Reefs: Past, Present and Future. What is a Reef?

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  • Slide 1
  • Reefs: Past, Present and Future
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  • What is a Reef?
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  • There are three basic kinds of coral reefs l Fringing reefs, barrier reefs and atolls l Fringing reefs are coral reefs that grow in shallow waters and border the coast closely or are separated from it by a narrow stretch of water l Fringing reefs consist of several zones that are characterized by their depth, the structure of the reef, and its plant and animal communities
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  • Reef Zones
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  • Barrier Reefs l Barrier reefs are reefs that are separated from land by a lagoon. l These reefs grow parallel to the coast and are large and continuous. l Barrier reefs also include regions of coral formation that include the zones found in fringing reefs along with patch reefs (small reefs), back reefs (the shoreward side of the reef), as well as bank reefs (reefs that occur on deep bottom irregularities)
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  • Atolls l Atolls are annular reefs that develop at or near the surface of the sea when islands that are surrounded by reefs subside. l Atolls separate a central lagoon and are circular or sub-circular. l There are two types of atolls: deep sea atolls that rise from deep sea and those found on the continental shelf.
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  • Animals Associated with Coral Reefs l Coral reefs provide habitats for a large variety of organisms. l These organisms rely on corals as a source of food and shelter. l Some organisms that use corals through mutualism, commensalism and parasitism are within the taxonomic groups Porifera (sponges), Polychaeta (worms), Gastropoda (snails), Crustacea (shrimp & crab), Echinodermata (sea urchins) and Pisces (fish).
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  • Reefs: Past
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  • Reefs through geological time l Reefs, in some shape or form, have been around for a very long time. l Approximately 3.5 billion years ago microbialites (calcareous organo-sedimentary deposits) begin to appear in the fossil record. l These benthic microbial communities produce their own hard substrate by sequestering raw inorganic materials from the surrounding seawater. l For the next 2.5 billion years microbialites are represented by photosynthesizing cyanobacteria (blue-green algae)
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  • Stromatolites
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  • Stromatoporoids
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  • El Capitan
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  • Golden Spike Complex, Alberta l Upper Devonian l Oil discovered + 40 years ago l 4.5 billion barrels oil l 17 trillion ft 3 gas
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  • Threat to coral reefs: Hobbyists l Hobbyists seeking fish and coral for their aquariums l Aquarium owners are buying live coral at a rate that has increased 12 to 30 percent a year since 1990 l The U.N. Convention on International Trade in Endangered Species (CITES) regulates trade for 2,000 species of coral l Live fish, soft corals, anemones, crustaceans, mollusks and other creatures are not on the list Sea horse populations have dwindled by more than 25 percent since 1994
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  • 1997 I.Y.O.R. l International Year of the Reef l Reefs One of earths most diverse ecosystems Home & nursery to 0.5 million fish species Potential for biomedical resources Protection against storms
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  • Biomedical Applications l Over 6,000 unique chemical compounds l Skin-Care Products l Bone graft material l Anti-Cancer Drugs Didemnin B, diazonomide A, dolastatin 10
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  • Reefs in Crisis Pollution from poor land use, chemical loading, marine debris, and invasive alien species. Over-fishing and related harm to habitats by fishing gear and marine debris. Destructive fishing practices, such as cyanide and dynamite fishing that destroy large sections of reef and kill many species not yet harvested. Dredging and shoreline modification in connection with coastal navigation or development. Vessel groundings and anchoring that directly destroy corals and reef framework. Disease outbreaks that are increasingly prevalent in reef ecosystems. Global climate change and associated impacts such as coral bleaching, more frequent storms and rise in sea level.
