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Coral Reefs. Marine Ecology. Most diverse and productive communities DIVERSITY! Protection from wave energy Foster ecological oases Mangroves Seagrass beds Iconic ecosystem Sensitive Threatened by humans. CORAL REEFS. http://data.unep-wcmc.org/datasets. Development and Distribution.
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Coral Reefs Marine Ecology
Most diverse and productive communities DIVERSITY! Protection from wave energy Foster ecological oases Mangroves Seagrass beds Iconic ecosystem Sensitive Threatened by humans CORAL REEFS
http://data.unep-wcmc.org/datasets Development and Distribution • Biogenic • 30* N and S of equator • Cover <0.1% of global ocean surface area • Host >25% of fish species • Better than rainforests! • Species per unit area
Development and Distribution • Hermatypic • Reef-building • Tropics • Growth and distribution influenced by physical environment • Ahermatypic • Non reef-building • Mostly world-wide
Development and Distribution • Temp: 18-36*C • Types of reef based on; • Underlying substratum • Existing carbonate reef • Igneous rock • Sea level changes • Light levels • Wave action
Patch Reefs • Bommies • Small reefs • Grow in shallow lagoonal areas • Surrounded by sand • Deeper • Don’t go above surface at low tide
Fringing Reefs • Develop on shelving shores • Rocky tropical islands • Corals settle and grow on well-lighted and shallows areas • Grow toward surface
Barrier Reefs • Surround tropical islands • Separated from land by lagoon • Usually 1-10km wide • Line of breaking surf • May develop from fringing • After sea level rise • Grow quickly • Exposure to wind/currents
Atolls • A ring of reef with low-lying islands surrounding a lagoon • 10km (or more) across • Biological diversity • Seabird colonies • Charles Darwin • Formation theory http://www.youtube.com/watch?v=vrD1O5hex6Y
Reef Growth • Not continuous • Periods of rapid growth • Periods of bioerosion • Net reef growth • Fastest: 20m in 1000yrs • Usual: 3m in 1000yrs • Growth affected by sea-level • Glaciers
Corals and Coral Communities • CaCO3 skeletons • Polyps • Protection and nutrients • Zooxanthellae • Photosynthesizers • Dinoflagellate • Can live independently • No flagella/motility in polyp
Corals and Coral Communities • Zooxanthellae • Transmitted during reproduction • Obtained from seawater • Produce energy • Autotrophic • Waste from host- RECYCLE! • High rate of photosyn more calcium carbonate
http://www.youtube.com/watch?v=wsaZ8-I7akg Coral Reproduction • Recruitment • Sexual and asexual • Hermatypic • Polyps; asexual budding • Break off, settle, grow • Sexual • Long-distance dispersal • Gonochoric- one • Simultaneous- both • Sequential Hermaphrodites- change
http://www.youtube.com/watch?v=06BPlLATtgc Coral Reproduction • Brooding • Fertilized internally • Planula develops inside polyp • Broadcasting • Certain period of the year • Lunar cycle • Synchronized • Common cues • Too many eggs for the evil predators to eat
http://www.youtube.com/watch?v=_Mt0h5v4xos Coral Reproduction • Fertilized eggs • Settle in 1-3 days • Zooxanthellae aquired after settlement and metamorphosis • Brooder larvae contain them • Calcified base plate • Grazing helps growth • Influenced by environment
Coral Reproduction • LIGHTlightlightlightlight • Reef accretion • 0-10m • Hermatypic • Rare below 30m • Shallow, well-lit zone • More light • Less predators • Sunburn! • Stenothermal
Coral Growth • Evolved in stable temp • Less tolerant • Evolved in variable temp • More tolerant • Salinity 33-35ppt • Wave action currents • Nutrient spreading • Can be harmful • Hurricanes
http://www.youtube.com/watch?v=9pdmkckANH4 Coral Growth • Sediments • Some coral can remove it • Smothering, abrasion, shading, recruitment inhibition • Pulse Sediment • Storms • Not as harmful • Suspended Sediment • Human actions • Reduced light for coral
Productivity • Production recycled within the reef • Carbon fixation • Less than half the carbon they fix is available • Few organisms feed on coral directly • Reef algae • Very productive • Grazed on and carbon
Productivity • Phytoplankton! • Support zooplankton • Support larger consumers • Currents carry them across reef • Currents carry them from outlying water, and over the reef… • Then they can be eaten- YUM!!
