Estuary Habitat

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Estuaries: Nurseries of the Sea

Estuaries are often called the "nurseries of the sea," because so many animals reproduce and spend the early part of their lives there. Salty seawater mixes with fresh water draining from the land to create habitats with unique conditions that are not found elsewhere.

As the tide rises and falls, water depth and chemistry change, creating a wide range of habitats. In some parts of estuaries, moving water becomes still, allowing mud and food particles to settle at the bottom. These safe conditions make estuaries ideal homes for the plants and animals who feed, grow, and reproduce there. 

Bays, harbors, sounds, and other estuaries include habitats like marshes, mangroves, and seagrass beds. You might also find oyster reefs, kelp forests, and rocky or soft shorelines. Each of these habitats are 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.

Benefits of Estuaries

Estuaries provide important benefits—called ecosystem services—that impact our day-to-day lives. In addition to their natural beauty, they support clean water, abundant wildlife, and recreation. They also protect homes, businesses, and infrastructure from the impacts of flooding and storms. 

Sustainable Fisheries

Most of the fish and shellfish eaten in the United States—including salmon, herring, crabs, and oysters—spend some or all of their life in estuaries. Estuaries provide habitat for about 68 percent of the U.S. commercial fish catch and 80 percent of recreational catch. Estuaries are also a major stopover point for migratory animals such as waterfowl.

Cleaner Water

Estuaries can filter out sediments and pollutants from rivers and streams before they flow into the ocean. As water runs off the land, plants such as marsh vegetation and seagrasses absorb and filter out pollution. This provides cleaner water for humans and marine life. 

Flood and Storm Protection

Estuaries play an important role in protecting communities from the impacts of flooding and extreme weather. Salt marshes and seagrass beds serve as natural infrastructure that can protect coastal communities from flooding and erosion. Marshes, mangroves, and seagrass beds can help capture and store carbon from greenhouse gases—like carbon dioxide—from the atmosphere. This type of carbon is known as coastal blue carbon. 

Tourism and Recreation

Each estuary displays unique beauty and attracts many visitors. Tourists and residents visit estuaries to hunt and fish, watch birds, take photographs, hike, canoe and kayak, and observe wildlife. 

Tourism and recreation in coastal areas like estuaries contribute approximately $143 billion to the national economy each year. Ocean-based tourism and recreation industries employ nearly 2.5 million people. Coastal tourism jobs are also growing steadily, at a slightly higher rate than other economic sectors. 

Jobs and Economic Benefits

Besides being an ideal home for fish and wildlife, estuaries are good habitats for people. Coastal economies rely on estuaries for jobs, shipping, and commercial fishing. They also boost property values and attract tourism in local communities (PDF, 4 pages). 

With the amount of benefits these regions provide, it’s no surprise that 22 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.

Estuary regions comprise only 13 percent of the land area of the continental United States, but they are some of the most economically valuable areas in the country. These areas account for 40 percent of the population, 39 percent of employment, and 47 percent of economic output. In eight states, the estuary regions comprise 80 percent or more of the state’s economy. 

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Challenges for Estuaries

Estuaries are fragile ecosystems, vulnerable to both natural and human-made disturbances. 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, degrading living conditions for species that live in or visit estuaries. 

Habitat Loss

Because they are situated where rivers meet the sea, estuaries are sensitive to changes occurring both in the ocean and on land. For example, rising sea levels can inundate shallow coastal areas with seawater, disrupting the balance between fresh and salty water. Floods, storms, and other extreme weather events can change the amount of water flowing into an estuary from upstream, leading to more polluted runoff, erosion, and sedimentation. 

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 can cause even more damage.

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. 

Polluted Runoff

Stormwater runoff carries contaminants from roads, vehicles, lawns, and construction from the land and pours it into the nearest stream. Outdated farming methods can also cause excess nutrients, sediment, and chemical pollution to end up in estuaries. 

Urban waterways and large agricultural regions concentrate runoff and create toxic "hot spots" where nothing can live. For example, each year, an overload of polluted runoff causes a "dead zone" in the Gulf of America spreading over 6,000 square miles—an area larger than the state of Connecticut.

What We Do

We Protect Estuaries

NOAA 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, NOAA 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

The Office of Habitat Conservation’s NOAA Restoration Center provides funding and technical assistance to habitat restoration projects across the country, including in many estuaries. These projects support sustainable fisheries, help recover threatened and endangered species, and increase the resilience of coastal communities. 

Examples of our restoration work include:

• Removing a dike and other barriers to restore the natural flow of tides to Herring River estuary in Massachusetts. The work will allow river herring, whose populations dropped by 90 percent in the decades after the dike's construction, to return and spawn in greater numbers.
• Removing old levees, fill, and tide gates to create tidal estuary habitat in Oregon’s Tillamook Bay. The landscape-scale Southern Flow Corridor project revitalized wetlands for threatened salmon and reduced flooding in the surrounding communities and farmlands.
• Rebuilding barrier islands and marshes in Louisiana’s Barataria Bay. By building or enhancing almost 3,000 acres of habitat in the area, NOAA and partners have helped to slow land loss, defend coastal communities from storms and flooding, and support a variety of fisheries and wildlife.

Restoring estuaries can provide economic benefits. For example, a $3.5 million NOAA-supported wetland restoration project in California increased residential property values by $36.3 million.

We Partner to Support Estuaries 

NOAA 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 also provide technical support to help partners design and implement projects that protect and restore declining estuaries.

NOAA’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, NOAA helps coastal states launch valuable conservation and research efforts, which are then sustained by a state agency or university.

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Case Study: America's Largest Estuary

What You Can Do 

• 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.
• Volunteer. Organize a stream, river, bay, or beach cleanup, or invite an expert to speak at your school or community group.
• Launch a restoration project in your community. Resources like the Coastal Restoration Toolkit can help you find tools and information for starting a habitat restoration project in your area.
• 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.
• Use non-toxic pesticides. Soap and water work remarkably well and keep toxins out of our water.
• Maintain your septic systems. Keep them in working order by pumping them every three years.
• Pave less. Hard surfaces increase runoff, carrying pollutants into nearby waterways.
• Obey no-wake zones. Waves damage shorelines and cause erosion.
• Choose native plants. They need less water and fertilizer to thrive.