Coral Biology & Ecology
Coral Questions
• What is a coral?
• What do they eat?
• How do they spread or reproduce?
• How do they get their color?
• How old are they?
• What kinds of coral do we have on the Big Island?
• What eats coral?
• What is coral disease and bleaching?
Coral Reefs Worldwide
• 284,300 square kilometers (110,000 square miles )• 0.7% of the ocean floor, support over 25% of all known marine
species
Coral Reef Facts
• Corals are over 500 million years old
• Cover over 600,000 sq kilometers of earth’s surface Estimated 88% of coral reefs are in Southeast Asia
• Since 1975, over 90% of live coral cover lost in Florida Keys
• Colonies may be 1,000 years old and attain a height of 25ft
• Atolls and barrier reefs can consist of coral limestone deposits up to 5,000 ft thick
Biogeography: Larval Dispersal
Number of species highest in “Cradle of Diversity”, with speciation declining with distance. - Viable larvae in plankton, - Rafting
Endemism
• Endemic: unique to a defined place or region and not naturally found anywhere else.
• Hawai‘i has some of the highest endemism: overall 30% of shallow water species are endemic
What is Coral?
Coral Family Tree
AnthozoaHard, soft, and precious corals, sea fans, zooanthids, anemones, sea
pens
Cubozoabox jellies
Hydrozoahydroids, medusae
Scyphozoa
true jellies
Phylum
CnidariaDefining characteristic: cnidae (nematocyst)
Polyp and Medusa stages
Polyp only
Polyp Cross Section
• Upright hollow cylinders of tissue
- Tentacles- Mouth- Stomach- Mesenterial filaments
• 2 tissue layers- Epidermis- Gastrodermis- Mesogloea (matrix
between layers
• Hard corals:- Calcium carbonate
skeleton
Coral Tissue
• 2 tissue layers
Epidermis
Gastrodermis
Nematocyst
Mucous Cells
Zooxanthellae
Stinging Cells: Cnidocytes and Nematocysts
• Cnidocytes: stinging cells on tentacles• Nematocysts: Thread with venomous
barb
The Coral/Algal Symbiosis
• Highly efficient nutrient cycling- Coral fertilizes the zooxanthellae- zooxanthellae “feeds” the coral
• Evolved to thrive in nutrient poor waters
• Very little “outside” energy needed
Symbiosis: Who benefits?
• Coral benefits:- Removes coral waste products - Provides nutrients from photosynthesis
(up to 95% of photosynthesis product)- Enhances coral’s rate of calcification
• Zooxanthellae benefits:- Gains nutrients from coral waste- Protected in tissues- Harmful UV light filtered by coral tissue
• Mutualistic symbiosis: both benefit
Hard or Stony Corals
Coral Colony: the Wall of Mouths
Coensarc
Polyp
Skeleton
Calyx
Septa
Coral Diet
• Zooxanthellae provide as much as 98% of colony’s nutrients
• Carnivorous Animals
- Zooplankton
- Tentacles and nematocysts catch prey
• Mucus Membranes
- Trap organisms, cilia pass along to mouth
- Transfer nutrients between polyps
• Absorption through cell walls
- DOM (dissolved organic matter)
Sexual Reproduction
Mature Colony
Primary Polyp
Budding & Fission
(cloning)
Settlement
BroodersInternal
fertilization
Planulae released
Sperm
Sperm
BroadcastersExternal fertilization
Synchronous releaseEgg
s
Planulae
Zygote
Asexual Reproduction
Mature Colony
Polyp Bail-out
Attachment
Budding & Fission
(cloning)
Fragmentation
Attachment
Coral Reefs of the World
Why are corals only in the tropics?
Coral Limiting Factors
Limiting factor: controls a process, such as an organism’s growth, a species population size, or distribution.
• Light Intensity
• Depth 0 – 150m
• Hard Substrate
• Low Nutrients
• Salinity: 32-35 ppt
• Sediments
Darwin’s Point
• Point where subsistence and erosion is greater than coral growth
29o N
What eats coral?
Coral Predators: Invertebrates
Coral Predators: Fish
What are coral disease and bleaching?
