A brown fishing pier stretches over reflective water. A yellow sun sets in the blue evening sky.
People today continue to use estuaries as a source of food, means of transportation, and for recreation and enjoyment.

NPS Photo/Breault

Estuaries form where rivers and streams empty into larger bodies of water such as bays and gulfs. Inland freshwater blends with coastal saltwater, creating a mixture called brackish water. This mixture provides an ideal environment for young sea creatures such as fish and shellfish. These areas also provide a source of food and habitat for coastal birds, reptiles, and mammals. Humans have frequented estuaries throughout history due to their abundance of food and proximity to water. People today continue to use estuaries as a source of food, means of transportation, and for recreation and enjoyment. The Davis Bayou Area is an example of an estuarine ecosystem.
Estuaries provide great habitats for local and migratory bird species as well as a diverse collection of marine life. Shallow, calm waters, devoid of larger marine predators, provide ideal conditions for animals such as fish and crab to breed and lay their eggs. This creates a concentration of new life, which in turn provides a consistent food source for other animals. Estuaries also act as a filter, protecting coastal waters from pollutants picked up by rivers and streams as they make their way to the coast. Early explorers to the Gulf Coast searched for estuaries to use as a waterway entrance into unexplored areas of the mainland.
As humans have learned about the importance of estuaries, we have also come to see the negative impacts that we have on their health. Threats to estuaries include human development, pollution, storms, and climate change. Estuaries on the Gulf Coast have been negatively affected by oil spills, drops in water salinity levels, algae blooms, and dredging. It is up to us to continue to learn about and protect these important and vulnerable ecosystems.

Animals in this ecosystem


  • Jack E. Davis (2017). The Gulf: The Making of an American Sea. Liveright Publishing Corporation, New York, New York.

  • Proctor, N. S., & Lynch, P. J. (2012). A field guide to the southeast coast and Gulf of Mexico: Coastal habitats, seabirds, marine mammals, fish and other wildlife. New Haven, CT: Yale University Press.

  • “What is an Estuary” NOAA website,

Last updated: April 21, 2020

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