Productivity • 24-h cycle used to measure • Day- photosynthesis • Night- respiration • Excess Production- net production which occurs (E) • Photosyn/Respiration ratio • (P/R ratio) • E=0, P/R of 1 • E is relatively low • Competition • Nutrient recycling
Reef Fauna • Could be home to over a million species • Diiiiiiiiiverse! • Not uniform • Determined by reef history and environment • Reef building coral evolved over 200 mil yrs ago • Large scale extinctions • Every 20-30 million years
Reef Fauna • Diversity • Influenced by isolation • Study • Began; 1950’s and 60’s • Focused on ecology • Realized instability • Research still young
THREATS! • Humans (of course) • We suck!! • Direct • Increased sedimentation • Fishing • Ship stupidity • Pollution • Indirection • Climate change • Over-fishin
Disease • Yes, corals get sick too • Pathogens and parasites • Can be aggravated by human influences • Black band • 1st recorded • Affects brain coral • Caused by cyanobacteria • Create anoxia in the tissue • Physically damaged • More susceptible
Bad Weather • Storms • Branching corals • Reef fish • Cyclones • (10-25* N/S) • Fast growing coral that relocate • Hurricanes • Fast growers • Acropora
Climate Change • Climate change Rising sea level • Should be good for shallow water coral • Increased ENSO due to temp increase • HUMANS • Nutrient input • Deep corals will not do well
http://www.youtube.com/watch?v=60jof35WuAo Coral Bleaching • Stressed coral expel their zooxanthellae • Skeleton becomes visible • Prolonged bleaching leads to coral death • Bioerosion takes over • Algae move in • Reduce reef accretion • Fish species will be lost • High water temperature http://www.youtube.com/watch?v=aEdoizgeNJk
http://www.youtube.com/watch?v=2fE2gIARQWA Coral Predators • Crown-of-thorns starfish • Feed on living coral • Free-spawners • 12-60mil eggs in a spawning season • Evert their stomach on coral, and secreting an enzyme which breaks down the coral • Fishing may have reduced their predators
Pollution, Sediments, Nutrients • Deforestation, port development, and dredging • Run off • Increased sediment load • Nutrients from run-off • Increased algal growth • Phosphate; big no-no • Oil pollution http://www.youtube.com/watch?v=rkKs-5JGSoo
Fishing • Expanding fisheries • Direct damage • Habitat-destructive fishing • Reef drive netting • Trapping • Blast/chemical fishing • Unselective • Illegal
Reef Growth • Limestone produced • And broken down • Coral rubble/sand • Balance between accretion and bioerosion • Erosion by organisms • Grazers • Mollusc, echinoderm, fish • Loss of hermatypic corals
Reef Animals • Difficult to record densities • Used as ‘laboratories’ • Behavior and ecology • Carrying capacity • Recruitment limitation hypothesis • Population sizes limited and determined by rates at which larval fish from plankton to adult http://www.youtube.com/watch?v=UB7tqiL-Eqs
Reef Animals • No one species can out-compete the other • Reef structure is complex • Symbiosis • Coexist • Cleaner fish • Burrowers http://www.youtube.com/watch?v=xaJdXO_j2MY http://www.youtube.com/watch?v=UJbPej8uytw
Reefs and Humans • Provide food and income • Subsistence fishing • Not recorded • Tourism • Great Barrier Reef • Over 10mil per year • Towns can be supported by revenue • Ecosystem services; help humans • Coastal defense • Coral mining, bleaching, sedimentation