I don’t think anyone’s ever written a riveting story about grass, but if you were, you’d have to make sure the type of grass is worth talking about. The spartina grass we have that’s found in our salt marsh definitely fits this bill.
Formally called sporobolus alterniflora, and known as smooth cordgrass, it’s the basis of our marine food web. While few organisms actually eat the grass while its alive, plenty of creatures need it for their continued growth and survival.
SURVIVAL OF THE FITTEST
How tough does spartina grass have it? Well, consider the obstacles it goes through for survival.
First, spartina is a freshwater plant that lives in saltwater. When faced with an submergence of saltwater, most freshwater plants would perish, but spartina has a trick up its sleeve. Through a process of desalination, the grass draws in saltwater through its roots, “sweats” out the salt, and retains the fresh water. If you were to look closely at a spartina stalk, you’d see salt crystals along its stem and leaves.
Because the marsh is inundated with saltwater from tidal flooding, the soil itself has very little oxygen in it. In the soil exists bacteria that actually creates its own oxygen to survive, and in the process emits a byproduct, hydrogen sulfide, that permeates the soil. At low tide you can actually smell this rotten egg scent.
But this hydrogen sulfide presents another challenge to spartina’s survival. High concentrations of hydrogen sulfide are highly toxic to all plants. Spartina is no different here, so why does it flourish here? Well, the plant has an ingenious solution.
Spartina has hollow air tubes that run from the top of the stalk down into its roots. The tubes draw oxygen from the air, down its stem and to the roots, which release the oxygen directly into the soil. This oxidizes the hydrogen sulfide in the soil immediately surrounding the root system, converting it to iron sulfate, which is a non-toxic sulfur. As the roots grow, this little bubble of iron sulfate enriched soil expands, protecting the plant!
SPARTINA: PROTECTOR OF THE LOW COUNTRY
So why is spartina so important? As mentioned before in a previous post, we have really, really high tides. When we have an incoming tide, the grass is almost fully submerged. This allows juvenile fin fish, shrimp larvae and small crabs to use the salt marsh as a nursery. Hiding in the spartina gives these young organisms a chance for survival from predation. It is estimated that over 70% of all commercial seafood caught off of the coast of the United States will have spent some portion of their lives in these nurseries.
Another reason for their importance is as an erosion barrier. The spartina lines the tidal creeks of the salt marsh and runs all the way to the tree line. The seasonal storms we have can bring significant waves and tidal surges. This grass is a first line of defense to absorb wave action and diffuse it before it reaches the land.
A FOOD SOURCE FOR MANY
Like all things living, spartina eventually dies, but even in death, the grass brings an abundance of life.
The dead spartina grass, called wrack, eventually makes its way out of the marsh on a high outgoing tide. It gets washed out of the creek, out into the sound, and eventually out into the Atlantic Ocean. While this is going on, the grass is decaying into detritus. Small microorganisms called phytoplankton will feast on the detritus. The abundance of feeding phytoplankton bring in zooplankton and small fish to feast on them, and in turn, larger organisms like fin fish, crabs, rays and dolphins eat the smaller creatures.
GRASS AS A BEACH BUILDER
And just when you think the grass couldn’t do any more, it has one last role to play. As it floats around the Atlantic, much of the wrack eventually finds itself along our beaches. Here it performs its second duty of an erosion barrier as the wrack breaks down into smaller fragments. It blends in with our fine sand, reinforcing the beaches, creating sand dunes and berms. The dunes then become annual nesting sites of sea turtles! Loggerheads, greens and leatherbacks all make appearances every year laying thousands of eggs right here on Hilton Head.
From the salt marsh, to the waterways, to our beaches. Spartina plays an irreplaceable role in the ecology of our island. Without it, we wouldn’t have the diversity or the beauty we often take for granted. Such a simple stalk of grass that does so much to bring life and protect it. As far as grasses go, spartina is indeed pretty cool. While on your next dolphin tour, you can appreciate all that the spartina does for us.