A do-it-yourself tour of a southern marsh ecosystem

saltwater marsh

SUMMARY The saltwater marsh, such as that found along the coast of Georgia and South Carolina, is the most valuable land in the world for the common good of man. Georgia and South Carolina together have about 50 percent of the salt marsh on the east coast. This Do-It-Yourself Tour gives you an up-close look at this amazing resource.

Seemingly barren expanses of grass and mud, at first glance the salltwater marshes appear like wastelands. Look again. The grass fields like those along the Georgia Coast give untold benefits to nature and man. Each acre can produce 20 tons of plant matter annually, far more prolific than any agricultural rival.

This biological factory feeds and shelters young shrimp, mollusks, crustaceans, and fish; 75 percent of commercial seafood species spend part of their lives in the marshes. Marshes do much for humans, purifying sewage better and cheaper than any man-made facility and generating 20 percent of the world’s oxygen.

Besides utility, marshes exhibit considerable natural elegance. Black needle rush, a highly adaptable short grass with sharp tube-like leaves, dominates in the bay marshes. Smooth cordgrass, a broad-bladed plant up to three-feet high, clings to the outer, drier edges of the bay. And ripcord, a common grass in Georgia coastal marshes, lives only on the inner, wetter edge.

Underfoot, rich black mud grasps and pulls at the boots of the unwary. The odor announces anaerobic bacteria, which emit hydrogen sulfide when they digest organic material. No one sinks much further than a knee. Firm ground is several feet below.

Birds feed and nest. Oysters proliferate, as do hermit crabs and periwinkle snails, which slide up and down cordgrass stalks feeding on microscopic protozoa. Stuffing themselves with nutrient-rich mud, herds of fiddler crabs race to tiny burrows if threatened, their collective stampede sounding like soda pop fizz. The males linger, waving their dominant claw in displays of bravado.

Latham’s Hammock off the Jekyll Island causeway is a good place to view and tour a marsh; and other locations are included in the Marsh Tour map. It’s best to visit marshes at low tide when more is exposed.

Marsh Tour Latham’s Hammock is the first large island on the left (south) of the causeway leaving Jekyll Island and is one mile from the drawbridge. Entering from the Jekyll Island side of the hammock, one crosses a high, dry marsh and salt “pans.” This sandy soil provides easy walking almost completely around the hammock and allows access to many environments bordering the island. At any point, the walk from the hammock into the marsh demonstrates the transition from dry marsh communities to wet marsh communities.

When first standing at the edge of a saltwater marsh, many people are impressed by its vastness and think of it as a sea of grass or an expanse of wasteland. Unfortunately, this last concept has led people to look upon the marshes as a realm to be conquered, tamed and made “useful” to man. The salt marsh, such as that to be found on the Georgia coast, is the most valuable land in the world to the common good of man.

Aside from its aesthetic value, it is valuable in three different aspects. First, the salt marsh is the most productive of any known ecosystem. A healthy marsh can produce as much as 20 tons of dry matter per acre per year and thus provide food for infant shrimp, oysters, clams and the young of many species of fish. The marsh is also important as an oxygen generator. It is estimated that 20 percent of the oxygen in the air is produced by this valuable zone. A third, little recognized value is the marsh’s water purification function. Waste waters from cities are usually given primary and secondary treatment. The third level of treatment is so expensive that it is usually not done except by the natural marshes.

Evidence substantiates that the salt marsh is worth $83,000 per acre per year to the common good of people. Georgia has about one-third of the salt marsh on the east coast; and Georgia and South Carolina together have about 50 percent of the salt marsh on the east coast.

The tall, broad bladed grass that dominates the marsh is smooth cordgrass (Spartina alterniflora). It has a thick stalk almost one-half inch in diameter and long, tapering leaf blades that can grow 10 feet tall. This is the great producer of the salt marsh. The plants of the marsh sort themselves into zones, depending on their adaptation to the frequency of tidal water supplies. Cordgrass occupies the lower level that receives water and minerals twice daily as the tide comes in.

At just a little higher elevation, zones of glasswort grow. This has a green-to-pink, thick, fleshy stem and virtually microscopic leaves. The little stems are edible and have a crunchy, salty taste.

