1. Chapter 13 Biological Productivity and Energy Transfer

2. Chapter Overview Primary productivity is photosynthesis.
Productivity is globally and seasonally variable.
Feeding relationships are represented by food chains and food webs.
Oceans are being overfished.

3. Primary Productivity Rate at which energy is stored in organic matter
Photosynthesis uses solar radiation.
Chemosynthesis uses chemical reactions.
99.9% of the ocean’s biomass relies directly or indirectly on photosynthesis for food.

4. Photosynthesis

5. Measurement of Primary Productivity
Directly – capture plankton in plankton nets
Measure radioactive carbon in seawater

6. Measurement of Primary Productivity
Monitor ocean color with satellites
Photosynthetic phytoplankton use green pigment chlorophyll
SeaWiFS (Sea-viewing Wide Field of View Sensor) satellite sensor collected ocean color data 1997–2010
MODIS (Moderate Resolution Imaging Spectroradiometer) – current
Measures 36 spectral frequencies

7. Factors Affecting Primary Productivity
Nutrient availability
Nitrate, phosphorous, iron, silica
Most from river runoff
Productivity high along continental margins
Redfield ratio – C:N:P

8. Factors Affecting Primary Productivity
Solar radiation
Uppermost surface seawater and shallow seafloor
Compensation depth – net photosynthesis becomes zero
Euphotic zone—from surface to about 100 meters (330 feet)
Enough light for photosynthesis

9. Light Transmission in Ocean Water
Visible light portion of the electromagnetic spectrum

10. Light Transmission in Ocean Water
Blue wavelengths penetrate deepest
Longer wavelengths (red, orange) absorbed first

11. Light Transmission in Ocean Water
Only 45% of the light energy that hits the surface reaches a depth of 1 meter.
Only 1% of the light energy that hits the surface reaches a depth of 100m.

12. Color in the Ocean
Color of ocean ranges from deep blue to yellow-green
Factors
Turbidity from runoff
Photosynthetic pigment (chlorophyll)
Secchi Disk – measures water transparency

13. Color in the Ocean Coastal and upwelling areas productive
Light green
Eutrophic
Open ocean lacks productivity
Dark blue
Oligotrophic

14. SeaWiFS Image of Ocean Chlorophyll

15. Upwelling and Nutrient Supply
Flow of deep water to surface
Cooler, deeper seawater is nutrient-rich.

16. Upwelling and Nutrient Supply
Areas of coastal upwelling are sites of high productivity.
Western continental margins

17. Upwelling and Nutrient Supply