What is an Estuary?


1. An estuary is a "bay" or "sound" where fresh water from streams and rivers empties into and mixes with salt water from the ocean. Estuary is another name for bay, sound, inlet, lagoon - what's important is the mixing of fresh and salt water.

2. Estuaries are among the most productive natural systems on earth, producing more food per acre than the richest Midwestern farmland due to the mixing of nutients from land and sea.

3. There are 102 estuaries in the U.S., 28 of which have been designated by their states and the federal government as nationally significant.

4. Estuaries have many different types of habitats, including shellfish beds, sea grass meadows, wetlands, kelp beds, beaches, river deltas and channels, tidal flats, rocky shores, and salt marshes.

5. These habitats are vital to many important species of fish and wildlife. Over 75 of commercial fish depend on the habitat of estuaries.

6. Fishing contributes $111 billion to the nation's economy every year and support at least 1.5 million jobs.

7. About 45% of all endangered and threatened species rely on estuary and coastal waters. Almost 75% of endangered and threatened birds and mammals rely on these waters, as do 30% of all wintering waterfowl.

8. People love estuaries for their beauty and for fishing, swimming, boating, diving, wildlife viewing, hunting, learning, and working. In 1993, over 180 million Americans used estuaries.

9. There's a lot we don't know yet about estuaries, like exactly how many acres of estuary habitats have been destroyed since settlement and exactly how many thousands of acres of estuary habitats continue to be lost every year.

10. We can save estuaries and their habitats! Call Restore America's Estuaries or your local estuary group to find out how you can help restore these beautiful place to health.

To sum it up an estuary is a coastal area where fresh water from rivers and streams mixes with salt water 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 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 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. Because of our love of the water, almost half of the United States population now lives in coastal areas, including shores of estuaries. In addition, coastal counties are growing three times faster than anywhere else. Unfortunately, this increasing concentration of people upsets the balance of ecosystems. People need housing services, and roads, so new industry and businesses arrive to provide them. When severe, such stresses have forced government authorities to close beaches and shellfish beds and issue warnings about eating fish. In addition, removing grass and trees for development can cause soil erosion and reduce natural habitat, which contributes to the threat of extinction of endangered wildlife.





Estuaries have many kinds of habitats that make them important:

Coastal wetlands support 75 percent of the nation's commercial fisheries beaches are enjoyed by millions of people year-round oyster and other shellfish beds provide jobs and recreation mudflats, rocky shores, and river deltas are habitat for 30% of wintering waterfowl in the U.S. kelp beds and sea grass meadows harbor hundreds of different kinds of life. People treasure the shorelines, bays, and beaches of estuaries for fishing, wildlife viewing, boating, hunting, and many other leisure and job-related activities.



Fresh Water vs. Salt Water


SALT WATER IN AN ESTUARY - Recent studies have indicated that most of the waterbodies in the U.S. no longer have their original full measure of biotic integrity. The best estimate so far, based on a "four star" system similar to that used for rating movies, is that most waterbodies in the U.S. would have "two or three stars" (not as good as they could be but still capable of supporting more than just tolerant forms of aquatic life). In Indiana, the largest river coming closest to a "four star" stream is the Tippecanoe River in the north central part of the State. The Tippecanoe still supports a wide variety of "intolerant" fish and mussel species. The river with the greatest water quality problems in Indiana is the Grand Calumet in Lake County. Until recently, it supported no fish at all (a true "zero star" river). The biggest challenges to restoring most other rivers and streams to "four star" status are reducing siltation and nutrient inputs, restoring a buffer of vegetation along streams, and reducing the frequency of straightening stream channels to hasten drainage.In collaboration with academic, governmental and private research institutions, the HBOI Aquaculture Division has designed and implemeted culture systems for a variety of marine animals and plants in a 15 acre complex adjacent to the Indian River Estuary. The facilities include several laboratories, hatcheries, nurseries, covered raceways, a 20,000 gallon environmentally controlled recirculation system and a total capacity of over 1,000,000 liters of saltwater culture systems.

