Estuaries are bodies of water where rivers meet the sea or a large lake. Rivers spread out and slow when they meet the sea, creating unique conditions that are not found elsewhere. They provide homes for diverse wildlife, including popular fish species.



Estuaries: Nurseries of the Sea

Estuaries are often called the “nurseries of the sea” because so many marine animals reproduce and spend the early part of their lives there. As the tide rises and falls, water depth and chemistry change, creating a wide range of habitats. In some parts of estuaries, filtered by plants such as marsh and seagrasses, moving water becomes still, allowing mud and food particles to settle at the bottom. These variations create safe conditions, making estuaries ideal homes for plants and animals who feed, grow, or reproduce there. Estuaries are also a major stopover point for migratory animals such as waterfowl and salmon.

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Our bays, harbors, sounds, and other coastal estuaries include brackish or freshwater marshes, mangroves, seagrass beds, and salt marshes. You might also find oyster reefs, kelp forests, and rocky or soft shorelines—each populated with creatures that thrive in that setting. With so much variation, it’s no wonder that estuaries are among the most productive ecosystems on Earth.

Beautiful and Bountiful

Most of the fish and shellfish eaten in the United States—including salmon, herring, crabs, and oysters—spend some or all of their lifetime in estuaries.

Besides being an ideal home for fish and wildlife, estuaries are also a good habitat for people. Twenty-two of the 32 largest cities in the world are located on estuaries. Notable U.S. estuaries include Chesapeake Bay, New York Harbor, San Francisco Bay, Boston Harbor, Tampa Bay, and Puget Sound.

Each estuary displays unique beauty and attracts many visitors, who come to hunt and fish, watch birds, take photographs, hike, canoe and kayak, and observe wildlife. Our coastal communities rely on beautiful and bountiful estuaries for recreation, jobs, tourism, shipping, and fishing.

Ecosystem Services

Estuaries can filter out sediments and pollutants from rivers and streams before they flow into the ocean, providing cleaner water for humans and marine life. Healthy estuaries can absorb surges of water from storms, floods, and tides, protecting our homes and communities.

Economics of Estuaries

Estuary regions comprise only 13 percent of the land area of the continental United States, but they make up a disproportionate share of the national economy. These areas account for 43 percent of the population, 40 percent of employment, and 49 percent of economic output. In eight states, the estuary regions comprise 80 percent or more of the state’s economy. Because estuary regions contribute so much to our economy, the health of our estuaries concerns all of us. Did you know that:

More than 180 million Americans visit estuary and coastal waters each year for recreation and tourism.

Coastal tourism jobs are growing faster than other economic sectors.

Recreation provides up to 72 percent of the employment economy in coastal communities.

Restoring estuaries can provide economic benefits. One $3.5 million wetlands restoration project in California increased residential property values by $36.3 million.

Challenges for Estuaries

Estuaries are fragile ecosystems, vulnerable to both natural and man-made disturbances. The forces of nature—such as winds, tidal currents, waves, and temperature—can affect an estuary’s natural balance.

Human activities on land can harm estuary health in the water, often degrading living conditions for estuary residents and visitors. Stream and river banks can be damaged by erosion, outdated agricultural or forestry methods, or construction too close to the stream. Fish numbers then decline because their nesting and feeding areas are destroyed. Dams, invasive species, and poor boating and fishing habits cause even more damage.

Stormwater runoff from land carries a cocktail of contaminants from roads, vehicles, lawns, and construction and pours it into the nearest stream. Outdated farming methods can cause erosion, as well as nutrient and hazardous chemical pollution that ends up in the estuary. Urban waterways and large agricultural regions concentrate runoff and create toxic "hot spots" where nothing can live. For example, each year, the overload of agricultural chemicals causes a "dead zone" in the Gulf of Mexico spreading over 7,000 square miles, an area larger than the state of Connecticut.

In the past, it was considered good practice to fill wetlands, consequently shrinking the size of estuaries nationwide. Now that we know the value of estuary habitat, protecting and restoring it is a high priority.

What We Do

We Protect Estuaries

Estuaries protect our health and well-being by improving air and water quality; absorbing floods, tides, and storms; nurturing commercially important fish; and providing recreational and travel opportunities. It is our responsibility to protect estuaries from the many challenges they face. established the National Estuarine Research Reserves to protect these rich habitats and the species that live there. The reserves represent an important part of our commitment to coastal management. Under this partnership program, provides funding and guidance for the reserves, which are then managed by local stakeholders. The program currently protects more than 1.3 million acres of coastal wetland and helps states and territories prioritize conservation. Reserve staff work closely with local communities to keep coastal science current and relevant to them. By initiating the reserve process, we set conservation in motion, involving the people who will benefit most directly.

We Restore Estuaries

We restore habitat in estuaries across the country. While all estuaries share some qualities, each is a complex system with unique needs. The Estuary Restoration Act authorizes—working with partners in and out of government—to implement conservation projects. The act established an Estuary Habitat Restoration Council, which restores estuaries and their ecosystems and documents the resulting environmental and economic benefits.

Restoration Projects

Here are a few examples of our projects around the nation:

We replaced culverts up and down Connecticut’s Bride Brook, part of Long Island Sound estuary. With the increased flow from the new, larger culverts, fish could swim upstream for the first time in more than a decade. The 2017 spring run of migrating fish was almost five times what we had seen in the past.

In California, recent droughts have endangered the already struggling native salmon in the Sacramento and Feather rivers. By working cooperatively with the state wildlife agency, fish hatcheries have kept the fragile salmon population stable, releasing juvenile fish every year.

We Partner With State and Local Organizations teams with other federal agencies, such as the U.S. Environmental Protection Agency and the U.S. Fish and Wildlife Service, and provides grants that inspire state and local organizations to take action. We provide the science and planning expertise to help partners design and implement projects that reverse declining estuaries and restore their productivity.’s National Estuarine Research Reserves show how federal, state, and local organizations can partner successfully. By providing start-up funds and national guidance under the program, helps coastal states launch valuable conservation and research efforts, which are then sustained by a state agency or university.

What You Can Do 

Maintain your septic systems. Keep them in working order by pumping them every three years.

Pave less. Hard surfaces increase runoff, carrying pollutants into the watershed.

Obey no-wake zones. Waves damage shorelines and cause erosion.

Think before you pour. Many hazardous chemicals pass through our drains and treatment plants and end up in our waters. Buy biodegradable products.

Fish respectfully. Get the proper license, consider catch and release, and respect seasons and limits.

Create non-toxic pesticides. Soap and water work remarkably well and keep poisons out of our water.

Use native plants. They need less water and fertilizer to thrive.

Respect habitat. Treat the homes of sensitive marine life with respect—habitat and survival go hand in hand. When habitat disappears, so do plants and animals.

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Take action. Organize a stream, river, bay, or beach cleanup; get your local press to cover wetland stories; or invite an expert to speak at your school or community group.

Case Study: America"s Largest Estuary