What Is an Estuary?

An estuary is a partially enclosed coastal body of water where freshwater from rivers, streams, and rainfall mixes with saltwater from the ocean. This mixing zone — called brackish water — creates one of the most productive and biologically diverse ecosystems on Earth. The Indian River Lagoon (IRL) stretches 156 miles along Florida's east coast and is home to over 4,300 species of plants and animals. More than 700 species of fish have been recorded in the IRL, and estuaries are often called the 'nurseries of the sea' because so many species spawn and grow here. The unique balance of fresh and salt water is what makes the IRL one of the most biodiverse estuaries in North America, and understanding how that balance works is the key to protecting it.