Delta Journal
by Bob Thomas

America’s WETLAND, the most vast coastal wetland in the U.S., has a unique type of marsh.

We know about salt, brackish, and freshwater marsh, but Louisiana’s coastal marhes are so expansive that there is a fourth type called intermediate marsh. This has actually been known for decades. The early wetland ecologists W. T. Penfound and Edward Hathaway called it “near fresh.”

As the name implies, intermediate marsh shares qualites of freshwater and more saline marshes. In fact, it is always found between freshwater and brackish marshes.

It is characterized not by unique species. Instead it is identified by its unique assortment of species. Since the sality of the water ranges between that of salt and fresh marshes, intermediate marshes are identified by the presence of wire grass (Spartina patens), the dominate plant of brackish marsh, and an infusion of typically freshwater plants such as cattail (Typha), water lily (Nymphea), and three-corner grass (Schoenoplectus).

It is so visually obvious that intermediate marsh can be discerned in a fly-over several hundred feet above the marsh.

There are no animals that specialize exclusively on intermediate marsh, but alligator nesting densities are highest in this habitat. Intermeidate marsh is also second in numbers of otter in the Barataria region. Nutria and muskrat do quite well there, and appear to especially love the three-corner grass.

Intermediate marsh may be very productive, but it is threatened by the encroachment of salt water. As the saline water increases, species diversity of the plants decrease, and animals depending on that diversity are diminished as well.