THE SALT MARSH

The 3000-acre salt marsh located on the west or land-ward side of Hunting Island is a vast nursery for juvenile fish. Three-quarters of the seafood we eat has its start in the salt marsh. The salt marsh is also an important stopover for migrating birds and a banquet for many year-round residents. That is part of the reason that Hunting Island and the other barrier islands are designated by the Audubon Society to be Important Birding Areas (IBA). 

 

A system of tidal creeks interlaces the marshes, transporting nutrients and living organisms with every tide change. The sheer quantity of nutrients in the salt marsh makes it one of the most productive habitats on earth. In addition, the salt marsh is an important carbon sink that protects coastlines from erosion and storms.

 

Salt marshes are unique ecosystems at the interface of marine and terrestrial ecosystems. They are tidal—experiencing high and low tides like the ocean. At high tide, a wide variety of creatures live in the nutrient “soup” of the salt marsh that is made from the decomposition of the grasses. These include dolphins, tiger sharks, mullets, shrimp, and crabs. Ospreys and eagles soar above hunting their prey. At low tide wading birds like egrets, ibises, and herons are seen fishing here. Raccoons may pad through the pluff mud to dine on shrimp or crab.

 

As an intertidal zone, the conditions in the salt marsh are constantly changing. The highest points in the marsh are often areas of lowest salinity because of rain and runoff, while the lowest points are higher in salinity. Therefore, the salt marshes are continually fluctuating between wet and dry, saline and fresh. 

 

Pluff (or plough) mud of the salt marsh is famous for its smell of decomposing detritus at low tide. Like the nutrient soup that covers it twice a day, the mud is rich in decomposing grasses, particularly spartina grass. The pluff mud is so gooey that ruminant animals such as deer or cattle, usually know that if they step in it, they will be stuck. That protects the grasses from being grazed.

 

As the grasses mature and decay, they become important attachment sites for microscopic organisms that further break down the grass so that it becomes edible by animals. Fiddler crabs and marsh periwinkles shred the plant matter. Oysters and mussels filter particles from the water. The diamondback terrapin lives in the salt marsh, traveling between high tide for foraging and high ground for nesting.  Although alligators may travel through the salt marsh, they prefer less-saline ecosystems.

 

South Carolina, North Carolina, and Georgia have two-thirds of the salt marshes in the US. Fifty percent of South Carolina’s salt marsh is in Beaufort County.

Spartina by any other name

 

Spartina, commonly known as cordgrass, is the most abundant marsh grass surrounding Hunting Island. However, in 2019, phylogenetic studies discovered that this most common grass in the salt marsh—Spartina alterniflora—had been misnamed. It is more appropriately placed in the genus Sporobolus. That change eliminates the genus Spartina completely and renames the beloved Lowcountry grass Sporobolus alterniflorus, much to local disgruntlement. 

 

This most common salt marsh plant, however it is named, tolerates saltwater incursion twice a day. In the summer spartina gives the salt marsh a bright green hue. It produces small white flowers in the fall which become seeds. When spartina grass dies in the winter it breaks off and floats away, becoming wrack, the brown stalks that create the wrack line on the beach at high tide. Piles of wrack on the beach can help build new sand dunes as wind and waves move sand that is caught by the dead grass stalks. 

 

Photo courtesy of Andy Stephens

 

"Oscar"

Photo courtesy of Andy Stephens

 

Photo courtesy of Linda Sigfoos

 

"Herons over the salt marsh and spartina grass in fall colors." Photographer: Gary Jones

BARRIER ISLAND STORY ECOLOGY

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