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Honors Marine Biology
Module 9
Intertidal Zones
January 17, 2013
Class Challenge
Birding Field Trip
The
Celery
Fields
Make up Field Trips
Intertidal Zone
The Area of Shoreline between high and low
tides. Also known at Littoral Zone.
This coastal strip where the land meets the
sea is by far the smallest area in all the
world’s marine environments, yet more is
known about it than any other.
Intertidal Zone
• This is a narrow strip of land that is only a
few meters in width, and it is defined as
the area between the oceans’ high tide
and low tides.
• Although it is small, it is the most
accessible place to scientists, and is
therefore the most studied marine habitat.
Littoral Zone or Intertidal Zone
• Even though this zone is small, it has the
greatest variation of environmental factors
as compared to any other marine
ecosystem.
• There are even several differences within
a single square meter containing huge
diversities of life.
Intertidal Communities
As the tides rise and fall, covering and then
exposing areas along the coast we can
observe the dramatic changes in the
environmental conditions.
• Most intertidal plants and animals
experience a time of stress during low tide.
• They are exposed to the air, which may be
hot or freezing.
• If it rains, these marine organisms will be
exposed to an overabundance of fresh
water.
Also, the exposure provides an opportunity
for land predators, such as birds and
rodents to move in.
At high tide, the area returns to an aquatic
environment. This brings moderate
temperatures and high salinity levels, and
it also replenishes nutrients and dissolved
gases necessary to many of the creatures
that live in the intertidal zone.
During High Tide
Waves and surf return to the intertidal zone.
Wave movement can wash away
organisms that do not have the ability to
either hang onto the rocky surface or
burrow into the sand.
The waves can also push rocks and debris
onto organisms crushing them.
• Waves can also be beneficial to organisms.
• Waves bring nutrients, carry off reproductive cells
and accumulated wastes.
• Wave energy shifts soft sediments and shapes the
shoreline.
• Waves constantly remove fine sediments from
rocky shores, resulting in a hard bottom, and wash
away; fine materials from beaches, leaving only
grains of sand. These finer materials will be
washed out to sea and deposited in more
protected bays and lagoons.
Substrate
Is the bottom surface of a marine habitat.
It is the type of material located on the
bottom and provides the basic habitat and
determines what organisms can live there.
A soft sandy substrate produces a different
type of environment than a hard, rocky
substrate.
The variety of tidal conditions, bottom types,
and wave strengths create different living
conditions for the organisms living there.
Rocky Intertidal Zones
• This is a harsh area for organisms to live.
• Rock boring sea urchins and clams,
burrow into the rocks so that they are not
swept away by the waves.
• Most organisms just hang on tightly to the
rock.
Epifauna
Animals that hold on to the surface of a
substrate, including sand or mud, are
called epifauna.
They either crawl about the sea bottom or sit
firmly attached to it.
When an epifaunal organism is attached to a
substrate, it is referred to as sessile.
Rocky Intertidal Abiotic Conditions
Air, Temperature and Salinity
Desiccated : A term referring to an organism that
has lost its body moisture.
In order to survive, creatures must be able to
either endure the dry time or have a mechanism
to counter it.
Organisms hiding under rocks and crevices and
where water is pooled. (Tidal Pools)
• Some organisms are able to protect
themselves against desiccation by
capturing or sealing in moisture.
• These organisms have shells or other
protective coverings to trap the moisture.
See page 214
• Besides becoming desiccated, intertidal
organisms face challenges of
temperature and salinity fluctuations.
Wave Action
• See figure 9.4 on page 216
• Figure 9.5 on page 217
Zonation
One of the most striking features in an
intertidal area is the noticeable horizontal
bands of organisms exposed at low tide.
These bands can be seen on rocky shores
nearly everywhere in the world.
The bands are made up of similar organisms
located at a specific height are not typically
found anywhere else in the ecosystem.
Vertical Zonation
• is defined at the noticeable horizontal
bands of organisms living within a certain
range in the intertidal zone.
3 Major Zones of the Rocky
Intertidal
• Upper intertidal- sometime called the splash zone, because
it rarely is covered with water.
• Middle intertidal – is filled with an abundance of species.
This area is regularly covered and uncovered with the
tides. Great quantity of Algae.
• Lower intertidal – is an area that is underwater most of the
time. This allows slow moving predators such as sea stars
and snails to almost constantly feed. This zone contains
the largest diversity of organisms.
• See figure 9.7 page 220. Page 226 summary
YouTube
• BBC: Race against the tide, Risking death
against huge blocks of ice.
• http://youtu.be/Z0qGvC3vqaA
• http://youtu.be/u64ppKBY3cM
• http://youtu.be/renpnyTX-mc
• Intertidal Zones
• http://youtu.be/g7Rlh5sA8WE
Lab: Intertidal Zone Organism
Identification and Classification
Observations: Specimen found and Zone
Sea Squirt:
Upper and lower zone
Algae:
Upper, middle and lower
Shrimp:
middle and lower
Blue Crab:
middle and lower
Juvenile lobster:
lower
Mud crab:
middle and lower
Spider crab (male):
middle and lower
Minnows:
lower
Sand flea: amphipod
upper – attached to sea grass
Pike fish:
lower
Lightening Welk:
lower
Ascidian:
upper attached to wall or rocks
Stone crab:
middle and lower
Pistol Shrimp
middle and lower
Arrow Shrimp
middle and lower
Hermit crab
middle and lower
Mussels
middle and lower
Homework
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Finish reading Module 9 to page 232
OYO Questions 9.13 – 9.17
Study Guide: Define e-h and 19-28
Finish lab
Class challenge
Quiz: Rocky Intertidal Zones: See OYO
question 9.11 and 9.12; Abiotic Conditions of
Intertidal zones. Be able to name 15 different
species living in the Intertidal Zone