Estuary Information:

Estuaries are nearly always eutrophic, receiving nutrients and water from the rivers draining large land areas. Estuaries are major transition zones between fresh and saltwater. Many fishes breed in and live in the estuary zone, and some actually live in either freshwater (upriver) or saltwater (down-river). Many migratory birds that move from continent to continent have stopovers in estuaries. Unfortunately, many estuaries in North America are dying due to pollution. The Colorado river no longer meets the Gulf of California and its estuary has completely died. The Mississippi River estuary is causing red tide algal blooms in the Gulf of Mexico that can be seen from the space shuttle. Fish kills are common. Common plants include algae and marsh plants of all types, such as cattails and salt grass. Common animals include egrets, herons, eagles, bass, and many fish species. Snakes and alligators are common in the southern estuaries.

Mouth of the Amazon

NASA [Public Domain] via Wikimedia Commons.

The exposed intertidal flats along an estuary at low tide.

Lisa Jarvis [CC-BY-SA-2.0], via Wikimedia Commons

A satellite image of the Colorado River estuary.

By Earth Observations Laboratory, Johnson Space Center. [Public domain], via Wikimedia Commons

Mississippi River delta at the Gulf of Mexico

By ASTER data (direct) [Public domain], via Wikimedia Commons

Estuaries are found wherever there is enough river/stream system water to flow to the sea.