Exploring New Places: South Carolina's Salt Marshes and Tidal Creeks

Throughout South Carolina's Low Country, winding tendrils of water wend their way through a sea of grass, rising and falling with each new tide.  Low-lying intertidal areas immediately inland from the coast, salt marshes and tidal creeks form the interface between upland forests and urban areas, and brackish estuaries where freshwater and saltwater mix.  

Tidal creeks are, to a first-time visitor to the South Carolina coast like myself, absolutely beautiful, mysterious, enthralling places where silvery ribbons of water meander seemingly aimlessly through a vivid green matrix.  They give the impression that there is water everywhere, a foreign concept to someone from arid, drought-stricken Mediterranean California.  And that was my first impression of South Carolina: there was water everywhere I looked!  Water in the ocean, lakes, rivers, creeks and wetlands, water covering the ground, falling from the sky, in the air itself!  Is there any land at all in this veritable water world?!  

Undoubtedly the best view of this network of rivers and creeks is from the air, where I had my first glimpse of the Low Country as we began our decent into the Charleston airport.  But alas, I was too busy trying not to be airsick (again) to take a photo from the plane.  The picture below, from a Smithsonian article, is the best example I could find.

NOT my photo, but similar to the view we had from the airplane before landing in Charleston. 
South Carolina Low Country's tidal creeks from the air.  Photo accessed from Smithsonianmag.com.

Venturing out into the salt marshes (for indeed there is dry ground here!), I immediately began to recognize the beauty, significance, and fragile nature of these hugely productive ecosystems.  I also noted at once the similarities between South Carolina's salt marshes dominated by smooth cord grass (Spartina) and California's own coastal marshes of pickleweed.

Salt marshes are intrinsically linked to the twice-daily cycle of flooding and draining by the tides.  This rapid and frequent fluctuation of micro-habitat, as the marsh swings wildly from dry to wet, hot to cold, freshwater to saltwater twice each day adds yet another challenge to an already difficult place to live.  In order to survive and thrive in these conditions, species must be highly specialized and equipped to deal with their ever-changing conditions.  Life in the intertidal zone the world over is exceedingly difficult!  

Creatures inhabiting the mud of salt marshes must be able to withstand alternating periods of
inundation and desiccation.  

Even so, salt marshes are one of the most productive ecosystems found anywhere on earth.  Abundant sunlight and soil extremely rich in decomposing organic matter allow the specialized organisms that do live here to absolutely thrive and develop extensive populations. 

Fiddler Crabs

Smooth cord grass, often called by its generic name Spartina, is the dominant plant of South Carolina's salt marsh.  The substrate in which it grows is known as "pluff mud" (so named for the sound it makes while sucking your shoes off, or so we were told), and is extremely rich in organic matter.  (So much so that slaves working on nearby cotton plantations were made to gather the mud by the barrow full and spread it on the fields to boost productivity.) 

A Tri-colored Heron making its way through the sticky pluff mud

This sticky marsh muck prevents large herbivores from grazing on the grass, allowing the bulk of it to die back in the fall and decompose, thus adding to the organically rich substrate that forms the basis of the food web.  Algae feeds on the dead and decomposing plant matter, while fiddler crabs and snails shred plant material, speeding the decomposition process.  Filter feeders, like oysters and mussels, filter particles from the water. 

A Wood Stork wades through an oyster reef - a critically valuable habitat in itself - at low tide.

Reptiles are few in tidal wetlands, but the diamond back terrapin, a turtle, forages here.  Birds, however, are plentiful, taking advantage of the abundance of fish and invertebrates like shrimp, crab and shellfish.  While herons, egrets and ibises in stunning variety feed on invertebrates in the shallows, osprey and terns dive for fish in deeper water.  Although many species forage here, only two birds nest in the tidal salt marshes: the Clapper Rail and the Marsh Wren, both of which are often heard but seldom seen.  

Tri-colored Heron in the shallows

As may be expected, salt marshes are attractive to an astounding variety of wading birds, particularly conspicuous birds like herons, egrets and ibises - far more than are found in California!  In addition to the familiar Snowy Egret, Great Egret, Great Blue Heron, Green Heron and Black-crowned Night Heron, I made the acquaintance of several new species as well: the Tri-colored Heron, Little Blue Heron and Yellow-crowned Night Heron; the Wood Stork (North America's only species of stork); and the Glossy Ibis and White Ibis.  Present but elusive (at least to me) are also Roseate Spoonbills, Least Bitterns and an occasional Reddish Egret.

A flock of Wood Storks gathers at Huntington Beach State Park

With a half-million acres of salt marsh and tidal creeks, South Carolina boasts more of this coastal habitat than any other Atlantic state.  And as always, with great power - that is, a great amount of natural resources - comes the great responsibility of protecting it.