Coral Bleaching
• Coral Bleaching
• Response to stress - Temperature - UV - Oxygen - Darkness - Sedimentation
• Who initiates bleaching? • Can corals recover? • Where do zooxanthellae go?
• “Free” zooxanthellae are rarely found in plankton samples - May become benthic, sessile - May go into dormant stage
Coral Disease
• Montipora tissue loss
• Porites Trematodiasis
• Band Disease
• Tumors: Hyperplasia
Hawaiian Corals
Hawaiian Coral Facts
• In Hawai‘i: approximately 150 species - Approximately 45 species are reef building - Others includes
- Octocorals and soft corals- zooanthids- black and wire coral
- Hawaiian names: ‘āko‘ako‘a, ko‘a, puna kea
• The Hawaiian Islands have 410,000 acres of living reef in the main islands alone, more than the landmass of O‘ahu
Coral Growth Forms
Coral Zonation
Zonation driven by physical parameters:
• Encrusting- Very high wave energy or very
low light intensity• Branching Corals:
- Low wave energy- High light intensity- Exception: Cauliflower coral
• Massive:- Moderate wave energy- Moderate light intensity
• Columnar:- Low wave energy- Low light intensity
• Plate:- No wave energy- Very low light levels
The fight for space
• Nematocysts/Tentacles• Mesenterial filaments• Overgrowing• Shading
Branching Corals
Cauliflower Coral (Pocillopora meandrina)Most common in shallow, high
energySpawning April – May at full moon
Antler Coral (Pocillopora eydouxi)
Largest branching coralPredators: Blue-eye damselfish and butterflyfish
• Provides protection for small organisms• Reproduction: Separate sexes, broadcast spawning April–May at
full moon• Predators: Acanthaster planci, butterflyfish
Rice Corals
Blue Rice Coral (Montipora flabellata)
- Endemic- Fluorescent pigments
Rice Coral (Montipora capitata)
- encrusting, branching and plate forms
• Reproduction: Hermaphroditic, broadcast spawning April-May, full moon
• Predators: Acanthaster planci and butterflyfish
Acropora sp.
• Most common pacific coral, over 350 species
• In Hawai‘i, only 5 species in Northwest Hawaiian Islands
• Why?
Lobe Coral pōhaku puna
Green Lobe Coral (Porites lobata)EndemicMassive and encrusting growth
formsMajor reef builderReproduction: July – August
Predators: Shortbodied blenny, butterflyfish
• Massive forms, major reef builders 10 – 50 ft depth• Colonies up to 10ft high, growth 1cm/yr• Up to 400 years old
Brown Lobe Coral (Porites lutea)Polyps not fully retracted –
“fuzzy looking”Reproduction: August –
September
Predators: butterflyfish
Finger Coral
Porites compressa• Endemic• Most common species in wave-
protected areas• Complex growth form provides
protection to many organisms
• Reproduction: - Separate sexes- Syncronized broadcast
spawning, June – August full moon
• Predators: Nudibranchs and butterflyfish
Plate and Pillar Coral
• Porites rus • Common on Kona
coast• Thick columns in
shallow water and stacked plates deeper down
• Fragile plates
• Reproduction: - Broadcast spawning –
Unknown
• Predators: Butterflyfish
Mushroom Coral
Fungia scutaria • Free living polyp• Prefer calm or deep
areas
• Reproduction: - Separate sexes- Broadcast spawning- Summer, full moon- Juveniles grow on
stalk attached to parent
• Predators: Nudibranchs and butterflyfish
Other Encrusting Corals
• Corrugated Coral (Pavona varians)- Meandering ridges and valleys- Often overgrows bases of Finger coral- Separate sexes
• Crust Coral (Leptastrea purpurea)- Large calyces- Widely dispersed: High energy to deep reef- Hermaphroditic
Non-Reef Building Corals
Orange Cup Coral (Tubastraea coccinea)
Black coral (antipathes sp.) Snowflake Coral(Carijoa riisei)
Zoanthid (Zoanthus sp.)
Wire Coral (cirrhipathes sp.)
Soft corals (Sinularia sp.)
Describe this environment…
Describe this environment…
Describe this environment…