No. 04–Marsh Grass

Next to the water, marsh grass (Spartina alterniflora) is the single most important component of the estuarine salt marsh environment. It, along with planktonic plants and animals are at the very center of the food web.

The grass dies back in the fall, is broken off by wave action and enters a process of decomposition fueled by bacteria and other small organisms. The end product of this decay is called detritus. Detritus is a slurry mixture of pureed plant fiber and bacteria. Tidal currents provide year round distribution throughout the estuarine system and to near shore waters. Many species feed almost exclusively on detritus and are called detritivores.

Detritivores are generally rather small creatures, mullet being an exception, which are consumed in great numbers by larger predators. Finger mullet are on the menu of most game fish and larger mullet are an important part of the diet of osprey, dolphin and sharks.

Some species may be classified as detritivores for only part of their lifecycle. Penaeid (white and brown) shrimp and blue crabs are examples. Shrimp and blue crabs spawn offshore because the offspring require full ocean salinity (35 ppt) through their larval stages. As larva they are planktonivores consuming each other and any other organism they can get in their mouths at an alarming rate.

As post larva, the crabs which are about 2mm across and shrimp at about 5mm long begin the migration to inland waters. The detritus that has accumulated in the salt marsh through the winter months is baby food for the newly arriving white shrimp and blue crabs in the spring.

So, no marsh grass, no detritus. No detritus, no shrimp, no crabs for the pot.

As they grow, crabs become ruthless predators and scavengers while shrimp are omnivorous; feeding on algae, scavenging and hunting small invertebrates in the sand and mud.

More than shrimp and blue crabs are dependant on detritus as young. It, along with plankton, is the first food upon hatching for estuarine fish and the larval offspring of near shore fish species that use the estuary as a nursery.

The nutrient rich salt marsh does not horde its bounty. Carried by tidal, near shore and ocean currents, detritus and other estuarine nutrients both directly and indirectly feed many inhabitants of Atlantic coastal waters.

I suppose it may also be said that aside from the obvious delights of the dinner table, the calming aspect of salt marsh environs feeds a deeper need in many humans. They are nourishment for the soul and psyche in often troubled times and stoke the creative fires of artists and poets who regale us with imagery to grace our homes and hearts.

Who has not at one time or other shuttered ones mind to the distractions of the day and, propped against a tree, simply gazed out over the marsh and let care drain with the tide.

The ubiquitous stands of spartina are more than a source of material and psychological nourishment, they are also habitat providing homes, temporary cover and hunting opportunities for many species.

The often heard but seldom seen clapper rail, aka mud hen, is a fulltime resident. The little white shelled periwinkle snail lives on the grass stalks feeding on algae.

When the tide is up, many small creatures seek cover from predators in the tangle of roots, stems and leaves. The periwinkles, which don’t like to be submerged climb the stalks ahead of the tide only to be picked off and crunched by cruising diamond back terrapins.

As the tide recedes, red drum and sea trout patrol the marsh perimeter in anticipation of dining on those forced by falling water levels to give up temporary safe harbor. As the water leaves the spartina, the game fish move to the mouths of creeks leaving the mud hens to their own squawking good feed.