Intertidal Zonation

INTERTIDAL ZONATION Robert Perry UCLA OceanGLOBE

High Tide Line

THE INTERTIDAL ZONE

Low Tide Line

THE INTERTIDAL ZONE: A zone of life between the high tide line and the low tide line on any beach.

High tide line

Low tide line

INTERTIDAL ZONATION Distinct bands of life consisting of separate communities of organisms distributed from the high tide line to the low tide line.

Illustration: Stephenson & Stephenson (1972)

High tide line

INTERTIDAL ZONATION Increase in abundance and diversity of life as you move seaward. (more ocean water = more ocean life)

Low tide line

Illustration: Stephenson & Stephenson (1972)

Major environmental factors controlling intertidal zonation: MAJOR FACTOR

1. Tides

MAJOR FACTOR

2. Waves

MAJOR FACTOR

3. Slope

MAJOR FACTOR

4. Substrate

very low tolerance

very high tolerance

Among all of the factors that control intertidal zonation, one common point stands out: Organisms differ in their ability to survive.

There is a “normal curve� that represents the range of tolerance of organisms to each ____________________ environmental factor.

MAJOR FACTOR

1. TIDES

What are TIDES ?

Tides are the regular and predictable variations in sea level. ...that correspond to changes in the relative positions of the Moon and the Sun.

MAJOR FACTOR

1. TIDES

Q. What type of tide do we have here in southern California ?

(Calendar courtesy of Tidelines, Inc)

A. mixed semidiurnal tide.

Two unequal HIGH tides, and

(Calendar courtesy of Tidelines, Inc)

Two unequal LOW tides a day.

MAJOR FACTOR

1. TIDES

Exposure to air causes bands or zones of life along the beach.

Intertidal Zone

Total Exposure to Air Hours per Year

Zone 1

High Intertidal

7,200 - 8,760

Zone 2

Upper-Middle

3,200 - 7,200

Zone 3

Lower-Middle

400 - 3,200

Zone 4

Low Intertidal

0 - 400

Data modified from Hedgepeth, Ricketts and Calvin (1968)

MAJOR FACTOR

1. TIDES

MAJOR FACTOR

1. TIDES Zone: 1

Southern California rocky shore dominant species: Name: Splash

Species: snails

2

Upper-mid

barnacles

3

Low-middle

mussels

4

Low

algae

snails barnacles

mussels

algae

Intertidal Zones at La Jolla, California

Stephenson & Stephenson (1972)

MAJOR FACTOR

1. TIDES Alternate exposure to air and water caused by the TIDES results in intertidal organisms occupying specific zones according to their range of tolerance to dryness, temperature, predation, feeding, respiration and reproduction. This pattern can be observed world wide.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

a. Activity cycles & interspecific competition

SUBFACTOR

b. Desiccation

SUBFACTOR

c. Temperature

SUBFACTOR

d. Terrestrial & atmospheric forces

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

a. Activity cycles & interspecific competition

Most intertidal activities are carried out HIGH TIDE during ____________periods.

(Life functions occur better under water).

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

a. Activity cycles & interspecific competition

Prey survive in areas beyond the range of tolerance of their predators.

Example: distribution of mussels.

Snail zone High tide line Barnacle zone young, little mussels Mussel zone old, large mussels

Algae zone

Intertidal zonation on a pier piling Low tide line

High tide line young, little mussels - above the range of Pisaster

range of Pisaster determined by the tides - it cannot move up farther or it cannot get back down to the water line at low tide.

old mussels too large to be eaten by Pisaster

Pisaster

Low tide line

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

b. Desiccation

desiccation The term _____________means to lose vital body fluids and dry up due to exposure to the atmosphere.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

b. Desiccation

There is a range of tolerance to desiccation among intertidal _______________ organisms.

Those that lose fluids fast live in lower zones.

Barnacles, Balanus sp., can close up tight to prevent water loss. Thus they survive in the_______ upper intertidal zones.

Algae, and the sea star, Pisaster sp., tend to dry out easily. Thus they survive in the_______ low intertidal zones.

The sea anemone, Anthopleura, closes up tight and has bits of rocks and shells glued to its body.

It also lives in moist crevices in the low __________ intertidal.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

c. Temperature

One of the most significant features of high heat capacity the sea is its ____________________, its resistance to temperature change.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

c. Temperature

high tide temperatures are uniform At _________, low tide temperatures and stable. At _________, can fluctuate widely.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

c. Temperature

There is a range of tolerance to temperature among intertidal _______________ organisms.

Organisms with a wide range of temperature upper tolerance tend to live in_________zones.

HIGH TIDE Organisms covered by water of uniform and stable temperature.

LOW TIDE Organisms exposed to air, sun, wind and other widely variable forces.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

d. Terrestrial & atmospheric forces

There is a range of tolerance to Terrestrial & atmospheric forces among _____________________ intertidal organisms.

