwater ecosystems can be divided into two categories:

Standing water or lentic ecosystems:

• Standing water or lentic ecosystems like a lake, pond, marshes, or swamp. These are also known as pond ecosystems.
• A lake, any relatively large body of slowly moving or standing water that occupies an inland basin of appreciable size.
• Definitions that precisely distinguish lakes, ponds, swamps, and even rivers and other bodies of nonoceanic water are less well established.
• It may be said, however, that rivers and streams are relatively fast-moving (lotic ecosystems); marshes and swamps contain relatively large quantities of grasses, trees, or shrubs; and ponds are relatively small in comparison with lakes.
• Geologically defined, lakes are temporary bodies of water.

Running water or lotic ecosystems:

• A marsh is a wetland that is dominated by herbaceous rather than woody plant species. Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems. They are often dominated by grasses, rushes, or reeds.
• A swamp is a wetland ecosystem characterized by mineral soils with poor drainage and by plant life dominated by trees. Swamps are found throughout the world, most often in low-lying regions (with poor drainage) next to rivers, which supply the swamp with water. Some swamps develop from marshes that slowly fill in, allowing trees and woody shrubs to grow.
• Examples of running water or lotic ecosystems are – rivers, springs and streams.