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Coral Reefs

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

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  1. Coral Reefs Marine Ecology

  2. Most diverse and productive communities DIVERSITY! Protection from wave energy Foster ecological oases Mangroves Seagrass beds Iconic ecosystem Sensitive Threatened by humans CORAL REEFS

  3. 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

  4. Development and Distribution • Hermatypic • Reef-building • Tropics • Growth and distribution influenced by physical environment • Ahermatypic • Non reef-building • Mostly world-wide

  5. 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

  6. Patch Reefs • Bommies • Small reefs • Grow in shallow lagoonal areas • Surrounded by sand • Deeper • Don’t go above surface at low tide

  7. Fringing Reefs • Develop on shelving shores • Rocky tropical islands • Corals settle and grow on well-lighted and shallows areas • Grow toward surface

  8. 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

  9. 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

  10. 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

  11. Corals and Coral Communities • CaCO3 skeletons • Polyps • Protection and nutrients • Zooxanthellae • Photosynthesizers • Dinoflagellate • Can live independently • No flagella/motility in polyp

  12. 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

  13. 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

  14. 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

  15. 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

  16. Coral Reproduction • LIGHTlightlightlightlight • Reef accretion • 0-10m • Hermatypic • Rare below 30m • Shallow, well-lit zone • More light • Less predators • Sunburn! • Stenothermal

  17. 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

  18. 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

  19. 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

  20. 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!!

  21. 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

  22. 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

  23. Reef Fauna • Diversity • Influenced by isolation • Study • Began; 1950’s and 60’s • Focused on ecology • Realized instability • Research still young

  24. THREATS! • Humans (of course) • We suck!! • Direct • Increased sedimentation • Fishing • Ship stupidity • Pollution • Indirection • Climate change • Over-fishin

  25. 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

  26. Bad Weather • Storms • Branching corals • Reef fish • Cyclones • (10-25* N/S) • Fast growing coral that relocate • Hurricanes • Fast growers • Acropora

  27. 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

  28. 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

  29. 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

  30. 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

  31. Fishing • Expanding fisheries • Direct damage • Habitat-destructive fishing • Reef drive netting • Trapping • Blast/chemical fishing • Unselective • Illegal

  32. 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

  33. 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

  34. 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

  35. 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

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