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AP Lab 12

AP Lab 12. Dissolved Oxygen and Aquatic Primary Productivity. In this laboratory you will:. 1.Measure the amount of dissolved oxygen in water samples at different temperatures 2.Analyze the effect of varying amounts of light on primary productivity.

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AP Lab 12

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  1. AP Lab 12 Dissolved Oxygen and Aquatic Primary Productivity

  2. In this laboratory you will: 1.Measure the amount of dissolved oxygen in water samples at different temperatures 2.Analyze the effect of varying amounts of light on primary productivity

  3. Why did the fish that I kept in an aquarium over my radiator die? An aerator was producing a constant stream of bubbles, so they should have had plenty of oxygen.

  4. Dissolved Oxygen Availability • Oxygen is needed for….. • Cellular respiration • Factors that affect oxygen in water • Temperature • Colder holds more oxygen • Photosynthetic activity • More light, more oxygen • Decomposition activity • As organic material decays, microbial processes consume oxygen • Mixing and turbulence: • Wave action, waterfalls, and rapids increase the oxygen • Salinity • More salty, ability to hold oxygen decreases

  5. Primary Productivity • Primary productivity - rate at which photosynthetic organisms produce organic compounds in an ecosystem. • Two aspects of primary productivity: • Gross productivity = the entire photosynthetic production of organic compounds in an ecosystem. • Net productivity = the organic materials that remain after photosynthetic organisms in the ecosystem have used some of these compounds for their cellular energy needs (cellular respiration).

  6. Primary Productivity • Can’t measure directly because photosynthesis/respiration always occurring • We can measure net productivity directly by measuring oxygen production in the light, when photosynthesis is occurring. • We can also measure respiration without photosynthesis by measuring O2 consumption in the dark, when photosynthesis does not occur. • Since net productivity = gross productivity – respiration, we can calculate gross productivity.

  7. Measuring Primary Productivity • Primary productivity can be measured in three ways: 1.The amount of carbon dioxide used 2.The rate of sugar formation 3.The rate of oxygen production • We use method 3

  8. Part A • Measuring dissolved oxygen in water at 3 different temperatures • Measuring oxygen in mg/L • Then determining % saturation using a nomograph

  9. What is the percent oxygen saturation for a water sample at 10°C that has 7 mg O2/L?

  10. Part B • Determining primary productivity for pond samples at different depths • Doing this by simulating different light exposures

  11. Part B results

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