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 DispersalNumber 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 Phylum Cnidaria Defining characteristic: cnidae (nematocyst) Polyp and Medusa stages Polyp only Scyphozoa Anthozoa Hydrozoa true jellies Hard, soft, and precious corals, sea fans, hydroids, medusae zooanthids, anemones, sea pens Cubozoa box jellies
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 Polyp Calyx Coensarc Skeleton 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)
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 growth29o 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
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 ZonationZonation 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• Provides protection for small organisms• Reproduction: Separate sexes, broadcast spawning April–May at full moon• Predators: Acanthaster planci, butterflyfish Antler Coral (Pocillopora eydouxi) Cauliflower Coral (Pocillopora Largest branching coral meandrina) Predators: Blue-eye damselfish and Most common in shallow, high energy butterflyfish Spawning April – May at full moon
Rice Corals• Reproduction: Hermaphroditic, broadcast spawning April-May, full moon• Predators: Acanthaster planci and butterflyfish Blue Rice CoralRice Coral (Montipora flabellata)(Montipora capitata) - Endemic - encrusting, branching and - Fluorescent pigments plate forms
Acropora sp.• Most common pacific coral, over 350 species• In Hawai„i, only 5 species in Northwest Hawaiian Islands• Why?
Lobe Coral pōhaku puna • Massive forms, major reef builders 10 – 50 ft depth • Colonies up to 10ft high, growth 1cm/yr • Up to 400 years oldGreen Lobe Coral (Porites lobata) Brown Lobe Coral (Porites lutea) Endemic Polyps not fully retracted – “fuzzy Massive and encrusting growth forms looking” Major reef builder Reproduction: August – September Reproduction: July – August Predators: butterflyfish Predators: Shortbodied blenny, 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 Black coral (antipathes sp.) Snowflake Coral (Carijoa riisei) Wire Coral (cirrhipathes sp.) Soft corals (Sinularia sp.) Orange Cup Coral (Tubastraea coccinea)Zoanthid (Zoanthus sp.)