A Yellow-crowned Night-heron amidst the cord grass along Charleston Harbor

Due to their location along prime coastal real estate, the tidal salt marshes of South Carolina (as well as California and the world over) sustained serious losses in the decades before their value was realized.  Over half of the salt marsh habitats in the United States have been drained and filled for building homes and developing industry and agriculture.  Here is, unfortunately, something California's pickleweed salt marshes have in common with the cord grass marshes of the Atlantic states.  Thankfully, scientists have begun to realize the value of these unique ecosystems, and efforts are being made across the country to preserve and restore salt marshes.

A boardwalk to a shaded pavilion allows visitors to access the marsh at Huntington Beach State Park to
contemplate its tranquil beauty and ecological value.

Like other wetlands, the value of salt marshes and tidal creeks might not be immediately apparent to the casual observer (or greedy developer).  But the ecosystem services they provide for us fall into five major categories.

Salt marshes and tidal creeks act as:

- Nurseries for a wide variety of fish and shellfish species that we harvest for food (which contributes directly to the economy)

- Filters to clean and absorb sediments and toxins from the water

- Buffers which shelter the mainland from erosion by absorbing the bulk of storm surges

- "Sinks" to sequester or store carbon

- Places of great beauty and recreational value (which also contributes to the economy)

A peaceful scene: a summer evening in the marsh

Perhaps surprisingly, salt marshes are critical to South Carolina's economy, as three-quarters of all species harvested as seafood from South Carolina's waters, including offshore species, depend on salt marshes for at least part of their life cycle.  Even some species associated with the open ocean spend at least part of their lives in the calm estuarine waters.  Several types of animals we enjoy at our tables, such as clams, oysters, shrimp and crab, all depend on healthy salt marshes for reproduction.  

A Tri-colored Heron beside an empty clam shell

In addition to a nursery, the marsh is also nature's great filtration system, working hard to vastly improve water quality.  The dense plant roots and highly organic substrate filter silt and toxins out of water that runs off the mainland, which is often heavily laden with excess nutrients, chemicals and pollutants.  As water moves slowly through the wetland, toxin-laden sediments drop out of the water and become incorporated into the substrate before they can enter the open water and the nurseries of fish and shellfish that we harvest and consume.

This salt marsh in Mount Pleasant serves to filter water before it enters Charleston Harbor and the Atlantic beyond.

Critically for those living along the coast, tidal salt marshes act as a buffer against powerful storm surges that would otherwise erode the coastline and flood homes.  The coastal salt marsh acts like a giant sponge, absorbing sudden influxes of water, slowing strong surges of water, and greatly reducing flood damage to coastal property.  

Residents like these on Sullivan's Island may not realize it, but intact salt marshes create buffers between their homes
and powerful storm surges.

In light of climate change, which has certainly been spurred along by humans and our excess production of greenhouse gases (a heavy topic for another day), wetlands are invaluable as blue carbon sinks.  (Blue carbon is the term given to carbon sequestered by oceans and coastal ecosystems.)  Abundant wetland plants take up carbon dioxide from the atmosphere through the process of photosynthesis, storing the carbon in dead and living plant material as well as in the mud.  Coastal habitats like salt marshes sequester even more carbon than terrestrial forests. 

Massive amounts of "blue carbon" are stored in these marsh plants, while even more is sequestered below in a thick
layer of mud.

Fishing, boating, kayaking, swimming and stand-up paddle boarding are all recreational activities we saw locals and tourists alike enjoying in and around the salt marshes near Charleston.  Additionally, there are plenty of places to access salt marshes from the shore and boardwalks for a morning jog, evening yoga session, birding venture or contemplative stroll through a beautiful natural habitat.

This beautiful recreational pathway leads from a quiet Mount Pleasant neighborhood out into the salt marsh. 
We loved this walk, and were pleased to see so many locals enjoying the area, strolling, biking, jogging, walking dogs,
even practicing yoga on the lawn!  On either side were people swimming, fishing, boating and cruising on
stand-up paddle boards through the marsh.

For more - much more - information about South Carolina's salt marshes and tidal creeks, I highly recommend reading this free Guide to the Salt Marshes and Tidal Creeks of the Southeastern United States, written by researchers at South Carolina's Department of Natural Resources with help from the South Carolina Sea Grant Consortium and Clemson Extension, and funded by the U.S. Environmental Protection Agency.  

A Green Heron stalks the shallows

And, as always, I recommend exploring these beautiful places for yourself!  

In South Carolina, check out:

Huntington Beach State Park

Cape Romain National Wildlife Refuge

ACE Basin

During the 1700's, the boardwalk at Pickett Park in Mount Pleasant was a plank footbridge spanning the inlet
separating Mount Pleasant from Sullivan's Island.  It became a vehicle bridge in the 1920's, but today only a portion
of the bridge remains as a recreational path for pedestrians.

Where the boardwalk ends... the wild marsh begins!