Lotic ecosystems always flow in one direction. Usually they start in the mountains, formed by snowmelt and rain, and they flow downward over theland. They typically last hundreds of thousands of years. Smaller ecosystems such as creeks may dry up each year as the seasons change. The typesof organisms that live in lotic ecosystems depend on many things. Such as how fast the water is flowing, the amount of light, and the temperature.Organisms in lotic systems must be able to adapt to handle the high oxygen content, which is caused by the flowing water. Lotic systems have alow salt content. Animals must be able to prevent excess water from building up in their bodies. Algae and plants provide energy for animals in loticecosystems. Many invertebrates, such as insects, snails, and crayfish, depend on the flowing water to bring them oxygen and nutrients. Fish thatlive in lotic ecosystems must be adapted to survive in flowing water. Many lotic systems connect to each other and form a path to the ocean, sosome fish species spend part of their lives in freshwater and part in the ocean. Other vertebrates spend part of the time on land and part in thewater, such as species of amphibians, reptiles, mammals, and birds. Specific examples include: frogs, salamanders, snakes, turtles, beavers, andriver otters.
Rivers
Animals that live in rivers include fish, some insect larvae andreptiles, such as turtles. Mammals, such as river otters, beaversand muskrats, also live in rivers, as do amphibians, such as frogsand salamanders.
