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Folgers marsh is a 17-acre salt marsh that is in very good shape.
Salt marshes have a freshwater input and that is exactly where we are.
There is a Cattail marsh across the street and where I am standing is where
fresh water
- which is water that is not salty - comes into the marsh.
The salinity here is about
8.8 parts per thousand (PPT). The temperatures is 19.6
and we have more conductivity because we are using the conductivity
meter to tell us
what the salinity is. [Most] salt marshes have what is called
a salt wedge
- which is salt water the creeps up along the bottom and fresh water that floats
along on the top. Fresh water comes from rivers and streams,
floats along the top of the saltier wedge that is coming in from the ocean.
On each tidal cycle, that ocean will push closer into the salt marsh.
On the ebb tide - when the tide is going out -
the freshwater wedge will move out. So when you are looking here in the water
column,
you are going to actually see that it is going to get fresher towards the surface.
In this case it is also not as basic
as it was at the front of the marsh. We have about 6.5 pH,
where we had closer to 7.3 pH at the very front of the marsh near
where the ocean is.
Our salinity here
- at the very surface - is right at 0.
If I lower it through the water column we are going to have a salinity of about
8.9. Now I am going to switch to my dissolved oxygen meter and we can look
and see what the dissolved oxygen concentration is.
You might [also] see that toward this part of the salt marsh we have more Cattails
- and we will talk more about that in a moment.
Right here
I have 5.3 to 4.4 PPT. So this is very fresh water.
Creatures that live here are going to be very different than they are going to be at the
ocean-side of the salt marsh. Salt marshes - in this case - are like an estuary where
they have fresh water at
one end and salt water at the other end. So let's see what our dissolved
oxygen meter says. This is measuring the amount of oxygen that is in the water.
This end of the salt marshes is going to be [much] more oxygenated
than the ocean end. We do not have as many anaerobic
creatures, we have more aerobic creatures - creatures that need oxygen
to live. So this is a lot
more fresh water that is coming in from rivers and streams.
It is going to be mixed up is going to have oxygen entrained into it.
In this case I have nice cold water,
and since I am holding it close to the bottom it is actually pretty low on oxygen
- about 21.0%
oxygen at about 1.6 mg per liter.
A lot of that has to do with the primary productivity
and all of the decaying matter that you see me standing [on]. All of this excess
material
is from the several storms [that] we have had this winter, which has spread all this eelgrass
and Cattails and decaying matter here.
That is all decaying and is taking up oxygen as it decays.
Hopefully you will understand that salt marshes are a combination a fresh water
coming into salt water where everyday
a battle is fought between the harbor, the sea
and the freshwater streams.