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  • Land-based Pollutants l Thermal Pollution l Nutrient enrichment Sewage Agricultural runoff (fertilizers) l Pesticides, herbicides l Hydrocarbons (oil exploration, boats) l Sedimentation coastal construction deforestation soil erosion
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  • Overfishing l Overfishing of herbivorous fish interacts with the effects of eutrophication to affect the community structure of coral reefs. Jamaica is a classic example of a phase shift from a coral reef dominated community to a macroalgal community
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  • Selective overfishing l Selective overfishing of populations, for example spawning aggregations, can have particularly disastrous effects. one (1) 61cm female snapper produces the same number of eggs as two hundred and twelve (212) 41cm female snappers. 12.5kg of large snapper has the reproductive potential of 233kg of small snapper
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  • l Destructive fishing practices can destroy reef communities very effectively in a very short span of time. Dynamite fishing is an example that is also very dangerous for the human participants.
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  • Destructive Fishing l Cyanide fishing is a destructive fishing pratice common in southeast Asia. Cyanide (or bleach), when squirted into a crevice will temporarily stun fish for collection by hand. l However, the cyanide also kills coral and other invertebrates near the fish's refuge
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  • Reefs in Crisis l 10% of existing reefs destroyed l 30% threatened (destruction by 2020) l 65% depleted within 2 generations l Greatest risk areas Southeast Asia, East Africa & Caribbean
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  • Pollution, overfishing, and overuse have put many of our unique reefs at risk. Their disappearance would destroy the habitat of countless species. It would unravel the web of marine life that holds the potential for new chemicals, new medicines, unlocking new mysteries. It would have a devastating effect on the coastal communities from Cairns to Key West, Florida- communities whose livelihood depends upon the reefs. President Bill Clinton, August 1996
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  • CORAL REEFS l The rain forests of the sea, coral reefs cover more than 6,500 square miles in the Caribbean, the Gulf of Mexico, off Florida and the Pacific. They are home to an estimated 550 species of fish, and are major tourist attractions
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  • Economic Losses l The loss of these fragile ecosystems would cost billions of dollars Tourism and fishing industries u Tourism $1 billion generated annually by tourism at Australias Great Barrier Reef $1.6 billion by Floridas reefs $90 billion by Caribbean reefs and beach tourism u Fishing 6 million tons of fish also provide employment and protein for about 500 million people Damage to coastal regions that are currently protected by the coral reefs
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  • Climate Projection Models l Fate of coral reefs if increases in the emission of greenhouse gases continued Corals can live only in water between 64 degrees and 86 degrees Farenheit, coral bleaching can be triggered by a temperature increase of just 1.8 degrees above the maximum If we delay 10 years, the effect will be quite severe, and thats what this model is showing us. A delay means the death of coral reefs for probably as much as 1,000 years.(Hoegh-Guldberg, director of the Coral Reef Research Institute at Sydney University in Australia)
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  • Coral Bleaching l White spotting or dead areas l Increase in surface water temperatures stresses the coral l Expulsion of zoozanthellae
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  • Coral Bleaching
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  • Losses l A year 2000 report by the Global Coral Reef Monitoring Network concluded that 27% of the worlds coral reefs were effectively lost. l The single largest cause was the El Nino-related warming event of 1997-98, which destroyed 16% in 9 months. l The remaining 11% were lost to sediment and nutrient pollution, over- fishing and mining of sand and rock.
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  • Coral Bleaching- Consequences l Unless global warming is reversed- coral bleaching would increase in frequency and seriousness until it occurred annually everywhere as early as 2030. l A single bleaching event will take reefs between 30 to 100 years to recover l Global warming would devastate coral reefs by the middle of the 21st century and could eliminate them from most areas of the planet by 2100
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  • Future l March 2, 2000 The intergovernmental U.S. Coral Reef Task Force unveiled the first-ever national plan to comprehensively and aggressively address the most pressing challenges facing reefs today FY 2000 Federal dollars specifically targeted to cooperatively saving reefs $6 million to NOAA and $5 million to the U.S. Department of the Interior. The President requested a total of $25 million for FY 2001
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  • l National Plan Mapping $1 million per year from NOAA), NOAA estimates that all U.S. coral reefs will be mapped by 2009. Monitoring u integrated national reef moni


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