An estuary is a coastal area where saltwater from the ocean mixes with freshwater from rivers, rainfall, and upland runoff.
Within the estuary, salt and fresh water proportions differ daily depending on the season, weather, and tides. Vital coastal ecosystems exist in these constantly changing conditions.
The mixing of salt and fresh water begins offshore, where water, sediment, and nutrients from the Mississippi River mix with the salt water of the Gulf of Mexico. Wind and tides drive this mixture, along with fish and shellfish, into the estuary. Changes on the coast affect water levels and habitats throughout the entire system.