34_Energy_and_Nutrients - Ecosystem Ecology I Energy and...

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Unformatted text preview: Ecosystem Ecology I: Energy and Nutrients Ecosystem Ecology I: Energy and Nutrients Today's questions: I. How does energy move through ecosystems? II. How do nutrients move through ecosystems? I. How does energy flow through ecosystems? A. Patterns in net primary productivity I 1. Where is NPP/km2 particularly high? 2. Why is NPP/km in the open ocean so low, if lots of 2 Wh is NPP/km2 in the open ocean so lo if lots of light is available and the water is warm? 3. Why does so much of the total NPP come from the open ocean? Patterns in net primary productivity II 4. Are the data on the map consistent with the data in the bar charts? Explain any discrepancies. 5. What limits productivity in terrestrial habitats? 5. What limits productivity in terrestrial habitats? 6. In the open ocean, what happens to nutrients available p pp in organisms living at the surface? 7. In the open ocean, why aren't nutrients recycled from the benthos? B. What happens to NPP? 1,254,000 kcal/m /yr in sunlight 1 254 000 kcal/m2/yr in sunlight kcal/m2/yr captured by photosynthesis (0.8%) kcal/m /yr k l/ 2/ kcal/m /yr to k l/ 2/ t to growth (45%) respiration/maintenance (55%) kcal/m2/yr kcal/m2/yr to consumers to decomposers What percentage of NPP gets eaten as living tissue? C. Trophic levels in a food chain or food web p Trophic level Feeding strategy Grazing food chain Feeding strategy Grazing food chain 5 40 consumer 4 30 consumer 4 3 3 20 consumer 2 10 consumer Copepods, other small animals 1 Autotroph Photosynthetic algae & bacteria D. Efficiency of energy transfer at Hubbard Brook y gy grams of tertiary consumer ( % efficiency) grams of secondary consumer ( % efficiency) grams of primary consumer ( % efficiency) Start: 1000 grams of primary producer ~1% of incident sunlight to primary production 8. Why is so much energy lost at each transfer? y gy 9. Which is more efficient as a primary consumer, a fish or a cow? Why? 10. Clams and mussels eat detritus as well as small primary producers and consumers. Would you consider them an efficient consumer? II. How do nutrients flow through ecosystems? Nitrogen cycle, water cycle, carbon cycle, etc: atoms move through ecosystems, from organism to organism g y g g in food webs and to/from the abiotic environment (water, soil, atmosphere) Humans are altering most biogeochemical cycles in massive ways massive ways e.g. altering the nitrogen cycle g g g y Why is nitrate pollution occurring in Hood Canal? 1. Ammonia/Urea/NH2containing molecules are released from septic systems 2. Bacteria and archaea in the soil oxidize these compounds to nitrate (water soluble) What are some possible solutions? ...
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