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Do ecosystems need predators?

Do ecosystems need predators?. What role do sharks and other top predators play in the coral reef ecosystem?. Some review of basic ecology ideas may help you answer the last question .

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Do ecosystems need predators?

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  1. Do ecosystems need predators?

  2. What role do sharks and other top predators play in the coral reef ecosystem?

  3. Some review of basic ecology ideas may help you answer the last question  An ecosystem is defined as a community of living things that interact with each other and their environment

  4. Food webs describe the pathway for energy or elemental flow Although a bit simplified, the basic energy flow pattern starts with the sun. How does energy travel through coral reef systems? Toproducers(algae and bacteria) Then toconsumers(animals that eat producers)

  5. It’s more complex than that…. • Producers capture about 10% of the sun’s energy through photosynthesis • Primary consumers range from tiny zooplankton to herbivores • Secondary consumers are those that eat primary consumers • Top consumers consist of apex predators

  6. Then there’s entropy • Each level of transfer in a food web is called a trophic level (trophic-trophikos: Greek word for nourishment) • Only about10%of energy is transferred to the “next” level! 90% is lost to heat, respiration, etc. • Because of inefficient energy transfers higher trophic levels require more energy than lower trophic levels to produce the same amount of biomass • Allmassis transferred (mass is not destroyed) but is not necessarily used

  7. Food webs also (re)cycle vital chemicals Atmosphere Algae Phosphorus Fish Zooplankton Nitrogen Carbon Invertebrates Bacteria

  8. Scientists are still trying to answer many questions aboutmarine food webs! Scientists are just beginning to better understand the role that microorganisms play

  9. There is also much to learn about the interaction of terrestrial (land) and marine ecosystems

  10. Can you add to or revise the first two answers on this worksheet? Please try to do so now  Do ecosystems need predators? What role do sharks and other top predators play in the coral reef ecosystem?

  11. Scientists studying the biomass of fish species in various trophic levels in the Hawaiian Islands have collected some surprising data! Examining some of these findings may also assist you in determining the answers to the questions you just considered

  12. What can you conclude after analyzing this data? Look closely at the Main Hawaiian Islands vs. those of the Papahānaumokuākea Marine National Monument You may want to look at the map on the next slide and then return to this slide 

  13. Papahānaumokuākea Marine National Monument Main Hawaiian Islands

  14. Graphing data is a helpful analysis tool

  15. Graphic displays are another way to represent and analyze data Scientists are also using geographic images and global positioning data more frequently

  16. Geographic pattern of apex predator biomass density (t ha-1) at the 10 emergent Northwestern Hawaiian Island (NWHI) reefs surveyed during September/October 2000, 2001 and 2002 (DeMartini and Friedlander 2004)

  17. The data collected to date supports a surprising conclusion!

  18. The protected reef ecosystems of the Papahānaumokuākea Marine National Monument are dominated by apex predators!

  19. Compare the fish biomass of Papahānaumokuākea Marine National Monument to the Main Hawaiian Islands! Apex Predators 54% Apex Predators 3% Other Secondary Consumers 18% Other Secondary Consumers 42% Herbivores 28% Herbivores 55%

  20. On some islands within the monument, predators account for double the biomass of fish in the other trophic levels! French Frigate Shoals Biomass Data (metric tons per hectare) Apex Predators: 1.7 Other Secondary Consumers: 0.3 Herbivores: 0.6 Apex Predators Other Secondary Consumers Herbivores

  21. The reef ecosystems of the monument are thriving, containing more numbers and greater size of fish than those of the Main Hawaiian Islands Gardner Pinnacles – James Watt

  22. The islands in the monument also have flourishing coral, algae and invertebrate colonies too! French Frigate Shoals – James Watt

  23. There is a marked difference between the reefs in the monument and those of the Main Hawaiian Islands! Maui - NOAA

  24. Reefs in the Main Hawaiian Islands are dominated by smaller herbivorous fish Hanauma Bay, Oahu – Donald Miralle

  25. Can you explain why apex-dominated reef ecosystems have:1) more fish2) larger fish and3) healthier corals and benthic communitiesthan those with fewer and smaller predators? Try!

  26. Acknowledgements • Zachary Johnson, SOEST, University of Hawaii Manoa • George Wright, Montana State University • James Watt • Alan Friedlander, Ph.D

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