Learning Center
Plans & pricing Sign in
Sign Out

Coral Reefs


									 Coral Reefs

Marine Science
What are Coral Reefs?
                  Coral Reefs are the
                   "Rainforests" of the ocean.
                  Reefs are ecologically
                   important ecosystems and
                   have a high biodiversity that
                   serves as a storage bank of
                   rich genetic resources.
                  They are a source of food
                   and medicine, and they
                   protect the coast from wave
                  Coral Reefs
The Organisms That Build Reefs

                             Coral reefs are made of
                              vast amounts of calcium
                              carbonate (CaCO3),
                              limestone, that is
                              deposited by living things
                             Corals: Structure and
Reef Corals

               Corals are cnidarians,
                unlike many other
                cnidarians, they lack a
                medusa stage and live
                only as polyps
               In reef-building corals the
                polyps produce calcium
                carbonate skeletons,
                billions of these tiny
                skeletons build a massive
               Not all corals build reefs
The Coral Polyp

                   Coral polyps are not only
                    small, but deceptively
                    simple in appearance,
                    they look much like little
                    sea anemones.
                   They have an upright
                    cylinder of tissue with a
                    ring of tentacles on top,
                      they use these stinging
                       tentacles to catch food,
                       especially zooplankton,
                       the tentacles surround the
The Coral Polyp

                   A single founder polyp
                    lands somewhere on the
                    ocean floor and if it
                    survives, it divides over and
                    over to form the colony,
                    thus all polyps in a coral
                    colony are genetically
                    identical copies of the
                    founder polyp
                   The digestive and nervous
                    systems of the polyps
                    remain connected
The Coral Polyp

                   Nearly all reef-building
                    polyps contain symbiotic
                    zooxanthellae- a
                    dinoflagellate algae
                   These zooxanthellae
                    provide coral with the
                    energy they need to
                    build their CaCO3
                    skeleton, without these
                    zooxanthellae there
                    would be no coral reefs
Coral Nutrition

                   Zooxanthellae perform
                    photosynthesis and pass
                    some of the organic
                    matter they make onto
                    the coral
                   Coral polyps are very
                    efficient at removing
                    zooplankton brought in by
                    currents therefore the
                    reefs have been called a
                    “wall of mouths”
Conditions for Reef Growth

                          Reefs are rare on soft
                           bottoms because coral
                           larvae need to settle on a
                           hard surface
                          Coral Reef Spawning
Light and Temperature
                         Corals can only grow in
                          shallow water, where light
                          can penetrate, because the
                          zooxanthellae need the light
                         Coral reefs are therefore
                          found only on continental
                          shelves, around islands or
                          on top of seamounts
                         Corals also prefer clear
                          waters, so that light can get
                          through, and corals can
                          only reproduce is the
                          average water temperature
                          is above 68 F
                         Where coral reefs are found
Light and Temperature

                         If water to too warm,
                          corals will expel their
                          zooxanthellae, this is
                          called coral bleaching
                          because the corals turn
                          white without their
                          symbiotic zooxanthellae
                         Widespread coral
                          bleaching occurs when El
                          Nino occurs, because it
                          brings warm water to
                          many parts of the ocean
                         Global Warming
Sediments, Salinity, and Pollution

                            Fine sediment, like silt, is
                             very harmful to corals, it
                             clouds the water
                            To remove sediment,
                             corals slough off mucus,
                             which carries the
                             sediment off with it
                            Coral Diseases
Fringing Reefs

                  These are the most common
                   and simplest kind of reef
                  Rocky shorelines provide the
                   best conditions for fringing
                   reefs, these reefs grow in a
                   narrow band or fringe along
                   the shore
                  The longest reef in the world
                   is a fringing reef that runs
                   4000 km (2,500 mi) along the
                   coast of the Red Sea, the
                   climate is dry and no streams
                   bring in sediment or
                  Types of Reefs
Barrier Reefs

                 Barrier reefs also lie
                  along the coast, but occur
                  considerably farther from
                  shore, occasionally as far
                  as 100 km (60 mi) or
                 Barrier reefs are
                  separated from the shore
                  by a relatively deep
Barrier Reefs

