1. Environmental Systems
Chapter 5
Environmental Systems

2. Chesapeake Bay
Chesapeake Bay used to be the world’s largest oyster fishery
By 2010, output reduced to 1% of historical levels
Numerous causes of the decline:
Overharvesting
Habitat destruction
Disease
More recently, nutrient addition (nitrogen and phosphorus) from fertilizer, fossil fuel emissions, storm water runoff
Hypoxia = low concentrations of oxygen in water

3. Key concepts
Hypoxia- When phytoplankton die, settle to the bottom and are decomposed by bacteria, oxygen in the water is depleted. Creates dead zones. (Oxygen sag curve)
Dissolved Oxygen
(oxygen sag curve)

4. Eutrophication https://www.youtube.com/watch?v=UGq ZsSuG7ao
Fertilizers
Leaching into water
Water plants grow
No sunlight
Algae die, plants die
Bacteria decompose dead plants
Bacteria takes all the oxygen up!
Fish die!

5. Earth is a system!
System = a network of relationships among parts, elements, or components
They interact with and influence one another
They exchange energy, matter, or information
Systems receive inputs of energy, matter, or information
They process these inputs and produce outputs
Feedback loop = a circular process in which a system’s output serves as input to that same system
Negative and positive feedback loops do not mean bad and good

6. Positive Feedback Loop
Amplifies change in system by causing further increase or decrease
Example: In increase causes more of an increase and a decrease causes more of a decrease.
Example: More births equal a larger population which will have more births.

7. Negative Feedback
This feedback occurs when a system resists change by returning to original state or slowing rate of change.
Example: In a lake when the water level drops, the surface area for evaporation drops. Evaporation above the lake is reduced causing the water level to rise.

8. Feedback Loops
They do not refer to good or bad. They are named based on their direction of change. Negative feedback loops help to stabilize environmental systems and help systems return to their NORMAL state.

9. Feedback Loop Video

10. Energy Converted in BIOMASS
Primary production = conversion of solar energy to chemical energy in sugars by autotrophs
Gross primary production (GPP) = total amount of energy captured by autotrophs
Net primary production (NPP) = energy remaining after respiration— used to generate biomass
Available for consumption by heterotrophs
Secondary production = biomass generated by heterotrophs from consuming autotrophs
Productivity = rate at which ecosystems generate biomass
Ecosystems differ in net primary productivity
High net primary productivity = ecosystems whose plants rapidly convert solar energy to biomass

11. Biomass Video

12. Ecosystems Ecology Crash Course