Download Coral Reefs

Coral Reefs
Georgia’s Gray’s Reef
Gray's Reef is not a coral
reef. It is not built by living
hard corals as tropical reefs
are. Instead it is a
consolidation of marine and
terrestrial sediments (sand,
shell and mud) which was
laid down as loose aggregate
between six and two million
years ago. At one time,
Gray's Reef was dry land!
Coral reefs cover less than
0.2% of the ocean surface
yet they are home for ¼ of
all marine fish species!
Sponges, nudibranchs, fish (like Blacktip Reef Sharks, groupers,
clown fish, eels, parrotfish, snapper, and scorpion fish), jellyfish,
anemones, sea stars (including the destructive Crown of Thorns),
crustaceans (like crabs, shrimp, and lobsters), turtles, sea snakes,
snails, and mollusks (like octopuses, nautilus, and clams). Birds also
feast on coral reef animals
Types of Coral
Two types:
• Stony (hard) coral
• Soft coral
Stony Corals
• Made up of limestone (calcium carbonate)
• Hard, rocklike
• Brain coral, staghorn coral, star coral
Soft Coral
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Made of fibrous protein
Flexible
Looks like a plant swaying in current
Ex. sea fan, sea whip, and sea plume
Coral Animal
• Polyp (Cnidaria)
• Mouth, tentacles,
digestive cavity,
attached to substrate
• Colonial animals
• Corals are carnivores
that eat zooplankton
coral spawning
• Attached to one
Can reproduce
another by thin
membrane connecting asexually (budding)
digestive system
and sexually
(spawning)
• Coral Reef Spawning – YouTube
brain coral releasing eggs
Mutualism (Symbiosis)
Zooxanthellae –
provides oxygen
and food to coral
Coral – provides
safety and
nutrients to algae
Zooxanthellae
Coral Reef Formation
• Built by corals
• Specialized cells take calcium from the
seawater
• Zooxanthellae (dinoflagellate algae)
captured by polyps, collect CO2
produced by polyps
• Combine to make calcium carbonate
(CaCO3)
• Polyp secretes CaCO3 to make new
layers of coral reef
Coral Reef Location
• Tropical areas, shallow waters
• Warm waters to secrete CaCO3
skeletons
• Clear water, free from sediment –
need sun to photosynthesize
location of major coral reefs in red
Coral Growth
• Each generation lays down a layer of
reef
• Massive corals slow growing - a rate
of 0.5 to 1 cm/year
• Branching corals grow faster – a rate
of 10-20 cm/year
• Provides homes and habitats for
other species
• Large reefs protect nearby coast
lines from ocean waves/storms
branching
pillar
table
elkhorn
foliase
encrusting
massive
mushroom
Damage to Reefs
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Ship damage
Ecotourism
Water pollutants
Severe storms
Freshwater runoff
Sediment
High or low water temperature (disturbs algae)
• Coral bleaching
– Living polyp dies off
– White skeleton remains
Additional Damage
• Fishing has degraded reef communities by upsetting the
ecological balance
• Dynamiting (Indonesia, Kenya) has killed hard coral colonies
• Muro-ami = bouncing rocks tethered to lines off the coral to
herd fish has caused serious damage
• Formation of coral islands - YouTube
Types of Reefs
• Fringing reefs
• Barrier reefs
• Atolls
Fringing Reefs
• Connects to shore on leeward side
(the direction downwind) of land
• Water shallow on shore side
• Water deep on ocean side
• Grows most rapidly on ocean side due
to greater water circulation (more
food and oxygen to coral)
• Florida Keys, Caribbean
Barrier Reefs
• Approximately 25 km off shore
• Separated from island by a
channel/lagoon
• Great Barrier Reef
– Series of reefs, largest structure made
by living organisms
– 10 to 160 km off northeast coast of
Australia
– 350,000 km2
Fringing & Barrier Reefs
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Grow right up to ocean surface
May be exposed at low tide
Waves and currents break off pieces
Accumulate on seafloor
Coral pieces pile up to form small
islands called keys or cays
• Florida Keys and Cayman Islands
Atolls
• String of coral islands forming a
circle around a shallow lagoon (1 to 12
km wide)
• Darwin hypothesized about cause of
atoll shape – the final stage in reef
evolution
• Mostly in Pacific
Formation (Darwin’s Theory)
1.
Fringing reef appears along shoreline of
volcanic island
2. Island begins to sink or erode and reef
continues to grow up and out to for
barrier reef
3. Island sinks completely below surface
leaving an atoll
• Scientists confirmed Darwin’s theory by
drilling through limestone and finding a
volcanic foundation beneath the reef