An aquatic ecosystem is an ecosystem in a body of water. They are contrasted with terrestrial ecosystems which are those found on land. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.Freshwater ecosystems may be Lentic (slow moving water, including pools, ponds, and lakes); lotic (faster moving water, for example streams and rivers); and wetlands (areas where the soil is saturated or inundated for at least part of the time)