                 The largest and most famous
                  barrier reef is the Great Barrier
                  Reef, it runs more than 2,000
                  km (1,200 mi) along the
                  northeastern coast of
                  Australia, it varies in width
                  between15 and 350 km (10
                  and 200 mi)
                 The Great Barrier Reef is
                  actually a system of more than
                  2,500 smaller reefs and
Atoll Structure
                   An atoll is a ring of reef,
                    they can be found far
                    from land, rising up from
                    depths of thousands of
                    meters or more
                   Atolls may be anywhere
                    from one mile across to
                    well over 20 miles
                   Atolls may include a
                    dozen or more islands
                    and be home to
                    thousands of people
                   Atoll are rings of reef,
                    with steep outer slopes,
                    that enclose a shallow
How Atolls Grow

                   An atoll begins as a
                    fringing reef around a
                    volcanic island, as the
                    island slowly sinks, the
                    reef flat gets wider and
                    deeper and eventually
                    becomes a lagoon, at this
                    stage the fringing reef
                    has become a barrier
                    reef, eventually the island
                    sinks altogether, leaving
                    only a ring of living
                    growing reef, an atoll
The Ecology of Coral Reefs

                          Coral reefs are the
                           richest and most complex
                           of all marine ecosystems,
                           thousands of species
                           may live on a reef
                          Coral Diversity
                          Medicine from the Sea
Warm up

What are the three types of Reefs?
 What are some limiting factors for the
 growth and reproduction of coral reefs?
Describe a coral polyp.
Why are Zooxanthellae important to corals?
The Trophic Structure of Coral Reefs

                               Using sunlight,
                                zooxanthellae incorporate
                                nutrients into organic
                                compounds, which are
                                passed on to the coral
                               The waste products of
                                fish can be an important
                                source of nutrients and
                                help the coral grow faster
                               Seaweeds are an
                                important primary
                                producer on the reef, and
                                many fishes, sea urchins,
                                snails, and other animals
                                graze on these seaweeds
               Corals compete for the
                space they need in many
                ways, fast-growing ones
                tend to grow upward and
                then branch out, cutting their
                neighbors off from light
               Other corals actually attack
                their neighbors by digesting
                the tissues of the other
                corals or by stinging them
Predation on Corals

                       A variety of animals eat
                        the corals, they keep the
                        reef in tact by just eating
                        individual polyps or bits
                        and pieces of the reef
                          Ex. Parrotfish, Angelfish
The Crown-of-Thorn Sea Star

                         The crown-of-thorns
                          feeds by pushing its
                          stomach out through the
                          mouth and digesting the
                          coral tissue with the
                         Coral harbors symbiotic
                          crabs, shrimps, and other
                          fishes that discourage the
                          sea star predation by
                          pinching and biting their
                          tube feet
The Crown-of-Thorn Sea Star

                         The crown-of-thorns sea
                          star has undergone
                          population explosions on
                          many Pacific reefs,
                          scientists are not sure
                          what, if anything, should
                          be done about this

           Many fish,
            especially parrotfishes
            and damselfishes graze
            intensively on reefs
           If these grazers are
            removed, seaweeds can
            flourish and take over
            space from corals
           Many damselfishes act
            as “farmers,” they pull out
            unpalatable seaweeds
            and remove them, and
            what is left is a dense mat
            of tasty seaweeds
Living Together

                   Coral reefs probably have
                    more examples of
                    symbiosis than any other
                    biological community
                   Symbiotic relationships
                    are very important in
                    coral reef communities
Saving coral reefs…
 Watch the following video clips and write a paragraph in
  jour Journal on answering the following questions:
     Why are coral reefs important?
     What are reef balls?
     What are some ways of saving the coral reef?
     Do you think coral reefs should be saved?
     How can you help?
   Reef Balls
   Belize Coral Reef
   Electric Boost for Reefs
   Ocean-Saving Coral Reef
                   The End!

Thank you for your attention!

To top