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Flotant Marsh, Delta Journal Times Picayune, 3-30-08, C-7

Delta Journal

by Bob Thomas

Louisiana has a special form of marsh that can be found in either freshwater or intermediate marsh. It is called flotant (flow tawnt’) by the locals (and often referred to as la prairie tremblante, or, trembling prairie), because it is a floating marsh that is not anchored to the soil beneath. It consists of tightly entangled plants and their roots, mixed with peat. Typically there is water flowing below the flotant, then some oozing soil, then clay. Patches of it may occur within normal marsh, and from the surface, it looks like any other marsh. It may be rather thin and not able to support the weight of a person, or it may be very thickly vegetated and solid enough for a human to actually walk about. If you step onto flotant marsh, you will feel like you are standing on a water bed. As you step around, waves of grass spread around you. It is tempting to jump up and down, but the flotant is rarely thick enough and you usually end up falling through.

Though there are similarities, the overall ecology of flotant is very different from that of freshwater and intermediate marsh. By definition, flotant is floating, so it is never inundated with water and covered with sediments as the others are on occasion. However, some floating marshes don’t float all the time, lying on the bottom for part of the year - and maybe even being covered sometime by water if they become partially rooted.

If there is too much rooting, there is danger that the flotant will be so rooted that, when the water rises again, the “floating marsh” stays attached and is drowned and may die.

Over time, as the floating marsh thickens, new and larger plants are able to grow on the mat. In some places, there comes a time when woody plants, especially Wax Myrtle (Myrica cerifera), can grow and be supported by the floating marsh. Even small cypress trees and the like can grow under some conditions. When this happens, the floating marsh is changing and may someday become swamp forest as the cypress and tupelo take over. This is a remarkable change since the area goes from being open marsh (water with no woody plants) to swamp (water with woody plants).

In order to have a truly balanced ecosystem in America’s WETLAND, we need to protect all its components - and flotant is a very important segment.