Understanding Energy and Materials Flow in Ecosystems

1. Lecture 11 Introduction to Environmental Engineering Ecosystems

2. Energy and Materials Flow in Ecosystems • Energy and Materials both flow in Ecosystems • Energy only up the trophic levels • Materials flow is cyclical • Energy • Photosynthesis Producers (plants) • Respiration  Consumers (animals) • Decomposers • Energy conversion is highly inefficient

3. Energy and Materials Flow in Ecosystems • Producers take energy from the sun [nutrients] +CO2 + sunlight  O2 + [high energy molecules] • Consumers respire [high-energy molecules] + O2CO2 + [nutrients] Waste formed known as detritus Decomposers break-down detritus from plants and animals

4. Energy and Materials Flow in Ecosystems • Energy flow is one way Sun  plants  animals  decomposers

5. Energy and Materials Flow in Ecosystems • Materials Flow is cyclical • After all, mass can neither be created or destroyed

6. Energy and Materials Flow in Ecosystems

7. Energy and Materials Flow in Ecosystems • Microbial Decomposers • Aerobic degradation [detritus] + O2 CO2 + H2O +[nutrients] • Anaerobic degradation [detritus]  CO2 + CH4 +H2S +NH3 + … + [nutrients] Both anaerobic and aerobic bacteria are used in wastewater Microbes are obigate aerobes, facultative, or obligate anaerobes.

8. Energy and Materials Flow in Ecosystems • Mass Balances can be performed on ecosystems • When at steady-state an ecosystem is said to be in homeostasis • The food web/food chain is in balance • Organisms at various trophic levels are in balance

9. Energy and Materials Flow in Ecosystems • If a species can grow with no constraints • No predators, lack of food, lack of space (humans) • Growth is: Where N = # of organisms k = constant t = time

10. Energy and Materials Flow in Ecosystems • However growth inhibitors do exist

11. Human Influence on Ecosystems • Effect of Pesticides • Effect of Nutrients on Lakes • Effect of Organic Wastes on Streams