Oceans 11 – Dalesandro
Notes – Low-Tide Zone
-The low-tide zone (also known as the low littoral zone) is the next
area in the littoral zone, just below the mid-tide zone.
 The low-tide zone spends three quarters of the day (or more)
submerged under water and only one quarter of the day (or less)
exposed to air.
-The food chains and ecosystem relationships found in the low-tide
zone are more complex than those found in the high-tide or mid-tide
zone. In general, biodiversity is very high here.
 Animals and plants living in this zone are adapted to being
exposed to the air for short periods of the day.
-Conditions are still too harsh for some creatures (such as fish) to live in
this zone. Biodiversity is higher in areas submerged under water the
entire day.
-Some of the creatures found in great numbers in the low-tide zone are
sea anemones, clams, sea cucumbers, sea stars, and sponges.
 Note: some creatures from the other zones (high-tide, mid-tide)
also live in the low-tide zone.
-Beaches extend into the low-tide zone, so beach creatures such as
beach worms, rock lice, and sand flies can also be found in this area.
Generally these creatures only appear when the low-tide zone is
exposed to air.
-Since no rooted green plants can grow in the low-tide zone, food
chains in this area most often begin with algae.
 Note: Seaweed can also form the basis of low-tide zone food chains.
Oceans 11 - Dalesandro
Low-tide Zone – Organism Fact Sheet 8 – Sea Cucumber
-Sea cucumbers,
despite their name,
are animals, not
plants.
-Sea cucumbers are
excellent scavengers
and scour the bottom
of the sea in the lowtide zone for food.
-They are related to
sea stars and have
sea-star-like
mouthparts, tube
feet, and
endoskeletons.

Sea cucumbers are more properly called holothurians. There are over
1500 species known today, with up to 2000 more species as yet
undiscovered, according to some estimates.

They are scavengers and can travel in huge herds in the deepest part of
the oceans, although they are usually solitary in the littoral zone.

To defend themselves against predators, some sea cucumber species can
twist their bodies, swim upwards toward the surface, emit sticky, foultasting fibers, release a soap-like chemical into the water, or drop off
parts of their body to escape.

Sea cucumbers make up the greatest amout of animal biomass found in
the ocean. All the sea cucumbers gathered together and weighed would
be heavier than all the fish togther!

Animals that eat sea cucumbers include sea turtles, sharks, some jellyfish,
some seabirds, and humans (sushi).

Sea cucumbers have no brains. They move and react based on nerve fiber
bundles called ganglia. Each cucumber has several ganglia along its body.
Oceans 11 – Dalesandro
Notes – Subtidal Zone
-The subtidal zone lies below the low-tide zone. It is the final area in
the littoral zone.
 This zone is not exposed to air, even at low tide.
 During extreme low tides, this zone may be briefly exposed to
air.
-This area contains a very complex and biodiverse community of
organisms that live here full-time, including fish.
 Some of the most common organisms found in this layer
(besides fish) are sea urchins, periwinkles, crabs, and various
kinds of seaweed.
 Sea stars and sea cucumbers are also plentiful here.
-Wave action is still felt in this zone, as the bottom of breaking waves
rub against the sandy or rocky sea bottom.
 Because of this wave action, the organisms living in the
Subtidal zone must have ways of either anchoring themselves,
or the ability to walk or swim (to avoid being swept out to sea).
-Pollution is a major threat to the subtidal zone. It is the place where any
runoff from beaches and the backshore ends up.
 Concentration of pollutants can be much higher here when
compared to the intertidal zone or the open ocean.
 Some creatures, such as sea anemones, are very sensitive to
toxins and will disappear from the subtidal zone first, before they
die in other zones.