Download What is a coral? - Florida Department of Environmental Protection

What is a coral?
• Is it an animal? Is it a plant? Is it
something else entirely?
Corals – A Symbiotic Organism
• Corals belong to Phylum Cnidaria
– Closely related to jellyfish and sea anemone’s
• Zooxanthellae are protists known as
dinoflagellates
– Unicellular and Photosynthetic
– Closely related to organisms involved in red
tides
Corals – A Symbiotic Organism
• A case of Mutualism
– Both organisms benefit from the close
relationship
• Corals provide zooxanthellae with lodging
and a window
• Zooxanthellae provide coral with some
food from photosynthesis
Coral Anatomy
• Living portion of coral is only a thin
superficial layer
– Subsurface is a calcareous skeleton
Coral Bleaching
• Whitening of corals due to loss of their
zooxanthellae
– Various environmental variables may cause
this to occur
• Temperature – Prolonged increase (32 C)
• UV exposure
• Lower light levels ~ increased turbidity
• Pollution
• Disease
Coral Bleaching
Coral Feeding
• Suspension Feeders
– Tentacles capture planktonic prey
– Nematocysts adhere to prey and paralyze
them
Coral Feeding
• Most are Nocturnally
Active
– More zooplankton at
this time
– Reduce predation on
tentacles
– Reduce UV exposure
– Reduce self shading
Coral Asexual
Reproduction
• Corals are made up of colonies of polyps
• Coral colonies expand and grow via
budding
• One polyp splits and forms two
Coral Sexual Reproduction
• Mass spawning events
– Few days after new
moon
• Gametes released
simultaneously
– Float to surface and
fertilize
• Why and how?
Coral Reefs
• Definition:
an underwater formation built out of
calcium carbonate by marine animals and
plants, and which is strong enough to
stand up to the force of ocean waves.
Coral Reefs
• Reef building corals typically occur
between Tropic of Cancer and Capricorn
Most from 23 ½° N & S, Some 30 N & S
Coral Reefs
• Requirements
1. Light – typically found in shallow water (090’ ) = fastest growth
Can grow at depths up to 60 m (within
photic zone)
2. High Visibility
minimum of 10 m
typically 20-30 m
Coral Reefs
• Requirements
3. Temperature – ideal between 23-25°C
(73-77°F); can grow between 16-36°C (6197°F)
4. Salinity – 25-40 ppt
- typically not near river
deltas (fw, nutrients, vis.)
Deepwater Corals
• Oculina Bank >80 m
-nonreef building
-slow growth
-no zooxanthellae
-rely on plankton
-Impt Habitat for
deepwater fishes
Coral Reef Types
• 3 Major types – Darwin 1842
1. Fringing – close to shore, may be attached
to land mass
- influenced by runoff, most common in Caribbean
Tortola, BVI
• Where’s the fringing reef?
– Muddy waters smother reefs
• Rapid urbanization = high runoff
Coral Reef Types
• 3 Major types – Darwin 1842
2. Barrier – develop far from shore and have
extensive deep lagoon
- GBR and Belize
Coral Reef Types
• 3 Major types – Darwin 1842
3. Atoll – circular or
horseshoe shaped
- Surround islands
- Start as fringing reef
Coral Reef Types
4. Other reef types
a) Patch reefs
- isolated boulders of coral
- typically found in lagoons and on the leeward side
of barrier, fringing and bank reefs
- surrounded by seagrasses and sand flats
Keys Patch Reef Clip
Feeding Halos caused by inverts and fish
Coral Reef Types
Coral Reef Types
4. Other reef types
b) Bank reefs – found seaward of patch reefs, deep
waters >20 m nearby
- form an elongate, broken arc from Miami south
along the Florida Keys to the Dry Tortugas.
- may contain a shallow lagoon ~ 20’ in keys
Florida Bank Reef
Reef Zonation
Reef Zonation: Backreef
Patch Reef
the backreef zone
Low energy zone, high variability in temp and salinity,
high sedimentation rates
Reef Zonation: Reefcrest
High Energy (Breaking waves)
Low tide exposure
Coralline algae and hardy
corals dominate
Reef Crest
Reef Zonation: Forereef
Forereef
Optimal Habitat for Coral Growth
Usually contains a spur and groove zone
Reef Zonation: Forereef
Spur & Groove / Buttress Zone
Florida Keys Reefs
Geologic History of Reefs
• True coral reefs first appeared in late
Cretaceous ~65 mya
• Reef fishes (Perciformes) also first
appeared during this time
• Majority of modern day reef fishes date
back to Eocene (54-30 mya)
Present Reefs are Young!
• The Great Barrier Reef is only ~10,000 yrs
old
– no reefs in this area for 100,000 prior
• The Keys Islands (Key Largo, Islamorada,
etc.) were all coral reefs between 95-320k
years ago
– Most of Florida was submerged
– Sea level was 6-8 m higher
Present Florida Reefs
• Younger than GBR
– Deeper reefs are older
• Formed 5-7k years ago
– during glaciation event = lower sea levels
• Currently sea leveling rising, glaciers
melting = many reefs drowning
Coral Reefs and Sea Level
Broward’s Reefs
5k
7k
Why are coral reefs important?
• “Rainforests of the Sea”
– One of the most diverse and productive
communities on earth
– Reef organisms possess antimicrobial and antiviral
compounds
• AZT, an HIV treatment (Caribbean reef sponge)
• Prialt, a painkiller (cone snail venom)
• Red Algae compounds - new cancer drug (apoptosis)
Why are coral reefs important?
• Shore protection
– Storm wave energy absorbed and blocked by reefs
• Land builders (tropics)
– Islands formed from relic reefs
– South Florida is primarily built upon an ancient
coral reef
• Economic Boost
South Florida (Monroe, Dade, Broward, Palm Beach)
– $7.6 billion annual revenue
– More than 70,000 jobs
Why are coral reefs important?
THE MOST IMPORTANT FUNCTION OF A
CORAL REEF =
• Provides shelter for the FISH!!!
– Oh yeah, inverts too ☺
• Occupy 0.2% of World’s Oceans and
support 1/3 of all fish species
Coral Reef Fishes
Widespread, circumtropical, small, sessile
Diversity – 4000 spp. on indo-pacific reefs
450-500 spp. in Caribbean
Provide food and protection for
corals