ROCKY INTERTIDAL HABITAT

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ROCKY INTERTIDAL HABITAT
By Spencer Lowe
In the Intertidal Habitat, marine life is
presented with several challenges. Wave Shock
from crashing tides batter animals living on or
around the community. Every day high tides
provide moisture and nutrients to the intertidal
community, however for every high tide, there is
a corresponding low tide as well. At low tide,
the habitat dries out, causing many creatures to
search for ways to avoid desiccation. Changes in
temperature and salinity provide yet another
challenge to animals and plants living this
habitat. These changes are more drastic than
those of the sub tidal zone, providing an
difficult environment to live in. Only those
animals that are able to adapt to desiccation,
wave shock, and large changes in temperature and
salinity will survive in the intertidal habitat.
There are benefits however to those plants and
animals that can adapt to the harsh conditions of
this environment. Perhaps the most important is
the abundance of food. Intertidal communities
receive large amounts of light, which helps
promote photosynthesis. There is also a large
presence of nutrients due to the constant
replenishment of water by the crashing waves.
There are few animals that can adapt well in this
environment, but for those that can, there is
less competition for food. The rocky terrain also
provides shelter from the sub-tidal environment
which holds an almost certain death for most
intertidal animals.
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Intertidal communities are separated by a process
called Zoneation. Using zoneation we can identify
four different zones the upper, middle, lower,
and sub-tidal zones.
The upper inter tidal zone contains creatures
like periwinkles, barnacles and limpets.
The middle intertidal zone supports more species
of barnacles including gooseneck barnacles, as
well as mussels and other sea animals.
The lower intertidal zone contains sea grasses,
algae, and many of the sea animals that can be
found in the intertidal community.
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In the upper interidal zone, there are many
creatures that can adapt well to desiccation. Two
of these species are Limpets, and Gooseneck
Barnacles. Both of these creatures are able to
cling to rocks and other vertical surfaces with
great force. Limpets feed on the growths of
algae and seaweed on rocks. Gooseneck Barnacles
can be found near large muscle colonies, and
Limpet
Gooseneck Barnacles
are similar to mussels. They can attach
themselves to rocks, and clamp down their shell,
trapping water inside until the tide is high
enough to reach them. Once submerged, the
barnacle opens up its shell and feeds on
microscopic organisms in the water. Gooseneck
barnacles can live to be 20 years old, and grow
between 4 and 6 inches at full maturity.
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The middle intertidal zone contains mussel
colonies like the one seen here. Mussels are
larger than Gooseneck barnacles, but similar in
appearance. Mussels are also able to clamp down
during periods of low tide, but because they are
in a lower tidal zone, they are not exposed to
desiccation as long as their counterparts in the
upper intertidal zone. Mussels use strong hairs
called bysal threads to attach themselves to
rocks. Once there, they feed on microscopic
plants filtered out of the sea water. They can
grow anywhere from 3 inches up top 8 inches in
length! Mussels are very good to eat, and work as
a good fish bait as well.
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Perhaps the most popular creature seen in the
rocky intertidal habitat is the Sea Star.
Commonly called the star fish, these creatures
are in fact not fish at all, but rather are
classified as Echinoderms. The Ochre Star Fish
shown here was once the most abundant sea star in
California. Because they were so easy to find,
collectors and tourists would pull them off the
rocks and take them home. Not knowing how to take
they are much harder to find. They can be found
hidden in cracks or other hard to reach places
where they can not be easily seen. The Ochre
Starfish can range from bright orange to brown,
red, and even purple. Their main prey is the
California mussel, which they feed upon by
extraction with their powerful suction cups. They
also are known to eat crabs snails and barnacles
as well.
care of them however, they would eventually die.
