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Chapter 9
Tropical and
Subtropical
Shallow Seas
Coral reefs, mangrove
stands, and seagrass
meadows provide homes
and attachment sites for
countless marine organisms
in shallow tropical oceans.
Copyright © 2004 Jones and Bartlett Publishers
Chapter 9
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.
Chapter 9
Coral Reefs
•Anatomy and Growth
Fig. 9.1 Extended polyps of a
coral colony. The numerous
light-colored spots on the
tentacles are batteries of
cnidocytes (Courtesy of T. Phillipp)
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
Coral Reefs
•Anatomy and Growth
Fig. 9.3 Coral exhibit a large variety of growth forms.
Chapter 9
Chapter 9
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
Chapter 9
Coral Reefs
•Coral Distribution
Fig. 9.5 Distribution of reef-forming corals, by
number of genera. Black lines indicate
continental barrier reefs.
Light blue <20 genera
Medium blue 20-40 genera
Dark blue > 40 genera
Chapter 9
Coral Reefs
•Coral Ecology
– Reef-building corals contain a mutualistic
single-celled dinophyte that provides
photosynthetic products to the coral to aid in
its survival and growth.
Chapter 9
Coral Reefs
•Coral Ecology
Fig. 9.6 Exchange of materials between zooxanthellae and their coral host.
Chapter 9
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
Chapter 9
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).
Coral Reefs
Chapter 9
•Coral-Reef Formation
Fig. 9.9 Volcano chains along the Hawaiian Island-Emperor Seamount are
carried, in a conveyer-belt fashion, north into deeper water by the movement of
the Pacific Plate.
Chapter 9
Coral Reefs
•Reproduction in Corals
– Corals reproduce in a great variety of ways,
both asexually and sexually. Most sexually
reproducing corals are hermaphroditic
spawners.
Chapter 9
Coral Reefs
•Zonation on Coral Reefs
–
Wave force, water depth, temperature,
salinity, and a host of biologic factors vary
greatly across a reef and result in both
horizontal and vertical zonation of the species
that form the reef.
Coral Reefs
Chapter 9
•Zonation on
Coral Reefs
Fig. 9.12 Cross-sectional zonation of an atoll.
Chapter 9
Coral Reefs
•Zonation on Coral Reefs
(a) plate coral, Acropora
(b) brain coral, Diploria
(c) staghorn coral, Acropora
Fig. 9.15 Variations in coral growth forms from the Solomon Islands.
Chapter 9
Coral Reefs
•Coral Diversity and Catastrophic Mortality
– Reefs worldwide are threatened by human
activities, succumbing to pollution, destructive
fishing practices, bleaching, and a host of
diseases.
Chapter 9
Coral Reefs
•Coral Diversity and Catastrophic
Mortality.
Fig. 9.17 External symptoms
of black-band disease on
coral.
Fig. 9.18 Effect of coral bleaching
on a Caribbean coral head.
Coral-Reef Fishes
Fig. 9.19 General
habitats of some
common reef fishes on
a tropical Caribbean
reef.
Chapter 9
Chapter 9
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 reefs sharks).
Coral-Reef Fishes
Chapter 9
•Coral-Reef Sharks and Rays
Fig. 9.20 Dermal flaps around the mouth of a wobbegong, a benthic shark.
Chapter 9
Coral-Reef Fishes
•Coral-Reef
Teleosts
– About 50% of all
living vertebrates
are teleost fishes,
and many of these
fishes inhabit coral
reefs.
Fig. 9.21 Close-up of a small coral head
with some of its many associated fish
species.
Chapter 9
Coral-Reef Fishes
•Coral-Reef Teleosts
– The great diversity of fishes have evolved
numerous symbiotic relationships such as
inquilinism and cleaning behaviors.
Coral-Reef Fishes
Chapter 9
Fig. 9.27a A well-camouflaged scorpionfish, Scorpaena (Courtesy of T. Phillipp).
Chapter 9
Coral-Reef Fishes
•Coral-Reef Teleosts
Fig. 9.24 Clownfishes,
Amphiprion, hovering near their
host anemone (Courtesy of T. Phillipp).
Fig. 9.26 A small wrasse,
Labroides, cleaning external
parasites from a lionfish, Pterois
(Courtesy of C. Farwell).
Chapter 9
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.
Coral-Reef Fishes
Chapter 9
•Coral-Reef Teleosts
(a)
(b)
Fig. 9.28 Disruptive coloration pattern of two species of butterflyfish, Chaetodon
(a. courtesy of T. Phillipp).
Chapter 9
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.
Chapter 9
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.
Coral-Reef Fishes
Chapter 9
•Coral-Reef Teleosts
Fig. 9.35 Male and female
“bluehead” wrasses in their initial
yellow phase.
Fig. 9.36 Terminal-phase bluehead male.
Some Tropical Marine
Tetrapods
Chapter 9
•Tropical Marine Reptiles
– The 100 or so species of sea snakes are closely
related to the highly venomous cobras, coral
snakes, and kraits. Most sea snakes are highly
derived and are able to complete their entire
life cycle at sea, remaining underwater for 8
hours or more.
Some Tropical Marine
Tetrapods
Chapter 9
•Tropical Marine Reptiles
– Most sea turtles (seven species are known)
frequent coral reefs and seagrass meadows,
often navigating over great distances to return
to preferred nesting beaches.
Some Tropical Marine
Tetrapods
Chapter 9
•Tropical Marine Reptiles
Fig. 9.41 The leatherback sea turtle, Dermochelys coriacea.
Some Tropical Marine
Tetrapods
Chapter 9
•Mammalian Grazers of Seagrasses
– Manatees and dugongs are the only
herbivorous marine mammals. They use their
prehensile snouts to graze on a wide variety of
sea grasses and other plants.
Some Tropical Marine
Tetrapods
Chapter 9
•Mammalian Grazers of Seagrasses
Fig. 9.43 The Caribbean manatee manipulating plant
food with its snout vibrissae and flippers.