Low levels of dissolved salts characterise the freshwater biomes. The salt content of fresh water is about 0.005 percent. The freshwater biomes consist of inland bodies of standing water like lakes, reservoirs, ponds and wetlands as well as the flowing waters of the streams and rivers. Their nature does not depend as much on global climate, but on the individual site where they occur.
A lake or a body of standing water can be divided into three zones according to penetration of sunlight in the water body i.e., littoral , limnetic and profundal. Each of these have their own physico -chemical features and characteristic array of living organisms.
The littoral zone is the area where light penetrates to the bottom. Aquatic life in the littoral zone consists of free floating and rooted plants, many aquatic insects, snails, amphibians, fish, turtles and water birds.