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INTERTIDAL COMMUNITIES
Chapter Outline
ROCKY SHORES
Adaptations to Life on Rocky Shores
Avoiding Overheating and Desiccation
Coping With Cold
Avoiding Wave Shock
Rocky Shore Zonation
Temperate Rocky Shores
Ecological Succession in the Intertidal
Zone
Intertidal Fishes
SANDY BEACHES
Meiofauna
Factors Affecting the Distribution of
Meiofauna
Chapter Objectives
• Describe the general adaptations of rocky intertidal organisms to the physical
factors of their habitat.
• Identify various zones of intertidal communities of temperate and tropical rocky
shores.
• Recognize the importance of tide pools as refuge during low tides.
Key Terms
active continental margins
climax community
dissipative beaches
Chapter Summary
1. Intertidal organisms must survive in complex habitats that are alternately exposed
2. Rocky shores are inhabited by many organisms that tend to form bands, or zones, on
3. The tropical midlittoral is divided into yellow and pink zones, due to the presence of
4. Tide pools are refuges for organisms during periods of low tide, though chemical
and physical variables can fluctuate widely, making the tide pool a potentially
5. In addition to physical factors, biotic factors such as grazing, predation, and
6. The distribution and type of organisms found on sandy shores are greatly influenced
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7. The meiofauna are the microscopic organisms that live among the sand grains and
Chapter Outline
I. Rocky Shores
A. Adaptations to life on rocky shores.
B. Rocky shore zonation.
1. Temperate rocky shores.
2. Tropical rocky shores.
3. Comparison of temperate and tropical rocky intertidal systems.
C. Tide pools.
D. Impact bubble—Human disturbance in the intertidal.
E. Living on the rocky shore.
1. Competition, grazing, and predation.
2. Variation in larval settlement (recruitment).
3. Positive interactions among species.
4. Ecological succession in the untertidal zone.
F. Intertidal fishes.
G. Ecology of the rocky shore.
3. Ecological succession in the intertidal zone.
II. Sandy Shores
A. Role of waves and sediments.
B. Living in the sandy intertidal.
C. Tides and the activity of organisms.
Suggestions for Presenting the Material
1. If the students are near a coast, arrange for a field trip to the intertidal zone or to a
local aquarium where your class can observe local species.
2. If the students live in a coastal state, have students create a shell collection of local
3. Have students bring to class samples of beach sand collected from various locations.
4. Have students create a concept map using intertidal communities as the starting
point that connects the following terms: biotic interactions, competition, lower limit
Classroom Discussion Ideas
1. Which is a more physically stressful habitat, the sandy beach or the rocky shore?
Compare several abiotic aspects of both habitats to support your opinion.
2. Describe the feeding methods of rocky intertidal organisms. How do those methods
differ from animals that live in a sandy beach?
3. Contrast the upper and lower intertidal zones in terms of the major species found in
each and the dominant physical conditions that affect those organisms.
4. What is the ecological importance of meiofauna? If they were to become absent from
sandy beaches, what effects might be seen and why?
Videos, Animations, and Websites
Videos
The Living Planet 7: Margins of Land. (DVD, 50 min, 2004, original broadcast 1984)
David Attenborough leads viewers on a journey exploring the lives of intertidal
organisms around the globe.
Planet Earth: Shallow Seas. (set of five DVDs, BBC, 2007)
Spectacular time-lapse photography illustrates several intertidal areas.
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The Blue Planet: Seas of Life (Tidal Seas/Coasts). (set of five DVDs, BBC, 2002)
David Attenborough narrates this Emmy-award winning documentary examining
marine life in shallow coastal regions.
Ecology: Life at the Edge of the Sea. (DVD, 25 min, 2001)
Discusses the environmental stresses faced by rocky intertidal organisms, and illustrates
the diversity of adaptations shown by shoreline and tide pool animals to survive in this
Life on the Edge: A Guide to Pacific Coastal Habitats. (DVD, 35 min, 2008)
Explores key coastal habitats from Alaska to California, including sandy beach, eelgrass
Websites
Global Warming and Our Coasts.
Flash animation provides an overview of global warming’s effects on coastal shoreline
American Field Guide: Ocean Habitats: The Intertidal Zone.
Online video segments illustrating principles of rocky shore ecology, along with teacher
Multi-Agency Rocky Intertidal Network.
A website profiling 25 years of data collected on rocky intertidal zones of the United
Office of National Marine Sanctuaries—Sanctuary Integrated Monitoring Network.
Summary of ecological and monitoring information for numerous types of coastal
habitats within the California current ecosystem; examples serve as useful case studies
for teachers in other states.
146 Intertidal Communities
Suggested Answers to End of Chapter Questions
Multiple Choice
1. d. All the above factors determine the width of intertidal zones.
2. c. periwinkle
Matching
1. a.
1. e.
Short Answer
1. Describe some of the adaptations exhibited by organisms inhabiting rocky coasts that
help them survive wave shock.
Adaptations to help reduce the effects of wave shock include: flexible bodies
2. Explain how knobby periwinkles avoid desiccation.
Knobby periwinkles reduce the effects of exposure and desiccation by having a
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3. What environmental challenges do tide pool organisms encounter during the tidal
cycle?
Environmental challenges faced by tide pool organisms include: temperature and
decreases in dissolved oxygen concentration.
4. Compare the vertical zonation on a rocky shore to that of a sandy beach.
The vertical zonation of a sandy beach is less apparent than the obvious zonation
of a rocky shore. Sediment composition of a sandy shore influences degree of
water retention, affecting vertical distribution of organisms in the sediment
column. Rocky intertidal habitats provide a stable substrate on which to grow and
Thinking Critically
1. Do you think pollutants entering from the ocean would have a greater effect on rocky
shores or on sandy shores? Explain your answer.
Pollution may have less effect on sandy shores than on rocky shores, because the
composition on rocky shores.
148 Intertidal Communities
2. What abiotic factor is probably most important in terms of influencing the number of
organisms that can inhabit a rocky shore?
While there is no one correct answer to this question, with all other factors being
3. What kinds of organisms that inhabit sandy shores would be least affected by the
recreational use of beaches?
Sandy beach meiofaunal organisms would be least affected by human recreational
Suggested InfoTrac® Articles
“Regulation of Intertidal Food Webs by Avian Predators on New England Rocky
Shores.” Ellis, J.C., M.J. Shulman, M. Wood, J.D. Witman, and S. Lozyniak. Ecology,
(2007).