An estuary is a coastal area where fresh water from rivers and streams mixes with saltwater from the ocean. Many bays, sounds, and lagoons along coasts are estuaries. Portions of rivers and streams connected to estuaries are also considered part of the estuary. The land area from which fresh water drains into the estuary is its watershed.
Estuaries come in all shapes and sizes, each unique to their location and climate. Bays, sounds, marshes, swamps, inlets, and sloughs are all examples of estuaries. An estuary is a fascinating place from the largest landscape features to the smallest microscopic organisms. When viewing an estuary from the air, one is practically amazed by dramatic river bends as freshwater finds its way back to the sea.
The vast expanse of marsh grasses or mudflats extends into calm waters that then follow the curve of an expansive barrier beach. Wherever there are estuaries, there is a unique beauty.
As rivers meet the sea, both ocean and land contribute to an ecosystem of specialized plants and animals. At high tide, seawater changes estuaries, submerging the plants and flooding creeks, marshes, panes, mudflats, or mangroves, until what once was land is now water.
Throughout the tides, the days, and the years, an estuary is cradled between outreaching headlands and is buttressed on its vulnerable seaward side by fingers of sand or mud. 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 decline, 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 shorebirds stilt through the shallows, lunging long bills at their abundant prey of fish, worms, crabs, or clams. Within the sediments, whether mud, 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 saltwater. Estuaries provide habitat; tens of thousands of birds, mammals, fish, and other wildlife depend on estuaries.
They provide marine organisms, most commercially valuable fish species included, depend on estuaries at some point during their development. Where productivity is concerned, a healthy, untended estuary produces from four to ten times the weight of organic matter produced by a cultivated cornfield of the same size. Estuaries provide water filtration; water draining off the uplands carries a load of sediments and nutrients.
As 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.
Estuaries also provide flood control. Porous, resilient salt marsh soils and grasses absorb flood waters and diffuse 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.
Estuaries are significant to both marine life and people. They are critical for the survival of fish, birds, and other wildlife because they provide safe spawning grounds and nurseries. Marshes and other vegetation in the estuaries protect marine life and water quality by filtering sediment and pollution.
They also provide barriers against damaging storm waves and floods. Estuaries also have economic, recreational, and aesthetic value. People love water sports and visit estuaries to boat, fish, swim, and just enjoy their beauty. As a result, the economy of many coastal areas is based primarily on the natural beauty and bounty of their estuaries. Estuaries often have ports serving the shipping, transportation, and industry.
Healthy estuaries support profitable, commercial fisheries. In fact, almost 31 percent of the Gross National Product (GNP) is produced in coastal counties. This relationship between plants, animals, and humans makes up an estuary’s ecosystem. When its components are in balance, plant and animal life flourishes.
Humans have long been attracted to estuaries. Indian mittens 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 even poets and painters 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 populated, 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.
In recognition to these threats, Congress, in 1987, established the National Estuary Program (NEP) as part of the Clean Water Act. The NEP’s mission is to protect and restore the health of estuaries while supporting economic and recreational activities.
To achieve this, the Environmental Protection Agency (EPA) helps create local NEPs by developing partnerships between government agencies that oversee estuarine resources and the people who depend on the estuaries for their livelihood and quality of life.
These groups plan and implement programs according to the needs of their own areas. Local NEPs are demonstrating practical and innovative ways to revitalize and protect their estuaries. The benefit of this program is that it brings communities together to decide the future of their own estuaries.
One specific estuary is the San Francisco Estuary. Human activities in the 1600 square mile Bay/Delta watershed region have drastically altered natural habitats and impaired the functions of the estuary’s ecosystem.
Poor cattle grazing practices contribute to soil erosion and water quality problems. In model public or private partnership, this NEP is assisting a private rancher in developing a grazing management strategy for a 500-acre parcel of public land within Wildcat Creek Regional Park. Strategies already being implemented include building barriers to prevent livestock from trampling sensitive habitats, installing pens to improve livestock management, and selecting a cattle grazing period to retard the growth of alien and nuisance plants.
These measures encourage the regrowth of native bunchgrasses and fords that provide not only better habitat for wildlife, but also more desirable forage for the cattle. In addition, soil erosion and pollutant loading should decrease. Another interesting and problematic estuary is New York-New Jersey Harbor Estuary. Trash and other foldable marine debris washing up on area beaches had been a chronic problem for the New York-New Jersey Harbor Estuary, but unusual episodes in 1987 and 1988 shocked the public and closed many beaches.
The New York-New Jersey Harbor GNP developed a short-term plan using helicopters and vessels for surveillance and capture of the foldable debris. A long-term plan to address the floatables problem was subsequently developed. This included the purchase of additional skimmer vessels to collect debris, a pollution decrease strategy, and an Operation Clean Shores program in New Jersey that has already removed 10,000 tons of debris.
There are many estuaries in the United States that are in the NEP. There are also small estuaries. Such resources include the Mississippi and Alabama estuaries. The GNP, National Estuary Program’s basic purpose is to bring new life to present-day estuaries.