ARTICLE

WHAT IS A SALTMARSH?

Updated on May 11, 2023

By Susan McLaughlin, public relations coordinator for the South Carolina Aquarium

Have you ever traveled to the coast, rolled down your windows and encountered a salty, sometimes sulfuric smell? Chances are, you’re surrounded by an incredible environment known as the saltmarsh.

south carolina saltmarsh

What makes a saltmarsh?

The saltmarsh is an ever-changing coastal environment that is heavily influenced by the tides. Along the East Coast, we experience semidiurnal tides, or two high tides and two low tides each day. There’s a constant ebb and flow of saltwater from the ocean mixing with freshwater from nearby rivers, creating what’s called a brackish water ecosystem. Because of its consistent changes — including salinity and water levels — the saltmarsh can be a harsh habitat to live in.

The first tell-tale sign you’re in the saltmarsh is the sight of long, flowing marsh cordgrass swaying in the breeze, its reflection sparkling in the shallow waters. Cordgrass is a hardy species that thrives in brackish water. It draws salt from the water and pushes small salt crystals out onto its leaves, giving each blade a gritty texture. The cordgrass has an extensive underground root system (called rhizomes) that can multiply and spread far and wide to produce new shoots in new locations.

The foundation of a saltmarsh is a substrate called pluff mud — a nutrient-dense mud that is slippery, squishy and a little stinky due to rich levels of minerals and biological material. This sulfuric and slightly sweet scent is what gives the saltmarsh that characteristic smell.

Pluff mud also works as a sponge. As the tides come in, the mud absorbs water, protecting the homes and habitats that lie beyond the saltmarsh from tidal flooding. Pluff mud is a critical source of nutrition for those microorganisms that inhabit the saltmarsh and create the beginning of the food web that so many other species depend on.

Animals within a saltmarsh

Embedded in the pluff mud are oysters, a keystone species that holds the sediment and the entire ecosystem together. They continually grow and build upon each other to form oyster reefs. Oysters are filter feeders; as they feed, they clean the surrounding water by filtering out tiny particles of bacteria, algae and sediment. A single adult oyster can filter four gallons of water per hour! Oyster reefs keep the water clean and healthy, protect shorelines from erosion and provide an excellent food source for both saltmarsh inhabitants and humans.

saltmarsh oysters

Along with oysters, the saltmarsh provides a unique shelter for other species and acts as a nursery for their young. Many species of fish will lay eggs in the saltmarsh, and the young will grow there where they are protected from larger predators. Not only do fish, crustaceans, worms and snails find protection here, but even animals like bottlenose dolphins will bring their calves into these safe spaces.

It’s not just aquatic animals that call the saltmarsh home — shorebirds also take advantage of this area. Most are wading species with tall skinny legs, perfect for standing in the water without getting their feet stuck in the pluff mud. You might see herons, egrets or even larger birds like wood storks, pelicans or roseate spoonbills. These wading birds will often hunt at low tide, the perfect time to catch all the fish and invertebrates that followed the flooding and high tide in and are now more densely packed together in the shallow water that remains.

saltmarsh spoonbill

We can’t forget about reptiles, too! Diamondback terrapins are one of the only species of turtle that live in brackish water. You can find them wading, sunning and even moving to higher ground within the saltmarsh to lay their eggs. Occasionally, juvenile sea turtles like the Kemp’s ridley and green will seek refuge in a saltmarsh to snack on seaweed and small shrimp.

saltmarsh terrapin

Our relationship with the saltmarsh

While saltmarshes are vital to the lives of countless plant and animal species, they are just as indispensable and inseparable to humans. Saltmarsh habitats exist along every coast of the United States and comprise a significant portion of­ the coastline of South Carolina, covering nearly half a million acres. This expansive environment provides crucial protection for those living in the Lowcountry, or region situated at sea level in South Carolina.

With sea levels rising, and storms increasing in frequency and strength, our coastline is vulnerable to flooding and erosion. However, the saltmarsh provides a buffer for storms to dissipate over, as well as a holding space for extra water.

The health of the saltmarsh and the animals living there is directly connected to our own. Seventy-five percent of the food we harvest from the ocean once spent part of its life in the saltmarsh. But if you have spent your time on the edge of that warm dock, or love that distinctive smell, you’ll know that the saltmarsh is connected to more than just our physical health. We spend our time in saltmarshes for many types of recreation, from fishing and birdwatching to kayaking and paddle boarding. Spending time in nature has a powerful impact on our well-being, something that the saltmarsh teaches you each time you visit.

See the saltmarsh at the South Carolina Aquarium

Located in downtown Charleston, the South Carolina Aquarium has an open-air saltmarsh exhibit that overlooks the water. It’s designed to give the illusion of floating through the saltmarsh on a small kayak, with the extra vantage points to peek into the waters below. Small fish swim through the water beside diamondback terrapins, and above, many species of birds wade and fly.

kayaks on saltmarsh

The Aquarium does extensive conservation work in the saltmarsh habitats of South Carolina, such as litter sweeps, saltmarsh planting and oyster reef restoration. However, saltmarshes are at risk due to habitat destruction and pollution. The saltmarsh is easily susceptible to collecting larger plastic debris in the grasses that filter the flowing water, and the mud and oysters can accumulate microplastics and chemical or sewage pollution.

The saltmarsh habitat is an invaluable resource for humans and animals alike. While the saltmarsh continues to provide for us, we can return the favor by being mindful of our waste, the chemicals we use and the choices that we make that impact the environment. When we protect the saltmarsh, the saltmarsh protects us in return.

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