Estuaries: Why These Coastal Ecosystems Matter | National Estuaries Week

Estuaries: Where Rivers Meet the Sea and Life Thrives

Where freshwater meets saltwater, something remarkable happens.

Estuaries are places of constant change—where rivers and streams meet the ocean, tides move in and out, and freshwater mixes with seawater. These dynamic coastal ecosystems may look peaceful from the surface, but beneath the water is a remarkably productive environment that supports wildlife, communities, economies, and the health of our oceans.

From Florida’s Indian River Lagoon to Chesapeake Bay and San Francisco Bay, estuaries are among the most important ecosystems on Earth. Yet they are also among the most threatened.

This National Estuaries Week, September 20–27, 2026, take a closer look at these incredible places and discover why protecting estuaries means protecting the future of our coasts.

What Is an Estuary?

An estuary is a partially enclosed coastal body of water where freshwater flowing from rivers and streams mixes with saltwater from the ocean. The result is often brackish water, with salinity that falls somewhere between freshwater and seawater.

But an estuary is more than just a place where two types of water meet. It is a complex ecosystem made up of interconnected habitats, including:

• Seagrass meadows

• Mangrove forests

• Salt marshes

• Oyster reefs

• Mudflats

• Tidal creeks

• Coastal wetlands

• Shallow bays and lagoons

Each habitat provides food, shelter, nursery grounds, or other essential resources for wildlife.

Because conditions in an estuary are constantly changing with tides, rainfall, river flow, temperature, and salinity, the animals and plants that live there have developed remarkable adaptations for survival.

Why Are Estuaries So Important?

1. Estuaries Are the “Nurseries of the Sea”

One of the most important things estuaries do is provide protected habitat for young marine animals.

Compared with the open ocean, estuaries often offer shallow, calmer waters and abundant food. Seagrass beds, oyster reefs, mangroves, and marshes provide places where juvenile fish and other animals can hide from predators, find food, grow, and eventually move into other marine habitats.

This is why estuaries are often called the “nurseries of the sea.”

NOAA notes that more than 75% of fish and shellfish harvested in the United States depend on estuarine habitats at some point in their lives.

That means the health of an estuary can have a direct connection to the fish and seafood people enjoy miles away from the coast.

2. Estuaries Help Keep Our Water Clean

Think of an estuary as a natural water-treatment system.

Water flowing from land carries nutrients, sediments, and sometimes pollutants toward the coast. Wetlands, seagrasses, marshes, mangroves, and other estuarine habitats can capture sediments and absorb or transform nutrients and pollutants before they reach the open ocean.

Estuarine wetlands can act as natural filters, helping remove excess nutrients and other contaminants from water moving through the ecosystem.

But there is an important catch: estuaries can only absorb so much.

When too much pollution, sediment, or excess nutrients enter an estuary, the ecosystem can become overwhelmed. Excess nutrients, for example, can contribute to harmful algal blooms, low oxygen conditions, and habitat loss.

Protecting an estuary therefore starts well beyond the shoreline. What happens throughout a watershed can eventually affect the estuary at its mouth.

3. Estuaries Protect Coastal Communities

Estuaries aren't just important for wildlife—they can also help protect people.

Wetlands, marshes, mangroves, seagrasses, and other coastal habitats can absorb wave energy, slow storm-driven water, reduce erosion, and help buffer coastal communities from flooding.

In other words, healthy coastal ecosystems can serve as a natural line of defense between land and the sea.

For coastal communities like those found throughout Florida, these natural protections can be incredibly valuable.

4. Estuaries Support Jobs and Recreation

Estuaries are also economic engines.

Fishing, boating, kayaking, birding, tourism, shipping, and other recreational and commercial activities depend on healthy coastal waters. Estuaries also provide habitat for many species that support recreational and commercial fisheries.

Across the United States, millions of people live near estuaries and depend on the environmental and economic benefits they provide.

So when we protect an estuary, we're not simply protecting a body of water. We're helping protect the communities, businesses, wildlife, and recreational opportunities connected to it.

Little-Known Facts About Estuaries

Think you know estuaries? Here are a few facts that may surprise you.

Estuaries are some of the most productive ecosystems on Earth.

The combination of sunlight, nutrients, shallow water, and abundant plant life makes estuaries exceptionally productive ecosystems. In fact, estuaries can produce more organic matter than similarly sized areas of forests, grasslands, or agricultural land.

Estuaries aren't just for fish.

Birds, reptiles, mammals, invertebrates, and countless other organisms depend on estuarine habitats. Some species live in estuaries their entire lives, while others use them for only part of their life cycle.

