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Oyster Grass, Delta Journal, Times Picayune, 12-30-07 C-9

Delta Journal
by Bob Thomas

Among the harshest habitats for plants is the edge of the sea. The concentration of salts in seawater is so much higher than in plant tissue fluids that life-giving water is literally drained from the plant (via osmosis), leaving it to shrivel and die. Because of this difficult environment, few plant species have adapted to living in sea water. One of the best success stories is that of Oyster grass (Spartina alterniflora), also called smooth cordgrass.

Along Louisiana’s coast, especially in saline marshes, wide bands of this species are common, but stands of oyster grass can be found throughout brackish and some intermediate marsh. Why is this species so successful where most plants fail? Several intriguing adaptations have allowed oyster grass to invade this less competitive environment. The plants can concentrate salts in their cells, thereby maintaining a balance with the salt water and retaining sufficient water to sustain life.

Oyster grass can excrete excess salt, otherwise they would attract water from the surrounding environment and actually rupture their cells. This excreted salt is often visible and can be tasted on the surface of the stems. Since the soils of salt marshes are very organic and the microbes that live there produce copious amounts of methane, hydrogen sulfide, and iron compounds, there is little oxygen available to the roots of plants growing there. Oyster grass has overcome this obstacle by having air tubes that take oxygen from the leaves to the roots, thus allowing stable growth.

Oyster grass is an important constituent of our coastal ecosystem. Its dense roots inhibit erosion of the soil. The roots serve as “nutrient pumps,” pulling phosphorous and other elements out of the anaerobic (oxygen deficient) mud. Oyster grass marshes provide habitat for many species, including juvenile stages of many economically important species such as blue crab, menhaden, and shrimp. Possibly its most important contribution is the detritus from the dying plants and their parts that wash into the sea with each tide and serve as the nutrient source for phytoplankton, the bottom of the food chain that supports all life in the Gulf of Mexico.

Because of the rigorous habitat created by the tidal nature of our salty sea, it is obvious that few plants have invaded its interface with land. The result is vast stands of single or few species that in the past have been viewed as unproductive wastelands. The next time you visit an oyster grass dominated salt marsh, don’t simply notice the lack of diversity of plant life - concentrate instead on the marsh’s contribution to the ecosystem!

Also published in Delta Journal, The Times Picayune, March 29, 1989.