15
____________________________________________________________________________________________
CORAL REEF COMMUNITIES
Chapter Outline
REEF CORALS AND THE FORMATION
OF REEFS
Coral Colonies
Coral Nutrition
Reproduction in Coral
Source of Nutrients
Photosynthesis on Reefs
Reef Productivity
THE CORAL REEF COMMUNITY
Other Symbiotic Relationships
ADAPTATIONS AMONG REEF
DWELLERS
Adaptive Behaviors to Avoid Predation
Structural Adaptations for Feeding
Effects of Human Activities
Destructive Fishing Practices
Coastal Development
Other Human Activities
Chapter Objectives
• Describe the general characteristics of coral reefs including the major organisms
that make up a reef community and the structures of various types of reefs.
• Identify the locations of coral reefs around the world.
Key Terms
zooxanthellae
scleractinian coral
hermatypic
patch reefs
bank reefs
reef front
surge channels
reef flat
gross primary production
Chapter Summary
2. Stony (or true) corals are colonial organisms that produce the calcium carbonate
deposits that make up most of the structure of a coral reef. Together with algae, they
3. Corals reproduce both asexually and sexually. Many coral species are
4. Coral reefs are constantly forming and breaking down, a process known as
bioerosion. Boring organisms weaken the bases of large coral stands, causing them to
5. There are three basic types of reefs. The three reef types share many similarities in
their basic structure. Because of differences in the physical environment, each area of
6. Indo-Pacific reefs are of greater antiquity, have a greater diversity of organisms,
have more extensive algal ridges, grow to 60 meters or less in depth, have a far
Chapter 15 159
7. Despite existing in nutrient-poor tropical ocean water, coral reefs are one of the most
productive of all ecosystems. Reef photosynthetic organisms include the
8. Where corals flourish, so do large numbers of other organisms. The corals not only
9. Competition is very prevalent because space and light are limited. Corals also
compete with other reef organisms, each with their own aggressive and defensive
10. Most fish are carnivores. How so many fish species coexist on coral reefs without
being excluded by competition is a source of debate.
12. The reef is a huge complex full of intricate interdependencies. These intimate
13. The health of coral reefs is affected by both physical and biological phenomena.
Coastal development has a detrimental effect, increasing runoff and nutrient load,
Chapter Outline
I. Coral Reefs and the Formation of Reef Organisms that Build Coral Reefs
A. Coral colonies.
B. Coral nutrition.
C. Reproduction in coral.
D. Reef formation.
1. Impact bubble: the effect of atmospheric carbon dioxide levels on coral reefs.
160 Coral Reef Communities
II. Structure of Coral Reefs
A. Reef types.
VI. The Coral Reef Community
A. Competition between corals and other reef organisms.
B. Competition among reef fishes.
C. Effects of grazing.
D. Effects of predation.
E. Symbiotic relationships.
1. Use of color for concealment and protection.
2. Other roles of color.
VIII. Threats to Coral Reefs
A. Why are coral reefs important?
B. Effects of human activities.
1. Destructive fishing practices.
Suggestions for Presenting the Material
1. Provide samples of various stony corals (brain, branching, leaf, foliose) so students
can compare morphological differences as they relate to habitat. Where would each
species be found on the reef, and why?
2. A saltwater aquarium can serve to represent a coral reef in microcosm; however, be
3. Ask students if any of them have visited a coral reef. If so, what do they most
Classroom Discussion Ideas
1. Explain Darwin’s theory of the formation of fringing reefs, barrier reefs, and atolls.
2. Contrast several ways in which coloration in coral reef fish differs from that seen in
epipelagic fish.
3. How are offshore coral reefs affected by loss of mangroves on land? What is the
functional relationship that connects these habitats?
4. What are several steps that we as individuals can take to contribute to the
preservation of coral reefs? Discuss involvement on local, national, and international
scales.
Videos, Animations, and Websites
Video
Coral Reefs: A Comprehensive Overview. (CD-ROM, 2004)
Interactive CD-ROM contains hundreds of color photos of reef organisms, plus
diagrams, tables, graphs, phylogenetic trees, maps of global reef distribution, and a
geologic timeline of marine community development. Divided into six main sections
Treasures of the Great Barrier Reef. (DVD, NOVA, 60 min, 1995)
Coral Reef Adventure. (DVD, 2003)
Follows an expedition to document the health of coral reefs around the South Pacific.
The Living Sea. (DVD, PBS, 1995)
Animations
Virtual World—Great Barrier Reef. (National Geographic)
An interactive reef ecosystem that describes the various species on the Great Barrier
Websites
World Wildlife Foundation.
Explains the international initiatives and legal work being done to protect marine
http://wwf.panda.org/about_our_earth/blue_planet/coasts/coral_reefs/
Global Coral Reef Alliance.
Maintains a current list of reef issues from the popular press.
Reef Relief.
Nonprofit organization dedicated to increasing awareness of coral reef issues,
ReefBase.
A global clearinghouse for monitoring, restoration, and management projects.
Suggested Answers to End of Chapter Questions
Multiple Choice
1. a. a barrier reef
2. b. reef front
Matching
1. g.
6. d.
11. j.
Short Answer
1. What roles do coralline and calcareous algae play in reef formation?
Calcareous erect algae have an important role in generating CaCO3 deposits on the
2. Explain how the physical characteristics of the reef environment influence the species
of coral that inhabit them.
Physical characteristics of the reef environment (most importantly, the frequency
3. Describe how a coral colony is formed.
A coral colony is formed when a coral larva (planula) settles out of the plankton
4. Describe the process of reef formation.
The process of reef formation comprises alternating phases of constructive and
5. Describe how an atoll is formed.
Atolls form as rings of reef around an extinct volcano that is eventually eroded by
164 Coral Reef Communities
6. If the water surrounding coral reefs is nutrient poor, how can the coral reef support
large numbers of organisms?
Despite being in nutrient-poor waters, coral reefs are highly productive and
7. Describe what is meant by a cleaning symbiosis.
In cleaning symbiosis, the host benefits from the removal of parasites and dead
8. Why don’t most coral species grow in the aphotic zone?
9. Why are coral reef fishes so brightly colored?
The adaptive value of color in reef fishes is thought to serve both communication
10. Why is moderate wave action important to the health of the reef?
Moderate wave action is important because it removes sediments from sensitive
Thinking Critically
1. How does the practice of using cyanide to collect aquarium fish affect corals and other
reef organisms?
2. What impact would daily visits by hundreds of sport divers and snorkelers have on a
reef community?
High levels of human visitation on a coral reef are associated with the following:
Chapter 15 165
3. Why are coral reefs not found along warm coastal areas where large rivers such as the
Mississippi, Amazon, and Congo empty into the sea?
4. Coral reefs are generally confined to the tropics, defined as the area between 23.4
degrees N and S latitudes. Yet coral reefs exist in Bermuda, which lies at 32 degrees
N latitude. How is this possible?
Warm water is brought to Bermuda via the Gulf Stream Current. In addition, the
5. What factors account for the small number of atolls in the Atlantic Ocean versus those
in the Indo-Pacific?
Suggestion InfoTrac® Articles
“How Much Time Can Herbivore Protection Buy for Coral Reefs under Realistic
Regimes of Hurricanes and Coral Bleaching?” Edwards, H.J., I.A. Elliot, C.M. Eakin, A.
Irikawa, J.S. Madin, M. McField, et al. Global Change Biology, (2011).