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Human Impacts on Coral Reefs
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  1. Human Impacts on Coral Reefs Natural Stresses and Human Uses

  2. What is Coral Reef? • Symbiosis between polyp and photosynthetic algae • Excrete calcium carbonate (limestone) as polyp’s shell

  3. Global Distribution of Reefs

  4. Factors Correlated with Healthy Coral Reef Growth • water temperature range: 18 – 29C • normal seawater salinity: 32 – 35 ‰ • low inorganic nutrient concentrations (oligotrophic waters) • clear, transparent water • little or no sedimentation • vigorous water motion

  5. Thursday, October 26, 2006Massive loss of coral reefs is predictedBy Matt Probasco THE ASSOCIATED PRESSCHARLOTTE AMALIE, U.S. Virgin Islands — Researchers fear more than half the world’s coral reefs could die in less than 25 years and say global warming may be at least partly to blame. Last year’s coral loss in the Caribbean waters supports predictions that 60 percent of the world’s coral could die within a quarter century, said Tyler Smith of the University of the Virgin Islands.Up to 30 percent of the world’s coral reefs have died in the last 50 years, and another 30 percent are severely damaged, said Smith, who studies coral health in the U.S. Virgin Islands and collaborates with researchers globally. Human Impacts on Coral Reefs Report: Caribbean coral reefs down 80 percent By Marsha WaltonCNNThursday, July 17, 2003 (CNN) --A new study paints a grim picture of the health of coral reefs across the Caribbean. In the past three decades, the amount of coral cover has dropped about 80 percent, according to researchers in the journal Science.

  6. 20% of coral reefs were lost and an additional 20% were degraded in just the last several decades of the twentieth century. Source: United Nations Environment Programme (UNEP). 2005. Millennium Ecosystem Assessment

  7. Natural Sources of Stress on Coral Reefs • intense storms • El Niño • disease • volcanic eruptions • predator population explosions • natural stream and river runoff • exceptionally low tides

  8. Storm Wave Damage Before After

  9. Storm Damage

  10. Disease

  11. Stream and River Runoff

  12. Human Impacts on Coral Reefs

  13. Some Local Human Impacts • thermal effluents • sewage discharges and agricultural runoff • mechanical damage to reefs • sedimentation • destructive resource extraction practices • introduced species • loving a reef to death

  14. Global Human Impacts • global warming • excessive carbon dioxide in atmosphere • ozone depletion

  15. Possible Consequences of Stresses and Impacts on Corals and Coral Reefs • outright mortality of coral tissues • breakage of coral colonies • bleaching • diseases • slower growth • competitive exclusion by other organisms • increased reef erosion

  16. Coastal Development

  17. Modern Uses of Coral Reefs • Seafood • Food Additives and Toiletries • Health and Medicine Products • Research and Education • Jewelry and Art • Marine Aquarium Specimens • New Land • Cement & Other Building Supplies • Shoreline Protection • Recreation

  18. Coral Bleaching

  19. Global Bleaching

  20. Some causes of coral bleaching • Unusually high or low temperatures • Unusually high or low salinity • High amounts of visible or ultraviolet light • Sedimentation • High levels of nutrients (sewage, etc.) • High levels of toxins (pesticides, etc.)

  21. Sea Level Rise

  22. Sewage Discharge and Agricultural Runoff

  23. Sewage Discharge and Agricultural Runoff • ecological consequences • phytoplankton bloom reduces light penetration and promotes growth of filter-feeding bioeroders • benthic seaweeds overgrow and smother corals

  24. Nutrients and Algae Growth

  25. Toxic Chemical Spills

  26. Other Wastes

  27. Dredging

  28. Mining of Reef Limestone

  29. Anchor Damage

  30. Diver Damage

  31. Net Damage

  32. Atomic Testing

  33. Sediment Runoff

  34. Sediment Plume Entering the Ocean

  35. Corals Smothered in Sediment

  36. Destructive Resource Extraction Practices • overfishing • use of dynamite to catch fish • use of bleach or cyanide to catch fish • breakage of coral to remove fan worms • collection of live coral or rocks

  37. Dynamiting Reef

  38. Introduced Species Acanthophora, Eucheuma, & Gracillaria

  39. Loving a Reef to Death • walking on reefs • diver damage • fish feeding • excessive recreational use

  40. Feeding Fish

  41. Hanauma Bay

  42. Non-Point Source Pollution

  43. Types of Non-Point Source Pollution • sediments from coastal urban and agricultural development • nutrients from detergents, fertilizers, leaky septic tanks, and domesticated animals • pesticides (home use, agricultural, & golf courses)

  44. Types of Non-Point Source Pollution • automobile wastes such as combusted motor oil, tire rubber, brake pad dust, coolant, etc. • waste water from swimming pools and aquaculture ponds