Ponds and Lakes
Ponds and lakes are the biggest type of freshwater biome. The top most layer of water is called the littoral zone, and it is usually the warmest zone due to it directly absorbing most of the sun's heat. The zone that is directly under the littoral zone is the limnetic zone, which is well lighted and usually a couple degrees Celsius colder than the littoral zone. The profundal zone is at the bottom of the pond or the lake and much fewer sun's rays get to the profundal zone, making it colder and darker than the other two. Depending on the time of year, the littoral zone can be up to 20 degrees warmer than the bottom. In the winter when the water freezes, the ice rests at the top at 0 degrees Celsius while the bottom is around 4-5 degrees Celsius.
Streams and Rivers
Bodies of flowing water that flow in a certain direction to a larger body of water. The water is clearer due to the high oxygen levels in the river which allows the sun's rays to pass through easier making it warmer. The temperature at the mouth of a river is warmer than the source of the river due to the friction from the water flowing down the river. The mouth is also usually a lot murkier from the rocks and debris the water picks up as it goes.
All wetlands are located in a place where no water can escape. The water is warmed and cooled according to the weather. Wetlands all have soil that is saturated with water and retains heat very well. In the summer, the top of the wetland is warmed by the sun but in the winter, the soil retains it's heat that it has absorbed over the summer while the water is cooled. Depending on the area, the temperature varies. In the Arabian Peninsula, the temperatures can reach up to 50 degrees Celsius, whereas in Siberia, the temperature can get as low as -58 degrees Celsius. .http://www.thewildclassroom.com/biomes/lake.html