Coral Reefs

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• Coral Reefs
• -Are produced by the organisms that live on them
• Are produced by a soft bodied polyp similar to
  and related to an anemone
• Very diverse ecosystem
• Coral Anatomy Growth
• Reef forming corals secrete CaCO3
• Are members of the Phylum Coelenterata, Class
  Anthozoa
• Are radially symmetrical
• Subclasses
• Soft Corals- sea fans, sea pens, sea whips
• Hard Corals- stony corals (make the reefs)
• Are carnivores, tentacles have nematocysts to
  capture prey and bring it into the digestive
  cavity

• -Most corals live in colonies
• Each polyp sits in a hard limestone cup called a
  corallite
• Which is made by their epidermis
• The polyp grows by drawing itself up a secreting
  a new layer in the bottom of the cup
• All the polyps are connected over the top of the
  calcium cup by a thin tissue layer called a
  cenosarc, so touching and tearing this tissue can
  injure the coral and let infections in.

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Corals have a symbiotic relationship with a
unicellular algae, zooxanthellae Corals give off
carbon dioxide which is taken in by the algae and
is converted to sugar and oxygen is given off.

Stony corals are found in many varieties. The
rate of growth will depend on the type of coral.
Branching corals grow faster than massive corals
(brain). Corals will show growth in the rate of
growth is more than the rate at which they are
broken down.
PHOTOSYNTHESIS In zooxanthellae
CO2
O2
H2O
Sugar
RESPIRATION in coral polyp
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The growth rate of coral reefs is affected
by Light intensity Water motion Water
depth Turbidity Sedimentation Length of day Water
temperature Plankton concentration Predators
(sea urchins, parrot fish, some algae)

• Coral Distribution
• -non-reef forming corals are found in deep oceans
  and in temperate zones
• -reef forming corals are found in tropical and
  subtropical waters
• -reef forming corals are usually found on the
  eastern side of continents more so than on the
  west
• -reef forming coral are found in normal salinity
  seawater exception is near the Amazon River
  where a large amount of freshwater flows into the
  Atlantic
• reef forming coral are found within 25-70 m of
  the surface of the water
• corals need warm water to deposit the calcium
  carbonate easily

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Coral Reef Formation Two general types of
reefs 1.Shelf Reefs- form off the continental
margin (shelf) also a fringing reef- a coral
reef that closely borders the shoreline 2.
Oceanic Reefs- form around islands - three
types of oceanic reefs a. fringing reef- ex.
thru/out the Red Sea b. barrier reef- are
further offshore and are separated from the
shoreline by a lagoon Ex. Great Barrier
Reef- Australia c. atoll- a ring shaped chain
of coral reefs from which a few low islands
may project above the surface of the
water ex. Marshall Islands
http//www.oceanservice.noaa.gov/education/corals/
media/supp_coral04a.html
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It has be theorized that each of the types of
reefs are actually an evolutionary process. Newly
formed volcanic islands become populated with
coral polyps? which as they grow from a fringing
reef along the shoreline? waves cause pieces of
the reef to break loose and move down the sides
of the volcano? where more corals now develop
upward toward the waters surface? the weight of
the growing coral reef and the cooling of the
volcano causes the island to sink ? creating a
barrier reef ? further sinking of the island
below the waters surface which leaves a lagoon
ringed by a group of islands that are supported
by coral reefs called atolls
See pg 273 Figure 10.7 of text
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Reef Zones
Algal ridge- a low jagged coral ridge on the
windward side of the reef- affected by wave action
Buttress- seaward side of a reef, no deeper than
20 m- affected by continuous heavy wave action
Reef Flat- the portion of the reef that extends
behind the algal ridge to the island- nearly
flat, level surface barely covered by water
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Coral Reproduction
Corals can reproduce asexually or
sexually Asexual reproduction can be from a.
budding where a smaller version of the adult
breaks off from the polyp b. fragmentation
where a section of coral reef breaks off
from the rest of the colony - could be
beneficial if the type of coral has a fast
growth rate - one type of coral could
dominate a reef - reduces the chances of
altering the species as with sexual
reproduction (the gene make-up of an
organism) Sexual reproduction- eggs can be
fertilized internally where they are held in
the digestive cavity until motile sperm cells
fertilize the eggs and they can stay there and
develop before being released into the water
can be released right away or fertilized
externally where the eggs sperm are released in
the water to fertilize and develop in the open
ocean
Corals spawn synchronously (at the same time)
right after a full moon, but it is not true for
all corals in all areas. This could cause
problems if a rainstorm and drop in salinity
occurs at the same time. It could wipe out a
whole reproductive season in that species of
coral.
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Coral Reef Fish
Fish use the reefs for protection, prey on
plants, algae, and animals living there. Some
will even eat the reef. Fish are an important
part of the reef community because they bring in
nutrients from other areas through waste material.

• Symbiotic Relationships on the Coral Reef
• Mutualism- remoras and sharks also called
  inquilinism which is a benefit of protection from
  the relationship.
• Cleaning Symbiosis is a form of mutualism
• Commensalism- shrimpfish face down among the
  spines of a sea urchin, where the shrimpfish
  benefits but the urchin doesnt.
• Parasitism

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Purposes of different color patterns
Animals that rapidly change their skin coloration
to match their environment do so by expanding and
contracting pigmented cells in their skin called
chromatophores. Iridocytes are cells that contain
reflecting crystals which can produce a wide
variety of colors.
Concealment
Disruptive coloration, contrasting lines, false
eye spots are all used to distract and disguise
predators.
Disguise
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Bright colors can be used to attract potential
mates or warn others that a fish of animal may be
poisonous.
Mimicry to look like a friendly fish or one that
may be dangerous
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Mimicry to look like a friendly fish or one that
may be dangerous
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Coral Reef diversity rivals that of tropical
rainforests. This many be in part to constant
attack from natural agents ie. storm waves
therefore, there is a constant changing of the
ecosystem with a constant changing of primary
species
Coral Reef Mortality
1. Predators to Coral Reefs Parrot fish 2. Crown
of Thorn Sea Stars- if allowed to overpopulate
because their natural predator (a snail) is
removed will damage reefs or large amounts of
larva are swept in to the region 3. Sea Urchins
that graze on algae are suddenly killed and then
the algae is allowed to overgrow, it competes
for space on the reef. 4. Blackband Disease- a
cyanobacterium that grows ina dense matt and
separates the cenosarc from the skeleton
allowing other pathogens to come in a kill the
coral polyp. It appears as a black band of dead
tissue as it moves over the reef. 5. Bleaching-
stressed corals get rid of their zooxanthellae
causing the coral to turn white. It can be
caused by temperature changes, excess ultraviolet
radiation may cause this. 6. Sedimentation 7.
Nutrification- excess nutrients in the water will
enhance algae growth, this can occur when
fertilizers run off into the rivers and reach the
nearby coral reefs
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Blackband Disease
Yellowband Disease