Transcript Southern New England Habitats II: Tidal Marsh

Southern New England Habitats II: Tidal
Marsh
• Definititon: Tidal marshes develop in the quiet water, low
energy environments behind barrier beaches at places where
freshwater streams enter the ocean. Such mixing zones
between fresh and salt water are estuaries. They are subject
to daily tidal inundation.
• Physical environment: Tidal marshes also are an extreme
environment, in that organisms living in them must tolerate
tidal fluctuation and water salinity.
• Diversity: As with beaches, richness of terrestrial species may
be low, because few species possess the adaptations necessary
to survive this environment. The density of these species may
be high, however. Even marine species must contend with
environments that are periodically flooded and that show wide
swings in water salinity.
Topography: the Low Salt Marsh
• The area above the mid-tide level is the first to be extensively
vegetated by terrestrial plants. Near the mouth of estuaries,
this tidal water is highly saline, and tidal salt marshes develop.
• The predominant species in this zone is a tall, coarse grass- salt
marsh cord grass (foreground).
• Below the mid-tide level, mudflats are exposed at low tide.
• In New England, most low marsh occurs at the seaward edge of
tidal marshes and along tidal creeks, such as the one in the
photo.
High Salt Marsh
• Above the high tide level is a region flooded only several times
a month by “spring” tides (tides associated with the full and
new moon).
• This high marsh is vegetated by a finer, tussock-forming
grass- salt meadow cord grass.
• Much of the surface of New England salt marshes is covered
by high marsh.
Salt Pannes
• Low spots on the surface of the high marsh may fill with tide
water, which is then trapped in them.
• As the water evaporates, it becomes hypersaline, creating
conditions which few plant species tolerate.
• A stunted form of salt marsh cord grass grows in these areas,
as does the fleshy-stemmed saltwort and various types of
algae.
• Numerous invertebrates may be found in pannes, and these
are a valuable food source for species like migratory
shorebirds.
Upper Marsh
• In areas with greater microelevations (elevations inches
above those of lower parts), tidal flooding becomes even less
frequent.
• In these regions, plant species like spike grass and black
grass (actually in the rush family; visible in the center of
this slide) predominate.
Upland Border
• The upland border of tidal marshes are still less frequently
affected by tidal flooding- usually only during wind-driven
storm tides.
• They are characterized by salt-tolerant herbaceous species
like switchgrass (foreground) and woody shrubs like high
tide bush and groundsel tree (white flowered shrub).
Profile of a Southern New
England Salt Marsh
Adaptations
• To inhabit the salt marsh, plants and
animals have developed mechanisms to cope
with environmental conditions.
• The sharp-tailed sparrow (above) has
kidneys that remove excess salt from its
tissues.
• The saltwort (left) has fleshy stems that
helps to dilute salts in its tissues.
Brackish and
Freshwater Tidal
Marshes
• Water salinity steadily
drops upstream along
estuaries, although tidal
action may extend inland
many miles.
• When water is slightly salty,
brackish tidal marshes
dominated by reeds and
cattails develop (below
right).
• Further upstream,
freshwater tidal marshes
dominated by bulrushes,
pickerelweed and water
horsetail develop (above
right).