Cordgrass' secret to success in the low marsh is its immunity to the harsh salt water that floods its roots twice daily. Salt is excreted through special glands, but Spartina has another defense from salt damage. The plant concentrates salt in its cells to levels higher than that of the surrounding seawater. As saltwater passes by, only the water is brought into the cell by osmosis, and the salt is left outside. No other species can survive these salty conditions as aptly as S. alterniflora, so it has little competition to deal with. Cordgrass can grow up to 3 meters in some areas of the marsh, but may only reach heights of less than 0.25 meters in others. S. alterniflora has a round, hollow, robust stem and large leaves that can be as wide as 1.3 centimeters. It is a perennial plant, and reproduces by spreading seeds, as well as through rhizomes.

S. alterniflora's major role as a food source begins after it is already dead and decomposed (see Decomposers and Consumers). As detritus, the cordgrass is dispersed to many other ecosystems, such as the beach and the estuary, and so provides nutrients to an area much larger than the one in which it grows. S. alterniflora also plays a very important role in the creation and maintenance of the salt marsh, its roots helping to keep the foundations of the growing marsh secure (see Formation of the Marsh). Finally, cordgrass even has a vital role in the maintenance of the beach ecosystem, as the plant's dead stems are often the foundation for the fragile sand dunes that are so important there.

Life in an Estuary


AQUATIC TOXICITY - One way scientists measure water quality is to collect samples of water, expose plants or animals to the samples, and see how well these test organisms survive, grow, and reproduce. If all of the various test organisms respond normally, the water is probably suitable for most forms of aquatic life. However, if the test organisms don't survive well or if they don't grow or reproduce normally, the water may contain a chemical which can cause problems in the environment. The scientist's job then is to figure out what the problem chemical is and how it can be reduced. Recent experience has shown that about half of all "wastewater discharges" in the United States (water used by cities or industries, cleaned up by pollution control technology, and discharged to freshwater streams) causes some degree of aquatic toxicity in lab tests. The most common pollutants causing toxicity in these tests include metals like copper and zinc, ammonia, pesticides (especially diazinon), and common salts like sodium chloride (freshwater organisms can't live very long in saltwater).


FISH & INVERTEBRATES IN STREAMS AND RIVERS - Another way to determine whether a waterbody is polluted is to examine the types and numbers of fish and invertebrates present. For example, a polluted river is known to support fewer kinds of animals than a clean river. Experienced biologists can even diagnose the type of pollution problem that may exist (e.g. sewage, nutrients, sediment, toxicity) by the telltale assembledge of species present in a waterbody. One very useful tool, used in various forms in the United States, is the "Index of Biotic Integrity " (IBI). This index is calculated by comparing the aquatic community of a given site to a "reference" site (one which has an environmental condition which is the best that could reasonably be expected to exist in a particular geographic area). Various ways of measuring "biotic integrity" (called metrics) are assigned numeric values. The values from all the metrics are added together to determine a site's IBI value. The higher the IBI value, the more "biotic integrity" the site exhibits. This techique takes into account more than just water quality. It also depends on other factors, such as how much the surrounding watershed has been altered.


BACTERIA - Pathogens are harmful microorganisms such as bacteria, parasites, and viruses that can be transmitted by water. One of the most commonly used ways to assess pathogen contamination in water is the "fecal coliform" bacterial assay. Fecal coliforms are a class of bacteria that live only in the intestinal tract of warmblooded animals. These types of bacteria are present in water only when it has been contaminated by fecal matter. The more fecal coliforms present in water, the greater the danger that a gastrointestinal disease may be transmitted (either by drinking the water or by incidental contact from swimming or wading). Fecal coliform bacteria can be fairly accurate indicators of other types of fecal pathogens as well (e.g. viruses, intestinal parasites, etc.).