Many people don't know the importance of freshwater biomes. 97.5% of all water on Earth is salt water, leaving only 2.5% as fresh water. Nearly 70% of that fresh water is frozen in the icecaps of Antarctica and Greenland. The plants and animals have adapted to the freshwater and would not be able to survive in areas of high salt concentration. Freshwater has less than 1% salt in it. Biotic factors are water bugs, ducks, fish, plants, and mussels. Abiotic factors are rocks, dirt and water.
Ponds & Lakes
During the summer the temperature can range from 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottom can be 4° C and the top is 0° C. Ponds and lakes have limited species diversity because they are seperate from other water sources. They're divided into three different “zones” which are usually determined by depth and distance from the shoreline. The zone near the shore is the littoral zone. This zone is the warmest since it is shallow and has more of the sun's heat. Here you'd find lots of algae, rooted and floating plants, snails, clams, insects, fishes and amphibians.
The open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well lighted and is dominated by plankton. Plankton are small organisms and without them there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also live in this zone.
The profundal zone is much colder than the other two. Little light gets this far. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.
Streams & Rivers
These are bodies of flowing water that move in one direction. The temperature is cooler at the source than it is at the mouth. The water is also clearer and has higher oxygen levels. Towards the middle part of the river the width increases and so does the number of different kinds of species. Toward the mouth of the river the water becomes murky, decreasing the amount of light that can get through the water. Since there is less light, there is less diversity of flora, and because of the lower oxygen levels, fish that require less oxygen can be found there. In a stream or river you would find catfish, carp, trout, heterotrophs, aquatic green plants, and algae.
Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands. They have the highest species diversity of all ecosystems. Plant species adapted to the very moist and humid conditions are called hydrophytes. Pond lilies, cattials, sedges, tamarack cypress, gum, black spruce, amphibians, reptiles, and ducks all survive in the wetlands.