SANDY BEACHES

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SANDY BEACHES
Rocky and sandy shores share many of the same
characteristics
- wave shock
- changing temperatures
- changing salinity
- desiccation
- predation
- good food supply
Life on the floor at the shore is the most
difficult marine environment due to lack of
stability.
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Sand is constantly in motion and so zonation is
less distinct than on rocky shores. Beach
zonation is determined by daily tides.
1. Supratidal - upper beach area where materials
are stranded by high tide (strand line).
Because sand contains little food, scavengers
must search along the strand line for beach wrack
(decaying organisms).
Inhabitants adapt by burrowing to reduce abrasion
and escape the heat and predators.
ex clams, fleas, ghost crabs, insects, reptiles,
and rats
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No two beaches have the exact same sand. From the
red sand of Prince Edward Island to the sugary,
white sand of Siesta Key, Florida to the
jewel-like pebbles on some Hawaiian beaches,
sands have an amazing variety of color and
texture.
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2. Intertidal - area from high to low tide
least stable area with the highest diversity of
life.
The sand is wet by the capillary action of
evaporating water.
ex cord grass, bacteria, phytoplankton, worms
3. Subtidal - always just under water most
stable surface
ex eel grass, crab, shrimp, sand dollars,
flounders, mollusks
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In the winter, high energy waves erode the
beaches pulling sand back into the sea.
Summer waves are weaker and deposit sand on the
beach (foreshore) where dunes can form.
Dunes occur throughout the world but are largest
on coasts with a wide continental shelf to supply
the sand to build dunes.
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Succession of dune communities follows this
pattern
1. Pioneer Winds blow sand off the beach where
it is trapped by sea grasses.
Their roots stabilize the sand and dunes begin to
form.
NOAA
Sea grasses are protected by law.
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The windward dune face usually has a gradual
slope, while the leeward side is steep - (called
a berm). It prevents land breezes from blowing
sand back into the ocean.
2. Juvenile Behind the dune, is the swale - a
low area where breezes are deflected and the
result is furnace-like temperatures.
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3. Mature Secondary dunes form behind the swale.
They are vegetated with woody shrubs and
eventually a maritime forest develops.
Beaches are protected by the dune. Dunes are held
in place by grasses. Grasses come from seeds
deposited by birds feeding and nesting on the
shores.
Birds build beaches and dunes!