Rivers and streams are part of the freshwater biome, and they experience different climates along their lengths. At the source, these waterways have cooler temperatures and clearer water. As the water travels towards the mouths of tributaries, it warms, encouraging more plant and animal diversity.
Underground springs, overflowing lakes and snow melt all give birth to rivers and streams. The heavily oxygenated water travels one way, usually on its way to a larger river, estuary, bay or ocean. Trout and salmon thrive in this section, but aquatic plants and algae are limited because photosynthesis isn't as efficient at low temperatures. Plants use photosynthesis to convert carbon dioxide and water into sugar and oxygen.
As the water travels downstream, the waterway increases in volume and width. Curves and rocks in the river slow its motion and the temperature starts to rise, allowing plant life to take hold. Animals such as beavers help alter the flow, as does the sediment picked up along the way.
Once the water reaches the mouth of the river or stream, it is murky with less oxygen and supports species such as catfish and carp. The warmer temperatures encourage growth of marsh plants and trees, which attract amphibians, reptiles and filter-feeding birds, such as ducks. This is the wetlands, the bridge between the freshwater and saltwater biomes. The warmer water temperature and the diversity of life increases the humidity, which in turn warms the air and landscape.