MAJOR FACTOR

1. TIDES Sub-factors that are caused by TIDES : SUBFACTOR

d. Terrestrial & atmospheric forces

LOW tide to such forces Exposure at _______ as hot sun, snow, wind, rain, as well as surviving terrestrial predators such as racoons, crows, coyotes and humans may effect the distribution of organisms.

MAJOR FACTOR

1. TIDES

REVIEW !

Sub-factors that are caused by TIDES : SUBFACTOR

a. Activity cycles & interspecific competition

SUBFACTOR

b. Desiccation

SUBFACTOR

c. Temperature

SUBFACTOR

d. Terrestrial & atmospheric forces

MAJOR FACTOR

2. WAVES

MAJOR FACTOR

2. WAVES Sub-factors that are caused by WAVES: SUBFACTOR

a. Wave shock

SUBFACTOR

b. Increased submergence

MAJOR FACTOR

2. WAVES Sub-factors that are caused by WAVES: SUBFACTOR

a. Wave shock

pounding Wave shock is the _____________ and shearing force ______________of the water as it rushes across the intertidal organisms.

SUBFACTOR

a. Wave shock

Imagine you were an intertidal organism living‌.

HERE !

MAJOR FACTOR

2. WAVES Sub-factors that are caused by WAVES: SUBFACTOR

b. Increased submergence

Waves add water time to the intertidal zone.

MAJOR FACTOR

2. WAVES The principle of vertical displacement

Left side = protected beach Right side = exposed beach

MAJOR FACTOR

2. WAVES Sub-factors that are caused by WAVES: SUBFACTOR

b. Increased submergence

Intertidal zones are expanded and shifted exposed to waves upward on beaches _________________ as compared to beaches protected from waves _____________________.

MAJOR FACTOR

2. WAVES

REVIEW !

Sub-factors that are caused by WAVES: SUBFACTOR

a. Wave shock

SUBFACTOR

b. Increased submergence

MAJOR FACTOR

3. SLOPE of the beach.

The term _________refers slope to the angle at which the sea meets the substrate.

The intertidal zone may vary from shear vertical cliffs, rock faces and pier pilings with an effective slope 90O of______, to broad sand or mud flat region which is nearly horizontal, a slope nearly_____.

0O

MAJOR FACTOR

3. SLOPE of the beach.

0O slope

45O slope

90O slope

MAJOR FACTOR

3. SLOPE of the beach.

The slope of a beach may widen vertical horizontal zones on a__________beach or compress zonation on a_________beach. vertical Associated factors which may be influenced by beach slope include the effects of wave action, submergence time, various types of interspecific predation, competition for living space, and the settlement of larvae.

MAJOR FACTOR

3. SLOPE of the beach.

Slope and zonation.

Note narrow zones as beach nears vertical, and wide zones as beach nears horizontal.

MAJOR FACTOR

4. SUBSTRATE TYPE

Rocky shore

Sandy shore

Beaches are made of different materials.

MAJOR FACTOR

4. SUBSTRATE TYPE Sub-factors that are caused by the SUBSTRATE TYPE: SUBFACTOR

a. Attachment of larvae

SUBFACTOR

b. Porosity of substrate

SUBFACTOR

c. Movement of substrate

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

a. Attachment of larvae

Many larvae have the ability to detect the substrate type and may delay their settlement until a preferred substrate type has been reached.

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

a. Attachment of larvae

The substrate type thus determines where larvae settle out, attach and grow. This helps shape the intertidal zones.

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

b. Porosity of the substrate.

If an organism requires more moisture, it may survive on rock surfaces which are porous and may die on surfaces which are not so porous.

Different substrates hold different amounts of water.

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

b. Porosity of the substrate.

The porosity, or amount of space within a substrate, determines the amount of water that substrate can hold.

This accounts for different patterns of zonation on beaches with different kinds of substrates !

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

c. Movement of the substrate.

The success of many intertidal organisms is directly related to the frequency of substrate movement. If the substrate moves or shifts around regularly, it is a less stable environment for sessile and motile forms alike.

Diameter of rock (cm) Average number of movements per year SUBFACTOR

Movement of the substrate.

MAJOR FACTOR

4. SUBSTRATE TYPE SUBFACTOR

c. Movement of the substrate.

larger The________the substrate particle, the less often it moves.

The less often it moves, more the________stable the environment.

REVIEW !

MAJOR FACTOR

4. SUBSTRATE TYPE Sub-factors that are caused by the SUBSTRATE TYPE: SUBFACTOR

a. Attachment of larvae

SUBFACTOR

b. Porosity of substrate

SUBFACTOR

c. Movement of substrate

CONCLUSION: we have studied in detail the major environmental factors controlling intertidal zonation: MAJOR FACTOR

1. Tides

MAJOR FACTOR

2. Waves

MAJOR FACTOR

3. Slope

MAJOR FACTOR

4. Substrate