Ecology of Rivers & Coasts: Food Webs & Human Impacts

Lecture 1 – Trophic Cascades in Rivers

by Mary E. Power, PhD

  1.  1.  Introduction and start of Lecture One
  2.  2.  Food webs depict energy and nutrient flow through trophic levels
  3.  3.  Trophic cascades are an example of top-down control
  4.  4.  The number of trophic levels may determine limitations on plant growth
  5.  5.  Problems with food chain theory
  6.  6.  River ecosystems offer opportunities to study species interactions
  7.  7.  Traits of grazers impact food webs in different ways
  8.  8.  Armored catfish are model organisms for studying productivity in streams
  9.  9.  Methods of observing catfish and measuring grazing impact
  10. 10.  Catfish grow at the same rate in sunny and dark pools
  11. 11.  Armored catfish are ideal free grazers
  12. 12.  Armored catfish avoid shallow parts of river to escape predation
  13. 13.  Number of trophic levels determines if ecosystem is green or barren
  14. 14.  In Brier Creek, green pools have large-mouthed bass and no minnows
  15. 15.  Floods rearrange fish distribution
  16. 16.  Minnow addition experiment; impact on algae biomass
  17. 17.  Bass addition experiment: turn a barren world into a green world
  18. 18.  Traits of grazers affect food chain length and trophic cascades
  19. 19.  Biomass pyramid can be inverted because of algal productivity
  20. 20.  Ecosystem services depend on the length of the food chain
  21. 21.  Q&A: What do bass eat when there are no minnows?
  22. 22.  Q&A: What can we do to sustain water ecosystems for human use?
  23. 23.  Q&A: How many minnows do bass eat?
  24. 24.  Q&A: Did the bass-minnow replicate what would happen naturally?
  25. 25.  Q&A: Can you add species to control nitrates in freshwater ecosystems?
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