Migratory birds, for example, can use estuaries as important places to rest and refuel during long journeys.

Estuaries can help fight climate change.

Mangroves, salt marshes, and seagrass beds can capture carbon dioxide and store carbon in their plants, roots, and sediments. This coastal “blue carbon” makes estuarine habitats an important part of climate resilience and conservation efforts.

Some of the world's biggest cities are connected to estuaries.

Estuaries have historically been attractive places for human communities because they provide access to transportation, food, natural resources, and sheltered waters. NOAA notes that 22 of the world's 32 largest cities are located on estuaries.

Oyster reefs are more than a seafood source.

Oysters are ecosystem engineers. Oyster reefs create three-dimensional habitat that can provide shelter for other organisms while also helping filter water and stabilize portions of the estuarine environment.

Not every estuary is saltwater.

While we typically think of estuaries as places where freshwater rivers meet the ocean, freshwater systems with many similar characteristics can also occur where rivers meet large lakes, such as the Great Lakes.

Florida's Estuaries: A Coastal Treasure

Florida is surrounded by water, but the importance of its estuaries goes far beyond the shoreline.

The state's estuaries—including the Indian River Lagoon, St. Lucie River, Tampa Bay, Charlotte Harbor, Biscayne Bay, and Florida Bay—support an extraordinary variety of habitats and wildlife.

For Florida's coastal communities, estuaries are part of everyday life. They influence fishing, boating, tourism, wildlife, water quality, recreation, and the overall health of the coastal environment.

The Indian River Lagoon, for example, is not simply a scenic waterway. It is an interconnected estuarine system where freshwater, saltwater, wildlife, seagrasses, wetlands, mangroves, and human communities all interact.

That interconnectedness is also what makes estuaries vulnerable.

What happens upstream can eventually make its way downstream.

Stormwater runoff, excess nutrients, sediment, habitat destruction, changes in freshwater flow, pollution, and other pressures can all affect estuarine health.

Why National Estuaries Week Matters

National Estuaries Week is an opportunity to stop and recognize something that can be easy to overlook: healthy estuaries are essential to healthy coastal communities and healthy oceans.

National Estuaries Day began in 1988 as a way to raise awareness about the importance of estuaries and the need to protect them. Today, National Estuaries Week provides an opportunity for people across the country to learn about these ecosystems and participate in activities that support their protection.

But awareness is only the beginning.

National Estuaries Week is a reminder that everyone has a connection to an estuary—even if they don't live directly on the water.

The water that flows down a street can eventually enter a storm drain. Rain can carry nutrients and pollutants from yards and roads into local waterways. Those waterways connect to larger rivers, lagoons, bays, and eventually the ocean.

Our watersheds connect us to our estuaries.

How Can You Celebrate National Estuaries Week?

You don't have to be a scientist to make a difference.

During National Estuaries Week, consider:

• Visit an estuary. Explore a local lagoon, bay, river, marsh, or coastal wetland.

• Get on the water. Kayaking, paddleboarding, boating, and fishing can provide a different perspective on estuarine habitats.

• Go wildlife watching. Look for fish, birds, dolphins, manatees, turtles, crabs, and other animals that depend on coastal ecosystems.

• Learn about your watershed. Find out where the water from your neighborhood ultimately flows.

• Reduce runoff. Use fertilizer responsibly and avoid allowing pollutants or trash to enter storm drains.

• Support habitat restoration. Seagrass, mangrove, oyster reef, and wetland restoration projects can help rebuild important estuarine habitats.

• Participate in citizen science. Community monitoring programs provide valuable information about changing environmental conditions.

• Share what you learn. Talk with friends and family about why estuaries matter.

Small actions can add up when entire communities participate.

The Future of Our Estuaries Depends on Us

Estuaries are places of transition, but they are also places of connection.

They connect rivers to the ocean.
They connect land to water.
They connect wildlife to habitat.
And they connect human communities to the natural systems that sustain them.

Their health is closely tied to the health of our rivers, wetlands, seagrass meadows, mangroves, beaches, and oceans.

This National Estuaries Week, take a moment to look at the water around you and consider where it came from—and where it is going.

Because protecting our estuaries isn't just about protecting a place.

It's about protecting the life, communities, and future connected to it.

Celebrate National Estuaries Week

National Estuaries Week takes place September 20–27, 2026. Find a local estuary, learn something new, get involved in conservation, and share why these remarkable ecosystems matter.

Our estuaries need advocates—and every one of us can play a role.