Why do plants flourish in estuaries?
Drawing A A salt wedge In estuaries, fresh water is lighter than seawater and therefore flows above it. The flow of some rivers is so immense that a wedge-shaped bottom layer of salt water is pushed up the estuary along the river bottom, carrying with it nutrients for the estuarys plant life. The mixing of fresh water and salt water is an important feature of estuaries. The fresh water is less dense (lighter) than seawater and therefore flows above it (see Drawing A). The flow of some large rivers is so immense that a wedge-shaped bottom layer of salt water, called a salt wedge, is pushed up the estuary along the river bottom by the force of the outgoing fresh water above it. This wedge of salt water can penetrate several kilometres from the rivers mouth, carrying with it nutrients for the estuarys plant life from the ocean. Drawing B Productive ecosystems Estuaries are among the most biologically productive ecosystems on Earth. The drawing shows how much more plant material grows in e