Their numbers steadily decreased over the years,
and today
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Another curious creature found in the intertidal
habitat is the Banded Brittle Star. This star can
be found below rocks in the middle intertidal
zone, and can move very fast. They are made up of
a brown center body, and their arms are usually
gray, and contain spines and dark brown
bands.They crawl along the bottom of the ocean,
using their flexible arms to collect food like
bottom detrious. The Brittle star is one of the
most successful creatures found on earth. It can
be found in all parts of the ocean, from the deep
ocean abyssal plain, to the tide pools of the
Southern California coast.
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subdues its prey. The Green anemone also feed on
dead organisms as well. The column of the anemone
contains tubercles which it uses to collect the
shells you see here. The shells are used to
protect the anemone from desiccation during
periods of low tide. Anemones can be found in
many areas throughout the ocean, but the ones in
tide pools generally grow to only 3-5 inches.
At first glance, this appears to be a group of
dead shells, but take a closer look and you will
see this is actually a community of Green Sea
Anemones. The broken shells are animals that the
anemones capture and eat. The anemone has
tentacles that capture small crustaceans. The
tentacles secrete a poison that
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Here you can see the division of anemone at low
tide. The green tentacles are very visible below
the water line, and the anemone above the water
contain shells protecting them from desiccation.
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Perhaps one of the easiest creatures to find in
the intertidal community is the Hermit Crab.
These little crabs scamper on and around the
rocks searching for abandoned shells to make
their next home. The body of a hermit crab is
soft and flexible, making it perfect for the
spiral shape of a snail shell. When the crab out
grows its shell, it goes in search for another
shell. It will not leave its
current shell until it has found another one that
fits its body well enough. Hermit Crabs will even
fight each other over a shell. You can tell a
shell is occupied by a hermit crab because it
will move faster than that of a snail. Hermit
crabs feed during the late afternoon and evening
hours. They are scavengers, and will eat almost
anything from plants to dead animals. The only
time a hermit crab will leave its shell is to
find another shell.
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If you are exploring a Southern California tide
pool, you may encounter a California Spiny
Lobster. The Spiny Lobster seen here might look
like its missing its big claws, but its not!
The Spiny Lobster doesnt have any claws and are
mainly found off shore. Occasionally however,
Lobsters can be seen in the intertidal area, as
they become trapped during periods of low tide.
The lobster is a nocturnal animal, meaning it
hides and rests during the day, and comes out at
night to hunt for food. Spiny lobsters can reach
up to 3 feet in length and weigh over 25 pounds!
This is rare however, and most only grow to about
12 inches, and weigh about 5 pounds.Although the
spiny lobster has no claws, it can still inflict
harm by whipping its tail quickly which can cut
fingers. It is also covered by spines over most
of its body, and gloves are required to handle
them safely.
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Another animal that lives in the middle
intertidal zone is the octopus. The octopus
adapts well to the intertidal habitat with its
ability to camouflage. They can change color to
mach their surroundings, and are very hard to
find, usually hiding deep in rocks or other hard
to reach places. The octopus has a sharp bony
beak that can inflict damage on prey, and its
powerful suction cups are nearly impossible to
escape.
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A large and very important part of the rocky
intertidal community are the sea weeds which
include sea grasses and a variety of algae.
Plants provide nutrients through photosynthesis,
as well as sanctuary for small fish and other
marine organisms. These grasses prefer the soft
sediment and calm waters of the lower intertidal
zone to grow. Algae are abundant in intertidal
communities, and include red, green and brown
algae. The green grass above is the most common
grass found in Southern California intertidal
areas.
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The Rocky Intertidal Habitat is home to some of
the most beautiful and unique animals in the
world. These creatures are the cream of the crop,
being able to adapt to a harsh ever changing
environment. Surviving predators from Seagulls,
to large fish, and even humans, these creatures
have been able to evolve into the most resilient
animals on the planet.
We are truly lucky to be able to find these
animals, and experience this habitat right in our
own back yard. The tide pools of the Scripps
Institute of Oceanography, La Jolla, and Point
Loma are excellent places to see theses
creatures, and you are sure to see something new
every time you visit!