1. Ecosystems

2. Ecosystem:  All the organisms in a community plus abiotic factors
 ecosystems are transformers of energy& processors of matter.
 Ecosystems are self-sustaining
 what is needed?
 energy
 producers
 cycling of nutrients

3. Energy budget of ecosystems
 Production by autotrophs sets energy budget for an ecosystem
Marine
light, temperature
nutrients
 depth
Terrestrial
light, temperature
Moisture
 latitude & climate
 nutrients

4. Nutrient Cycling
Decomposition connects all trophic levels

5. Energy transfer
~10% efficiency
Nutrients
Recycled by…

6. OK- Time for some definitions here…..
Primary Productivity-
“the amount of light energy converted to chemical energy.”
Defined in terms of either:
“G.P.P.”
Gross Primary Productivity-
Determined by O2 production
Or….
“N.P.P.”
Net Primary Productivity-
Determined by
Biomass of dry wt. added
(GPP – respiration)
g/m2/yr
Limiting factors:
Sunlight
Precipitation
Nitrogen & Phosphorus
Obviously varies greatly by biome……

7. Primary production Where is productivity highest per square meter?
Total on Earth?

8. Regional annual net primary productivity
Mapping chlorophyll density by satellite

9. Too much of a good thing? Eutrophication High Phosphorus
Algae “over-produce”
Lots of Algae die
Decomposers consume
all the oxygen.
(P is limiting nutrient)

10. Secondary Productivity
“rate that CONSUMERS convert chemical energy into
their own biomass.
Energy flow THROUGH an ecosystem, it does NOT cycle!!
Efficiency:
Remember the 10% rule
“only about 10% of energy is transferred from one trophic level to the next”
1__
10000 1
1000 1_
100 1 10 1

11. But speaking of
CYCLES….

15. Even though the atmosphere is over 70% Nitrogen
Can NOT be assimilated in its elemental form!
Ultimately needs to be a Nitrate!
This bacteria is called
“Rhizobium”
Note that this is a different pathway that uses a different set of bacteria.
In fact, 3 completely different classes
of bacteria!!

16. Another way in which molecular nitrogen is modified is via the discharge of lightning.
The tremendous energy released by the electrical discharges breaks the strong bonds between nitrogen atoms, causing them to react with oxygen.
lightning
N2 + O > 2 NO (nitric oxide)
The nitrous oxide formed combines with oxygen to form nitrogen dioxide.
2 NO + O > 2NO2
Nitrogen dioxide readily dissolves in water to product nitric and nitrous acids;
2 NO2 + H2O > HNO3 + HNO2
Keep in mind that less than 5% of the atmospheric nitrogen gets fixed in this way…

17. Biomagnifications

18. Trendline explained!