Written by Michele Roldán-Shaw
Photography by Ed Funk

“The Bluffton Breeze” would like to give a special shout-out to spartina grass. You may not think about this when you’re frying up a flounder, peeling back some shrimp, sucking down an oyster, cracking through a pile of blue crab, or sinking your teeth into a grouper sandwich, but spartina is the plant that made it all possible. Just because it’s not customary to order up a steaming side of cordgrass, that doesn’t mean it’s not spartina that you are ultimately eating.

elcome to May River Update #2, in which we will continue our introduction to tidal marsh ecology before we get down to the nitty-gritty with real-life tales of shrimping, crabbing, boating, fishing, oyster-picking and other human pursuits. In this article, we will examine the estuary food web, which begins with that most growin’est of grasses, the spectacularly prolific spartina.

Not all plants can stand up to the intense environment of the marsh. Salty water, fluctuating temperatures (as much as 70° in one day) and the alternate flooding and drying out caused by the tide are all conditions which would make most plants wither at the mere notion. But spartina, also known as marsh grass or cord grass, has some special adaptations which allow it to thrive in tidal zones. It can secrete excess salt in the form of little crystals, helping it to conserve moisture. It also uses extra energy to pull any available freshwater up through the ground via its roots, an expenditure which it can afford because it has virtually no competition from other plants. Each piece of grass shoots straight up to the sky, soaking up the abundant Carolina sunshine and converting it into organic matter without ever having to worry about shade from other species.

In fact, marsh grass is so efficient at photosynthesis that it is almost single-handedly responsible for making the marsh one of the most plant-productive ecosystems on the planet, rivaling even the lushness of a tropical rainforest. Scientists who study the tidal marsh’s biomass (total weight of leaves and stems found in one hectare) have found that the annual output of anywhere from 12 to 25 tons far surpasses that of even the most well-cultivated agricultural field.

So what does this mean to those of us who don’t care to scarf down a dish of seasoned, boiled spartina? Well, we are consumers; the top consumers, in fact. And spartina is the producer, providing food for the creatures that feed the creatures that provide food for us. As the old grass dies, it is washed into the water by the pull of the tide. Then it starts to break down, aided by bacteria and algae that latch onto the dead stalks. Soon they are nothing but small particles of decomposing organic matter called detritus, also known as “that floaty stuff” which you see in the water of the May River. Together with phytoplankton, microscopic algae that is the other significant producer of the estuary, a hearty meal is served up for the first level of consumers, which include shrimp, crab, worms, and filter-feeders such as clams and oysters.

Let’s take an up-close look at just one such primary consumer, the fiddler crab. The males are easily identified by their huge, overgrown claw, which contrasts quite nicely with their other diminutive claw. Right about this time of year, you’re likely to find them full-force out in the marsh, the males waving their big claw up in the air like rap stars. (They do this to attract a female. Same with fiddler crabs.) They dig a tunnel by rolling little pellets of sand and mud, then carrying them out and depositing them in a pile nearby. Once they’ve gone deep enough, they like to chill in their burrows, which they can seal up with a mud ball when the tide comes in. They feed on algae by using their tiny claw to rapidly shovel handfuls of muck up to their faces, where their mouth parts can separate out the mud and sand from the algae. An estimated 1 million fiddler crabs can co-exist on just an acre of marsh; so many that when you walk towards them, their retreat actually sounds like trickling water as 8 million tiny clicking legs scuttle across the sand.

Fiddlers comprise a single strand of the food web, one that connects a producer (algae) to a secondary consumer, such as the shorebirds, ‘coons, terrapins and fish that prey on the crabs. If a dolphin were to eat a fish that had eaten a fiddler, that would make the dolphin a tertiary consumer. Likewise, if a human were to eat a bowl of she-crab soup after she (the crab) had eaten a poor innocent shrimp, that would make the human a tertiary consumer. Of course, we also eat oysters, which are primary consumers that feed on phytoplankton, making us secondary consumers as well as tertiary consumers.

Confused yet? Well, just remember this: it all goes back to spartina. In fact, without spartina there would be no detritus because the root systems collect and stabilize sediments from run-off which, over time, become the pluff mud. South Carolina has an estimated 400,000 acres of salt marsh, more than any other Atlantic coastal state. Beaufort County has more than its fair share of that total number, which is good because scientists estimate that over 90% of commercial and recreational catch spends at least part of its life-cycle in the marsh. In other words, we have all the seafood we want right in our backyards.

Besides just being a nursery for beloved species such as blue crab, white shrimp, American oyster, bottlenose dolphin and spottail bass, the salt marsh also plays an important role in keeping our planet tidy and pure. Like any wetland, marshes have the capacity to filter water by straining out chemicals and wastes (up to a certain point, and then they just go into overload and get polluted). They also act as a natural buffer to ocean waves, and are especially helpful when they absorb flood waters after a storm. Even a huge hurricane will have little permanent impact on a healthy salt marsh; if people took care to surround themselves with spartina, pluff mud and detritus soup instead of man-made levees and artificially drained developments, they wouldn’t be hurting so bad after that Category 5 rolls through.

Thank you Bluffton for recognizing the beauty and importance of the salt marsh! We have such a thriving community of river-rats here that we could learn a lot just by listening to their observations of what they experience when they’re out on the water. Each month, the season changes and the flora and fauna of our habitat take turns stepping out into the foreground to do their fiddler dance, or their fish splash, or their leafing out, turning gold and dying back. What’s happening on the May this month?

Other ingredients of detritus soup may include, but are not limited to, clam poop, insect wings, cast-off shrimp skins, busted fiddler claws, cracked crab shells, dinoflagellate cases, egret feathers, otter fur, oyster sperm and barnacle larvae. Think about that the next time you go for a swim during a fabulous Sandbar Sunday.