At an elevation half an inch higher than glasswort is Juncus roemarianus, the black rush of brackish habitat. It is a slow growing plant with tube-like leaves, which receives tidal water and minerals monthly when the spring tide comes in. Its pointed leaves are as sharp as needles.

The strong odor of the marsh is caused by the richness of the marsh mud. Since the marsh is regularly covered with tidal water, the organic material in the mud can only be decomposed by anaerobic bacteria, that is, bacteria that take their oxygen from water. Part of the odor of the marshes is hydrogen sulfide produced as a by-product of these types of bacteria.

The blue-green algae, which grow at the base of a cordgrass stalk, also contributes to the strong marsh smell. This primitive plant has the vital ability to change atmospheric nitrogen into forms that cordgrass and other plants can.

Of course, there are animals in the salt marsh, too. A whole host of migrant birds, such as the ring-billed gull, feed in the marshes as transients. Perhaps more spectacular are the permanent residents like the clapper rail or marsh hen (right). These little game birds find plenty of food in the rich marsh mud.

By far, the most numerous marsh animals are the fiddler crabs. They live in tiny burrows, each to his own, and scurry about stuffing themselves with nutrient-rich marsh mud. While the female fiddler has two claws of equal size, the male has one small claw and one big one that is almost as large as the rest of his body. He can feed only with his small claw. If you want to observe the fiddler crabs, you must find a lot of burrows and stand or squat stone still until they think it is safe to emerge. Rails and racoons feed on fiddler crabs. One way to observe this is to examine droppings for undigested hard parts. You may be observant enough to find some droppings to study. A relatively direct food chain is involved. The cordgrass traps radiant energy from the sun and converts it into organic energy. Bacteria decompose the cordgrass; protozoa feed on bacteria, fiddlers feed on protozoa, and rails feed on fiddlers. When a hunter eats a rail, the energy he gets is derived from cordgrass and ultimately, the sun.

A far more important human food source is produced by a similar food chain. If you make your way to one of the numerous small meandering marsh rivulets, you will find it teeming with living things. At this point, a long-handled dip net is useful to help you capture the tiny aquatic creatures. There are dozens of species of infant “seafood” forms in these shallow, protected, nutrient-rich streams. The “fry” of shrimp, crabs, and fish, through usually hatched at sea, make their way to marsh streams to feed and grow large enough to survive at sea. You have never eaten a shrimp that did not spend its early life in a marsh stream. At the edge of the marsh stream, you can find oyster and clam beds. These animals are filter feeders. That is, they pump great quantities of marsh water through themselves, filtering out and devouring bacteria and protozoa that got their energy from the marsh.

Another kind of intriguing marsh inhabitant is the periwinkle snail. Sometimes called the yo yo snail, it works its way up and down cordgrass stalks feeding on bacteria or protozoa.

Watch out for the horse clam. It lives with its lower half buried in marsh mud, and the protruding shell is razor sharp. If you do cut your foot in the marsh, chances are, it will be done by stepping on a horse clam.

Marsh Viewing and Touring Locations Georgia’s salt marshes are accessible from literally hundreds of places along the coast. Many of the access roads are privately owned; but the marsh itself is, in most instances, state property. The following routes, shown on the accompanying map, provide access to the marshes.

  • From Midway, take GA 38E to Colonel’s Island, about 13 miles.
  • From South Newport, take GA 131E to the vicinity of Harris Neck National Wildlife Refuge, about 7 miles.
  • From Eulonia, take GA 99 east and south toward Darien, about 18 miles; the road passes near marshes in many places.
  • From Spring Bluff, take GA 119 to Dover Bluff, about 8 miles.
  • From Kingsland, take GA 40 spur to Crooked River State Park.

It is best to visit marshes at low tide when more is exposed.

This tour was written for Brown’s Guides by the late Philip Greear, a native of Troutdale, Virginia and a long-time resident of Helen, Georgia. Philip was chairman of the department of biology and earth science at Shorter College in Rome, Georgia; and a national visionary in teaching and advocating the preservation of the natural ecosystem. He used the Georgia Barrier Islands as an outdoor classroom for teaching marine biology and environmental science.

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