Estuaries transform with the tides, the incoming waters seemingly bringing back to life organisms that have sought shelter from their temporary exposure to the non-aquatic world. As the tides ebb, organisms return to their protective postures, receding into sediments and adjusting to changing temperatures. The community of life found on the land and in the water includes mammals, birds, fish, reptiles, shellfish, and plants all interacting within complex food  webs. Flocks of shore birds stilt through the shallows, lunging long bills at  their abundant prey of fish, worms, crabs or clams. Within the sediments, whether mud, silt, sand or rocks, live billions of microscopic bacteria, a lower  level of the food web based largely on  decaying plants. Estuaries are tidally-influenced ecological systems where rivers meet the sea  and fresh water mixes with salt water. Estuaries provide:
HABITAT: Tens of thousands of birds, mammals, fish, and other wildlife depend on estuaries.
NURSERY : Many marine organisms, most commercially valuable  fish species included, depend on estuaries at some point during their development.
PRODUCTIVITY : A healthy, untended estuary produces from four to ten times the weight of organic matter produced by a cultivated corn field of  the same size.

WATER FILTRATION: Water draining off the uplands carries a load of sediments and nutrients. As the water flows through salt marsh peat and  the dense mesh of marsh grass blades, much of the sediment and nutrient load is  filtered out. This filtration process creates cleaner and clearer water.
FLOOD CONTROL: Porous, resilient salt marsh soils and grasses absorb flood waters and dissipate storm surges. Salt marsh dominated estuaries  provide natural buffers between the land and the ocean. They protect upland organisms as well as billions of dollars of human real estate.

Estuaries are crucial transition zones between land and water that provide an  environment for lessons in biology, geology, chemistry, physics, history, and  social issues.
Humans have long been attracted to estuaries. Indian middens consisting
of shellfish and fish bones are reminders of how ancient cultures lived. Since Colonial times we have used estuaries and their connecting network of rivers for transporting agricultural goods for manufacturing and trade. Not only do commercially important fish and shellfish spawn, nurse, or feed in estuaries, estuaries also feed our hearts and minds. Scientists and students, poets and  painters, bird watchers and canoeists - all are inspired by the beauty and diversity found in an estuary.

Human activity also seriously threatens the vulnerable ecosystems found in the estuaries. Long considered to be wastelands, estuaries have had their channels dredged, marshes and tidal flats filled, waters polluted, and shorelines reconstructed to accommodate our housing, transportation, and agriculture needs. As our population grows and the demands imposed on our natural resources increase, so too does the importance of protecting these  resources for their natural and aesthetic values.
 Recognizing these human threats and the natural value of estuaries, Congress created the National Estuarine Research Reserve System (NERRS) in 1972. NERRS is dedicated to fostering a system of estuary reserves that represents the wide  range of coastal and estuarine habitats found in the United States and its  territories. In pursuit of this goal, NERRS works with Federal and State  authorities to establish, manage, and maintain reserves, and to provide for  their long-term stewardship. Research and education are also crucial to meeting this goal. NERRS reserves serve as laboratories and classrooms where the effects of both natural and human activity can be monitored and studied. Currently 425,000 acres in 18 states and Puerto Rico are protected by NERRS. Through careful stewardship of these vital natural resources, generations of scientists, fishermen, and bird-watchers will come to experience the beauty to be found where rivers meet the sea.