They are Texas's most valuable natural resource. This resource depends directly on inflows of fresh water. Estuaries are some of the most productive ecosystems in the world. They are tough and resilient. Salinities can range from full seawater to fresh in a season.
Estuaries provide a broad range of conditions that call for tough, adaptable species.
There is a diversity of life, but the ecosystem is dominated by a relative few, hardy and prolific species adapted to the vagaries of estuarine conditions. This also is why estuaries are so productive. Shrimp, crabs, redfish, oysters and other species use all the estuaries' resources to produce the huge numbers we harvest for both commercial and recreational purposes. These species are adapted to use the marshes, nutrients and salinity gradients provided by freshwater inflows, and dominate life in our estuaries. In order to comprehend the complex nature of an estuary, think of it as a factory whose products are the seafood and recreation we enjoy.