I'm away from my work computer for the day, but off my head hydrogen
sulfide is generated by certain bacteria in anoxic, reducing conditions in
wetland soils. it is toxic to plants as well, although wetland plants,
especially saline marsh plants, can tolerate it. I have much more
knowledge of plants than of soils and biochemistry, but here it goes.
Anyone on the list (Adam?) should feel free to correct me, most of my
knowledge comes from reading papers by Dr. Mendelssohn at LSU, and talking
to Dr Jenneke Visser at ULL about plants. There's one in particular that
i can forward later.
basically, if you have collapsing marshes, that are "waterlogged," the
soils are likely anoxic and reducing. if you step or stir the soil, and
gas bubbles up, and it smells like rotten eggs, the collapsed/ing marsh is
producing some amount of H2S. The amounts generated are very low compared
to industrial sources.
many marsh plants have an alternate metabolism for their roots, which are
often underwater, in low or no oxygen conditions. H2S screws with this
anaerobic metabolism. Often, sulfide is associated with saltwater, as
certain ocean salts carry the sulfur. saltmarsh plants are apparently more
capable of dealing with H2S. So my expectation is that salt marshes will
produce more H2S under the collapsing condition.
The site i picked i is not as salty as i would have liked, but I picked it
because it was one of the closest collapsed marsh sites to a highway. It
was bare of plants post Katrina, and has received saltwater from Katrina
and from a flawed management decision--to flood the polder it sits within
with 12 ppt saltwater from Lake Pontchartrain.
Shannon was inspired by our trip out to Big Branch, where I demonstrated
the need for marsh restoration in the area by stepping in the existing
waterlogged marsh, which bubbled furiously at each step, and stank of
rotten eggs ( i think i have some video of this on flickr). Bayou Sauvage
is not as "bubbly" as that site, but it's very accessible and bubbles. I
think you can see the white foam in some of our photos of Bayou Sauvage.
The marsh in Bayou Sauvage has already totally collapsed at least once--I
have this knowledge from trying to re-plant it post-Katrina. the area is
behind a levee and under pump--this hydrologic alteration has degraded the
soil conditions. The area is managed for ducks, not plants--and so the
polder is artificially flooded at times, because the migrating ducks like a
lot of standing water.
USFWS and NOSCB had planted bullrushes and *Spartina *grasses there (see my
2009 photos)-but they didn't take. *Typha* has naturally colonized the
area. *Typha *is a plant that is more agnostic of salted and anoxic and
sulfuric soil conditions and high water variability. Its presence, as well
as the site's history, indicated to me that this was a good site to try.
The site was under a drainage regime during our trial--the pumps were on.
the soil at bayou sauvage bubbles and smells a bit rotten eggy--but not as
much as Big Branch. it's a 60 min car ride and 45 min canoe into the site
at Big Branch, which takes at lot more planning.
if the strips aren't sensitive enough to pick up on the H2S that was
there--and i'll have to get to my work computer to give you the expected
numbers, I would try it again at a more brackish and bubbly site. i will
keep an eye out and ask around.
perhaps across the bayou from the wetland watchers site out of NORCO. Or
perhaps fountainbleu park a mile off the boardwalk, or off Hwy 11 on the
northshore. the trouble with the more brackish, waterlogged sites in LA
that i am familiar with is that most of the good and screwed up ones
require a boat (at least a pirogue) to access. The Woodlands Conservancy
soils definitely stank of rotten eggs, perhaps we can try there, even
though it's freshwater. That is a former swamp that has been severely
drained, and the soils have collapsed. The older trees are five feet in
Sara, Shannon, i will make a list of other possible sites to visit and
assess if we want to repeat this trial in a bubblier, stinkier site.
On Wed, Jul 4, 2012 at 2:54 AM, Shannon Dosemagen <
504 237 0323
504 484 9599
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