Transcript Salt Marshes - Abingdon School Study Site

Salt Marshes
• Salt marshes are coastal wetlands rich in
marine life. They are sometimes called tidal
marshes, because they occur in the zone
between low and high tides. Salt marsh
plants cannot grow where waves are strong,
but they thrive along low-energy coasts.
Where are Marshes Located?
What are Their Features?
• Salt marshes are transitional areas between land
and water, occurring along the intertidal shore of
estuaries and sounds where salinity (salt content)
ranges from near ocean strength to near fresh in
upriver marshes.
• Because many salt marshes are influenced by the
twice daily rise and fall of tides, they are subject
to rapid changes in salinity, temperature and water
depth.
• Salinity, frequency and extent of flooding of the
marsh determine the types of plants and animals
found there.
• The low marsh zone floods twice daily in most
UK environments, while the high marsh floods
only during storms and unusually high tides.
Animals and plants live in these zones of the
marsh, depending on how well they can withstand
the drier conditions of the upper marsh or the wet
conditions that regularly occur in the lower marsh.
The Vegetation
• Salt marsh plants are adapted to a harsh,
semi-aquatic environment and saline soils.
Species diversity is low. Stout stems, small
leaves, and physiological adaptations for
salt excretion and gas exchange characterize
the inhabitants of the salt marsh, which are
mostly grasses and low perennial herbs.
• The tangle of marsh plant roots and stems helps to
stabilize the muddy bottom, as well as to trap
debris and dissolved nutrients with each tidal
cycle. Bacteria convert this oasis of detritus into
food resources for microscopic algae, invertebrate
larvae, and larger animals. Salt marshes are about
twice as photo-synthetically productive as corn
fields and provide critical nursery grounds for
numerous organisms.
Algae and sea lettuce
a
b
c
Species composition and
zonation
• Species composition and zonation in the salt
marsh are governed by salinity gradients in
combination with the amount of intertidal
exposure.
• Eelgrass, Zostera marina, for example,
occupies the lowest or most marine zone. It
cannot tolerate a freshwater environment or
intertidal conditions that would expose its
roots to air.
• Cordgrass, Spartina foliosa, occurs in the
marine-to-terrestrial transition zone,
characterized by lower salinity and periodic
exposure to the air. Shoreward, where
conditions are even drier, species belonging
to the genus Salicornia are common.
Cord Grass
• On higher ground, where tidal intrusions are
rare, the wiry, prickly-leaved succulent
jaumea, Jaumea carnosa, is common, as are
the bushy shoregrass, Monanthochloe
littoralis; tall and slender sea arrowgrass,
Triglochin maritima; and endangered salt
marsh bird's beak, Cordylanthus maritimus.
Jaumea carnosa
Monanthochloe littoralis
Cordylanthus maritimus
Triglochin maritima
• The green, wiry-leaved saltgrass, Distichlis
spicata, is widespread, occurring from the
middle to high marsh, as well as in dunes
and on salt flats. An unusual salt marsh
plant is the orange, parasitic dodder,
Cuscuta salina. Its tiny, scale-like leaves
and thread-like stems frequently invade and
cover large areas of vegetation.
Salt Grass