|
|
In this picture, you can see the zones of the salt marsh. The plants
change as you move from the dry land to the water.
First are the trees and shrubs growing on dry land.
Then come the
tall grasses on the edge of the marsh. Next is the high
marsh, followed by the low marsh. After the low
marsh is the open water. |
|
 |
|
Smooth cordgrass (Spartina alterniflora) is the
only marsh plant that can survive in the low marsh.
It has a hollow stem that carries air to the roots. It works
like a snorkel that lets the roots breathe underwater. It also has special
glands that
excrete salt.
You can often see grains of salt on the stems and leaves of smooth cordgrass
plants.
Photo from the National Ocean and Atmospheric
Administration (NOAA) |
|
 |
|
Black needlerush (Juncus roemerianus) is often
found in high marshes in North Carolina.
It has sharp, pointy leaves that are thick and waxy.
It acts like a desert plants. The narrow, pointy
shape
and waxy coat on the leaves helps the plant to store
water. |
|
 |
|
Glasswort or Pickleweed (Salicornia species) survives
in the salty soil by sending salt to the
tips of its fleshy stems. When salt has
built up in the tips, the tips dry up and fall off.
This removes the harmful salt from the plant.
Photo from the National Ocean and Atmospheric
Administration (NOAA) |
|
 |
|
Sea lavender (Limonium sp.) is a plant
found in North Carolina high marshes. It has light purple flowers
that brighten up the marsh in the summer.
Photo from the National Ocean and Atmospheric
Administration (NOAA) |
|
 |
|
Marsh
elder is one of the shrubs that grow on the high land in
the salt marsh. Its thick, waxy leaves prevent
water loss.
Photo from the National Ocean and Atmospheric
Administration (NOAA) |
|
 |
|
Zonation
There are three parts of a salt marsh – the
high marsh, the
low marsh, and the
creekbank marsh. The creekbank marsh and low
marsh are flooded twice a day, all year long. The high marsh is
only flooded by the tides from time to time. It may be dry for up to 10 days
at a time. Different plants and animals live in each zone.
Which organisms
live in each zone depends on how well they can stand salt,
flooding, and daily changes in temperature.
Low Marsh
Only one species of grass can stand the large changes in
water depth, temperature, and
salinity in the low
marsh. This grass is smooth cordgrass (Spartina alterniflora). It is one of the
most important producers
in the estuary
food web.
When the grass dies each fall, the stems are washed into the
estuary. Bacteria
in the estuary eat the stems and turn them
into detritus.
Detritus is the main food
source for many aquatic animals
such as fiddler crabs (see below).
The dense web of Cordgrass stems and roots holds together the
tiny grains of
clay and
silt
in the marsh soil. The grasses also absorb energy
from waves and tides that hit the shore. This protects the
land from
erosion.
Creekbank Marsh
Smooth cordgrass is also the only plant that can grow in the
creekbank marsh. The creekbank marshes grow on the small
levee
that forms next to
tidal creeks.
The levees
are higher than the rest of the marsh. The cordgrass that grows
on the levees is
not in as deep of water as the grass growing in the low marsh.
The grass on the levees can grow very tall because
it is not stressed by the deep water.
High Marsh
The high
marsh forms where daily flooding has trapped sediment and it has built up over time. The high marsh is
higher than the low marsh and is not flooded as often or as
deeply. More plants grow in the high marsh than in the
part of the marsh that is flooded every day. Some high
marsh plants are spikegrass (Distichlis spicata), Black needlerush (Juncus
roemerianus), salt meadow cordgrass (Spartina patens),
sea ox-eye and glasswort (Salicornia species).
In the high
marsh, the sun dries the soil when it is not flooded.
Evaporation
removes water from the marsh but leaves the salt behind.
This makes salt build up in the soil. Plants that live in
the high marsh have
special adaptations that
help them live in very salty soil.
Plants that can not stand salt grow above
the high marsh. This area only floods once in awhile.
Rain mixes with the salt water in the soil and makes it less
salty. Brackish
marsh plants like big cordgrass (Spartina cynosuroides)
are common here. Shrubs like marsh
elder and wax myrtle also grow on the border of the high marsh.
These same shrubs grow grow on
hummocks,
or hills in the middle of the marsh.
Click on the map at left to see your next task... |
