The magical salt marsh ecosystem is a living, breathing entity nurturing salt marsh animals, commercial fish species and salt marsh plants. And it's critical to the health and welfare of humans.
Welcome stalwart members of the Adventurer's Corp, kids of all ages and ethnicity, brought together by a love of adventure, exploration and learning. Today we're going to explore the Marshes of Glynn, the very salt marsh ecosystem made famous by the poet Sydney Lanier in his poem entitled, appropriately, "The Marshes of Glynn."
You're standing on the dock at the Jekyll Harbor Marina and the contraption in the water before you is the Argos, a very special submersible. This purple-painted submarine (with the yellow smiley face stenciled on the side) has a unique trait - it can shrink down to the size of a fish.
Line up, take your time, and climb aboard. Watch your step, now.
Everybody settled in? Good. We're off to get a fish-eye perspective on the Marshes of Glynn.
Marsh Ecology -
Okay. We've left the marina and already we've shrank to the size of a shad. Didn't feel a thing, did you?
First we'll have to cross the Jekyll River. The tide is rising, and the current will help carry us into the marsh, where salt marsh animals and salt marsh plants abound.
Tides play an important role in the ecology of a salt marsh ecosystem. As the tide rises and falls twice a day, tidal surges deliver nutrients and distribute them throughout the marsh. It also returns nutrients from the marsh back to the estuaries and bays.
Salt marsh plants won't grow where there is energetic wave action, like on the unprotected Atlantic side of Jekyll Island. They develop on low-energy coasts, places like estuaries and the bay or river side of barrier islands. The tides are gentle here, and this enables marsh vegetation to get a foothold.
Because of its relation with the tides, the salt marsh ecosystem is sometimes called a tidal marsh.
Look out the portholes. You'll see that the water is awash in detritus, moving with the tide. What's detritus? It's the remains of decayed, nutrient-rich organic matter from plants and animals. All this decomposing detritus serves as a banquet for many organisms, including mammals. Micro-organisms eat decaying grasses, and these are eaten in turn by fish and birds.
Types of Salt Marsh Animals -
What kind of animals live here? Well, lots of crustacean and fish species use the protection of the marsh grass as a nursery for their young, and many different types of birds either nest or feed here. Mammals like marsh hares and raccoons forage through the marsh, and also use the long grasses as cover.
The Argos Arrives at the Marsh Edge -
The Argos is slowing now, ready to move up one of the side creeks draining into the Jekyll River. Small fish dart around us, and just ahead, close to the bank, a blue crab scuttles in his funny sideways walk across the creek bottom.
We'll have to stay well away from him - he might mistake us for food, and his pincers could crush our shrunken vessel, like a red neck crushing a beer can.
The height of the tide determines the flooding depth and, consequently, the height of salt marsh plants that can live in the two marsh zones - low marsh, which is usually flooded twice a day, or high marsh, which is only flooded during storms or unusually high tides.
The amount of salt also has a bearing on what plants and animals can live where. Closer to the sea, the water is more salty. Inland, river outlets bring in more fresh water to dilute the salt content.
Salt Marsh Grass -
If you arrived at Jekyll Island by car you crossed the causeway, and probably noticed the salt marsh spreading all around you. Grass everywhere! It might look plain and barren, but what's surprising is that there are several species of grass in a salt marsh, and an abundance of other biological forms, much of which lives out it's life unseen by humans.
Look outside. The Argos is nosing into a forest of smooth cord grass, which grows in the lowest areas, those that are frequently flooded. Smooth cord grass is tough, and actually secretes excess salt through special glands.
As we move further into the salt marsh maze, into zones only periodically flooded, we'll discover saltmeadow cord grass.
The biological classification of the cord grasses is halophytic, and salt marsh animals won't eat them. When the grass dies, however, it decomposes and is eaten by various micro-organisms. These organisms then serve as food for fish and birds.
Where low marsh gives way to high marsh, black needle rush grows. And the plant growing along the edge of the salt marsh is sawgrass (actually a freshwater plant). All of these plants are salt-tolerant to one extent or another.
Oh oh - there are lots of little fish fry zipping around the Argos. Something seems to have spooked them, and they've swam deeper into the cord grass, seeking shelter. If we turn on the sub's bow lights, shine them into the creek, maybe we can see...
Yikes! A dolphin just cruised past, swimming up the creek, heading deeper into the marsh on the rising tide. Dolphins sometimes swim up a stream, actually herding fish ahead of them, and will even chase fish up on a sloping mud flat. The dolphins then literally drive themselves out of the water and up on the mud flat with their powerful flukes, where they grab the fish before sliding effortlessly backward and into the water.
Glad the Argos wasn't in the creek when the dolphin swam by - we could have been dolphin bait!
The tangled mass of salt marsh plants is the perfect spot to hide from predators. Many important marine fisheries species seek shelter in the cover of the grass when young. And the nutrients flowing from the marsh lands at low tide nurture an abundance of commercial marine species.
In fact, if it wasn't for the marsh and it's nurturing abilities, you wouldn't have had that shrimp for dinner last night.
It's a Bird's Life -
We've piloted the Argos further into the cord grass, into the leading edge of black needle rush. Towering above us, a blue heron balances on stilt-like legs, prowling the shallows for small fish and fiddler crabs.
Look through the periscope - maybe you can spot other birds that nest or feed in the marsh, like cranes, egrets, and gulls. To the birds, the salt marsh ecosystem is a rich oasis, teaming with a seafood banquet - fiddler crabs, periwinkle snails, and small fish. They also feed on the abundance of insects living in the salt water ecosystem.
Transitional Zones -
The entire salt marsh ecosystem is a transitional zone between the sea and the land. Within this ecosystem, however, are other zones of transition. These "edge" environments support an abundance of plant and animal life.
The low marsh supports mostly smooth cordgrass (there are two forms - one grows up to 9' tall along creek banks; the other lives within the interior of the low marsh zone and grows from 2' to 3').
Several species co-exist within the high marsh. This is the home of black needle rush, which lives side by side with salt meadow cordgrass and the short form smooth cordgrass.
High marsh edges into another transitional zone - the marsh-upland border. This is where the salt marsh ecosystem grades into a maritime shrub mixture of wax myrtle, yaupon holly and cedar.
Salt Marsh Ecosystems Protect Human Habitat -
Okay, kids, time to point the Argos on a heading back to Jekyll Harbor Marina.
You've learned a lot about how the salt marsh ecosystem around Jekyll Island works. The importance of this environment was not always recognized, though.
In the past, much of this environment was drained or filled in for development. It's been estimated that over half the original salt marsh ecosystem in the United States has been lost.
If you want a graphic reminder of how important the salt marsh ecosystem is to the health, safety, and welfare of human life, just remember the effect Hurricane Katrina had on New Orleans, which long ago dredged and filled it's vast marshlands in the name of progress. Now the city sits unprotected, slowly sinking below sea level, at the mercy of ocean storms.
We've learned, however. Federal and state laws protect this vital habitat, as humanity recognizes its importance to our well-being.
You've learned that salt marsh ecosystems nurture many important marine species. They also filter pollutants, like sediments and toxins, washing down from the uplands, and protect the mainland by buffering and absorbing storm surges.
And don't forget their
aesthetic value - they're beautiful environments - serving as perfect
frames for your Jekyll Island Family Adventure.
"And I would I could know what swimmeth below when the tide comes in, On the length and the breadth of the marvelous marshes of Glynn." - Sydney Lanier