1. Chapter 9
Coral Reefs
Coral reefs are living structures that provide homes and
attachment sites for countless marine organisms in shallow
tropical oceans.

2. Coral Reefs
Anatomy and Growth
 Coral reefs are created by many species of
colonial cnidarians.
 These anemone-like polyps produce a
CaCO3 skeleton in a great variety of sizes
and shapes.

3. Coral Reefs
Anatomy and Growth
© Photos.com
Fig. 9.1 Extended polyps of a coral colony. The
numerous light-colored spots on the tentacles are
batteries of cnidocytes.
Fig. 9.2 Cross-section of a coral polyp and a
calcareous corallite skeleton. The living coral tissue
forms a thin interconnection, the cenosarc, over the
surface of the reef.

4. Coral Reefs
Anatomy and Growth
Fig. 9.3 Coral exhibit a large variety of growth forms.

5. Coral Reefs
Anatomy
and Growth
Fig. 9.4 Parrotfishes, major
grazers of coral skeletal
material, use their powerful
jaws to produce large
amounts of carbonate sand
on the reef.
© Wolfgang Amri/ShutterStock, Inc.

6. Coral Reefs
Coral Distribution
 Living coral reefs usually are located:
• within 30º latitude of the equator
• in water that averages at least 20ºC
• on the eastern sides of most continents
• within the photic zone at depths of 0-50 meters

7. Coral Reefs
Coral Distribution
Fig. 9.5 Distribution of reef-forming corals, by number of
genera. Heavy black lines indicate continental barrier reefs.
Light blue: <20 genera
Medium blue: 20-40 genera
Dark blue: > 40 genera

8. Coral Reefs
Coral Ecology
 Reef-building corals maintain a mutualistic
relationship with a dinoflagellate called
zooxanthellae
 The alga provides photosynthetic products to the
coral to aid in its survival and growth
 The alga receives unlimited carbon dioxide and
nitrogenous wastes from the coral polyp in a
competition-free setting

9. Coral Reefs
Coral Ecology
Fig. 9.6 Exchange of materials between zooxanthellae and their coral host.

10. Coral Reefs
Coral Reef Formation
 Charles Darwin was the first to suggest that
coral reefs are sequential developmental
stages in the life cycle of a single reef:
• fringing reefs
• barrier reefs
• atolls

11. Coral Reefs
Fig. 9.7 A satellite view of a
portion of the hundreds of atolls
that make up the nation of
Maldives.
Courtesy of NASA Earth Observatory

12. Coral Reefs
Fig. 9.8 The developmental sequence of coral reefs, from young fringing reefs (left), to
barrier reefs (center), and finally to atolls (right).

13. Coral Reefs
Coral Reef Formation and Hot Spots
Fig. 9.9 Chains of
volcanoes along the
Hawaiian IslandEmperor Seamount
are carried, in a
conveyer-belt
fashion, north into
deeper water by the
movement of the
Pacific Plate. Each
volcano was formed
over the “hot spot,” a
continuous source of
new molten material
presently under
Hawaii, and is carried
to its eventual
destruction in the
Aleutian Trench.
Courtesy of NGDC/NESDIS/NOAA

14. Coral Reefs
Reproduction in Corals
 Corals reproduce in a great variety of ways,
both asexually and sexually
 Most sexually reproducing corals are
hermaphroditic spawners

15. Coral Reefs
© Gary Bell/OceanwideImages.com
b
Fig. 9.10 Spawning corals. (a) Female brain coral
releasing eggs; (b) male mushroom coral releasing sperm.
a
© Marty Snyderman/Visuals Unlimited

16. Coral Reefs
Fig. 9.11
Micrograph of a
planula larva of
the coral
Pocillopora.
© Valerie Hodgson/Visuals Unlimited

17. Coral Reefs
Zonation on Coral Reefs
 Wave force, water depth, temperature, salinity,
and a host of biological factors vary greatly across
a reef
 Together they result in both horizontal and vertical
zonation of the species that form the reef

18. Coral Reefs
Zonation on
Coral Reefs
Fig. 9.12 Cross-sectional
zonation of a barrier reef.

19. Coral Reefs
Fig. 9.13
Echinometra, a
common tropical
sea urchin.
© Ewen Cameron/ShutterStock, Inc.

20. Coral Reefs
Fig. 9.14 A giant clam, Tridacna, amid
mixed corals. Note the blue mantle
tissue that is brightly colored due to the
presence of innumerable mutualistic
zooxanthellae.
© Andy Lim/ShutterStock, Inc.

21. Coral Reefs
Fig. 9.15 Variations in coral
growth forms: (a) table coral,
Acropora; (b) brain coral,
Diploria; and (c) staghorn
coral, Acropora.
a
© Andy Lim/ShutterStock, Inc.
© Andy Lim/ShutterStock, Inc.
Zonation on
Coral Reefs
© Lawrence Cruciana/ShutterStock, Inc.
b
c

22. Coral Reefs
Coral Diversity and Catastrophic Mortality
 Reefs worldwide are threatened by human
activities, succumbing to:
• pollution
• destructive fishing practices
• bleaching
• a host of diseases

23. Coral Reefs
b
a
Courtesy of AIMS/NOAA
Courtesy of David Burdick/NOAA
Fig. 9.16 The predatory sea star, Acanthaster, and (b) its major predator, the Pacific triton, Charonia.

24. Coral Reefs
Coral Diversity and Catastrophic Mortality.
Courtesy of Dr. Phillip Dustan, College of Charleston
Fig. 9.17 Black band disease overgrowing a coral
head. This star coral, Montastrea, which could be as
much as 500 years old, will probably be dead within
one year.
Courtesy of David Burdick/NOAA
Fig. 9.18 Wide-spread bleaching on a Pacific coral
reef.

