Management of Aquatic Systems

1
Management of Aquatic Systems

• River Continuum Theory Management through
  understanding of spatial changes
• Food Web Manipulations Management through
  changes in predation regimes
• Watershed and Land Use Management through
  control of urbanization

2
Food Web Manipulation

• Concept of a feeding guild
• Concept of a Trophic level
• Linear flow of energy
• Nutrients and Sunlight Driving the System
• Cycling of energy

3
TYPICAL FOOD CHAIN

• Predator-Prey Relationships
• Bottom-up control Abundance/productivity at any
  trophic level controlled by resource availability
• Top-down control abundance/productivity at any
  trophic level controlled by consumers

4
Biomanipulation

• Stocking/Manipulation of Game fish to control
  primary productivity
• Idea of trophic cascade
• Strength of links

5
Trophic Cascades

• Entire trophic levels are affected
• Removal of Top Predators
• Stocking of Top Predators

6
Importance of Top-Down vs. Bottom up Control

• Depends on number of trophic links
• Position in food chain

7
Odd-numbers of Trophic Levels
Predators

• World is green
• Predators keep herbivores in check
• Plant Biomass Accumulates
• Producers released from herbivory
• Limited by resources

Herbivores
Producers
8
Even-numbered of trophic levels

• World is brown
• Herbivores are resources limited
• Producers limited by herbivory

Top Carnivores
Carnivores
Herbivores
Producers
9
The Stability Landscape of Ecosystems

• Changes from perturbations
• Changes from steady state systems
• Resilience and Resistance

10
Exercise 1

• Seeing as how White Tail Deer are an important
  aquatic species - Are deer controlled by top down
  or bottom up forces?
• Is a trophic cascade possible?

11
Exercise 2 Next Week

• Read Paper By Power 1990.
• Do rivers/Streams Have Trophic Cascades?
• Are Streams influenced by Top Down or Bottom up
  Impacts?