Predation and Food Webs - Freshwater Ecology: Concepts and Environmental Applications - page 409

food webs from the top (predators) or the bottom (nutrients and
light). The grazer-producer link appears to be crucial in transmission
of these effects.
8. Theoretical community ecology has used aquatic food webs as systems
of study, but it is difficult to make robust generalizations about
specific food web properties that hold across all freshwater systems.
QUESTIONS FOR THOUGHT
1. If a predator is consuming prey at a rate lower than the rate at which
the prey is able to replace itself, can the effect of predation be
considered significant even if the prey population is increasing?
2. Why can increasing turbidity of large rivers cause shifts in types of
predators that are successful?
3. Why might it be more effective to control algal blooms by
biomanipulation with removal of all fish than by imposing fishing
regulations to increase the number of piscivorous fish?
4. Why are brightly colored organisms less common in freshwaters than
in benthic marine systems?
5. What single cosmopolitan species is the top predator in more
freshwater systems throughout the world than any other species?
6. Why are chemical cues to prey easier to follow in streams and benthic
habitats than in pelagic habitats?
7. How do selective pressures for streamlining of fishes conflict with
limitations on gape width?
8. Are trophic levels a valid concept in most freshwater habitats?