25. Coral Reef Fishes
Fig. 9.19 Some common reef fishes on
a tropical Caribbean reef:
1. nurse shark (Ginglymostoma),
2. reef shark (Carcharhinus),
3. barracuda (Sphyraena),
4. surgeonfish (Acanthurus),
5. butterflyfish (Chaetodon),
6. angelfish (Pomacanthus),
7. hawkfish (Amblycirrhitus),
8. grouper (Mycteroperca),
9. moray eel (Gymnothorax),
10. stingray (Dasyatis),
11. grunt (Haemulon),
12. soldierfish (Myripristis),
13. porcupinefish (Diodon).
Angelfish photo from Joyce and Frank Burek/NOAA; all other photos from John Morrissey

26. Coral Reef Fishes
Coral Reef Sharks and Rays
 Reefs worldwide are dominated by:
• benthic orectolobid sharks (nurses, wobbegongs, and
bamboosharks)
• and more typical pelagic carcharhinid sharks (blacktips,
whitetips, tigers, and reef sharks)

27. Coral Reef Fishes
Coral Reef Sharks and Rays
Fig. 9.20 Dermal flaps around the mouth of a wobbegong, a benthic reef shark.

28. Coral Reef Fishes
Coral Reef Teleosts
 About 50% of all
living vertebrates
are teleost fishes,
and many of these
fishes inhabit coral
reefs.
Courtesy of NOAA
Fig. 9.21 Numerous species of teleost fishes are associated
with coral reefs.

29. Coral Reef Fishes
Coral Reef Teleosts
 The great diversity of teleost fishes have
evolved numerous symbiotic relationships
such as inquilinism and cleaning behaviors.

30. Coral Reef Fishes
Fig. 9.22 Two remoras,
Echeneis, with modified
dorsal fins accompanying
a nurse shark,
Ginglymostoma.

31. Coral Reef Fishes
Coral Reef Teleosts
© Russell Swain/ShutterStock, Inc.
Fig. 9.24 A clownfish, Amphiprion, nestled within the
protective tentacles of its host anemone.
Fig. 9.23 Shrimpfish, Aeoliscus, seeking
shelter amid the spines of a sea urchin.

32. Coral Reef Fishes
Coral Reef Teleosts
Courtesy of Dr. Anthony R. Picciolo, NOAA NODC
Fig. 9.25 A nearly transparent cleaner shrimp,
Periclimenes, on a Caribbean sponge.
© Kelpfish/ShutterStock, Inc.
Fig. 9.26 Neon gobies, Elacatinus, clean the head of a
large green moray, Gymnothorax.

33. Coral Reef Fishes
Coral Reef Teleosts
 The brightly colored patterns of coral reef fishes
illustrate the advertisement, disguise, and
concealment roles of brilliant coloration in a coral
reef environment.

34. Coral Reef Fishes
Coral Reef Teleosts
© Frank Boellmann/ShutterStock, Inc.
© Rene Frederic/age fotostock
Fig. 9.27 A well-camouflaged scorpionfish, Scorpaena (left),
with magnified chromatophores from a section of skin (right).

35. Coral Reef Fishes
Coral Reef Teleosts
© Lawrence Cruciana/ShutterStock, Inc.
© cbpix/ShutterStock, Inc.
Fig. 9.28 Disruptive coloration patterns of two species of butterflyfishes, Chaetodon.

36. Coral Reef Fishes
Fig. 9.29 A cleaner
wrasse, Labroides
(above), and its mimic,
Aspidontus (below).

37. Coral Reef Fishes
Coral Reef Teleosts
 About one fourth of all reef-fish species place
sticky benthic eggs in a guarded nest on the reef.

38. Coral Reef Fishes
Coral Reef Teleosts
© David Fleetham/Alamy Images
Fig. 9.31 A sergeant major (Abudefduf) guards its
purple egg mass in the Caribbean Sea.
Courtesy of Dr. Michael P. Robinson
Fig. 9.30 Two bicolor damselfish mate inside a
discarded PVC pipe on a Caribbean reef.

39. Coral Reef Fishes
Coral Reef Teleosts
 Most reef teleosts are pelagic spawners.
 As many as 30 or more species at any given time
will assemble around a coral promontory to
broadcast as many as 50,000 eggs apiece into the
water column.
 After fertilization, these pelagic eggs drift away
from the reef and disperse for one day to a year or
more.

40. Coral Reef Fishes
Coral Reef Teleosts
Fig. 9.32 Dog snappers, Lutjanus jocu,
return to the reef after a spawning run in
the water column off Belize.
© Doug Perrine/Seapics.com

47. Coral Reef Fishes
Fig. 9.33 Locations of U.S. National Marine Sanctuaries
and National Estuarine Research Reserves.

48. Coral Reef Fishes
Coral Reef Teleosts
 The great diversity of
reef fishes results in
sexual systems that
range from species
with separate sexes to
simultaneous and
sequential
hermaphrodites.
© WaterFrame/Alamy Images
Fig. 9.34 Clasping hamlets above a reef.

49. Coral Reef Fishes
Coral Reef Teleosts
Courtesy of Dr. Michael P. Robinson
Courtesy of Dr. Michael P. Robinson
Fig. 9.35 Male and female “bluehead” wrasses in
their initial yellow phase.
Fig. 9.36 Terminal-phase bluehead male surveying his
territory.

50. Coral Reef Fishes
Fig. 9.37 Relative reproductive success experienced by males and females of protandrous clownfishes (left)
and protogynous wrasses (right).