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The Floating Marshes of Louisiana: A Unique Ecosystem

Information presented is factual at the time of creation.
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Dr. Swarzenski: We are only about 15 miles away



from New Orleans and the Mississippi River in a



beautiful example of a floating marsh that has been



pretty much unmanaged for many, many years---decades.



There’s fire that comes through here, and that may be



about the only disturbance. It’s a continuous, almost prairie-like



expanse of a marsh, a freshwater marsh, without any



interruptions by little waterways or ponds or lakes.



This is just a solid, solid meadow of a freshwater marsh.



Narrator: Extensive floating marshes occur in a few



locations around the world. Papyrus swamps of tropical



Africa occur along the White Nile, the Okavango and Niger



deltas, and along the shoreline of Lake Victoria. There



are extensive Phragmites swamps in the Danube Delta in Romania.



Seasonal and permanent floating meadows are found in the middle



Amazon flood plain. And in the Mississippi River



Delta Plain, there are large expanses of floating



marsh, which are the focus of this video. This



unique ecosystem is dominated by a variety of



grasses and forbs, which can create a buoyant



mat that floats on a layer of water. Different



terms are used to describe floating marshes





and reflect the country of origin. In Louisiana,



they are often referred to as flotant or prairie tremblant.



The best way to get around floating marshes is by airboat.



Dr. Swarzenski: If you stay in one place for any



length of time, eventually the water...your ankles



will start being inundated with water, but this kind



of marsh pretty much never on its own, never gets



flooded. It’s always dry, and there’s always one or



two inches of unsaturated zone near the, near the top,



and then it’s almost always saturated below that.



Narrator: Floating marsh, or flotant, forms a



buoyant mat of air-filled roots and rhizomes, which



allows the marsh to float up and down as water levels change.



Over time, the marsh mat may thicken, becoming



strong enough to support woody plants such as



wax myrtle. Periodic fires, however, keep the woody



growth in check, allowing the herbaceous plants



to continue to dominate the marsh.



[laughter]



Dr. Swarzenski: There’s some buoyancy to this marsh.



This is what we would call about a five on a scale



of one to five in terms of buoyancy. You can see the



water’s going around my ankles because I’ve been



standing here for a while. And I’m going to walk



away from here, and then everything will rebound.



Narrator: Peat buoyancy varies among marsh types.



From most to least buoyant, are maidencane, bulltongue, and wiregrass.



Dr. Swarzenski: This area gets burned regularly..uhm.. so



there’s nothing crowds out other species.



Nobody really takes over….no one species takes over,



and there’s a huge diversity of plants and grasses



and forbs and orchids. There’s four to five species of



orchid that we’ve seen out here. This is



Calopogon tuberosus right here. There’s two



different kinds of ferns….Thelypteris palustris



and Osmunda regalis. This is Thelypteris. Wax myrtle



would start invading this area, if it was not burned



every year and eventually there would be 10, 15 feet



tall wax myrtle thickets out here.



In Nova Scotia, there’s these areas of wet meadows,



wet bogs, called red orchid bogs. And they have



the Calopogon; they have the Pogonia that we see



out here, The, the Junonia, the buckeye… common



buckeye. Here’s an example of an orchid. And then just a lot of ferns.



Ah..it’s also common in Nova Scotia. So this is all



northern temperate environment with very harsh



winters. And yet here we are in Louisiana a few miles



away from New Orleans and we see a very similar kind



of a peat system. The soils here are highly organic;



there’s almost no clay or silt. Even though the



Mississippi River is close; it of course is kept from



coming in here by the flood control levees.



Narrator: Floating marshes form when an attached



marsh forms an organic mat that later detaches



from the underlying mineral soil. They may also



form through infilling as floating fragments expand



and as vegetation extends from an adjacent marsh



forming a floating mat over a body of water.



Dr. Urbatsch: They’re usually pretty early bloomers…



Dr. Swarzenski: OK so you already have.. what you..



I mean, it’s worth.. going and looking for.



Dr. Urbatsch: Well, yeah, I’d like to find one in flower.



Dr. Swarzenski: A few weeks ago in that same area



there were a lot of them, and now I just saw one.



Right here is Habenaria nivea, which is a very good name for it.



Dr. Urbatsch: It’s a winner, It’s been reported for



Louisiana, we actually don’t have a specimen of it.



Dr. McKee: OK.



Dr. Urbatsch: So it’s that rare.



[laughter]



Dr. Swarzenski: Right. We’re in the subtropics at 29



degrees and there’s these half a foot to 12 inch tall



peat mounds that may be as much as 10, 15 yards in



diameter and they just cover this whole area where



we’re at. They grow..Panicum grows through it uhm..



it survives burning. It seems to have come in recently…



since about 2000. Before that I didn’t notice…



any of these…I saw some small mounds, but



nothing of the scale that we see now.



Somebody from Quebec ended up with two samples



of Sphagnum from the national park, which is about



five miles to the east here. And he identified two separate



species of Sphagnum moss down here. And he,



working up in Canada, was kind of surprised to



see these two species in the sub-tropics.



[distant voices]





Details

Title: The Floating Marshes of Louisiana: A Unique Ecosystem

Description:

Extensive floating marshes occur in a few locations around the world. Papyrus swamps of tropical Africa occur along the White Nile, the Okavango and Niger deltas, and along the shoreline of Lake Victoria. There are extensive Phragmites swamps in the Danube Delta in Romania. Seasonal and permanent floating meadows are found in the middle Amazon flood plain. In the Mississippi River Delta Plain, there are large expanses of floating marsh, which are the focus of this video. This unique ecosystem is dominated by a variety of grasses and forbs, which can create a buoyant mat that floats on a layer of water. How these marshes form and some of their unique features are described.

Location: LA, USA

Date Taken: 5/1/2011

Length: 9:16

Video Producer: Karen L. McKee , U.S. Geological Survey


Note: This video has been released into the public domain by the U.S. Geological Survey for use in its entirety. Some videos may contain pieces of copyrighted material. If you wish to use a portion of the video for any purpose, other than for resharing/reposting the video in its entirety, please contact the Video Producer/Videographer listed with this video. Please refer to the USGS Copyright section for how to credit this video.

Source:

For more information go to: Scientific Investigations Report 2005

File Details:

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In: Water collection

Tags: MississippiRiverDelta NewOrleans WaxMyrtle bulltongue fire flotant maidencane orchid wetland

 

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