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This lab explores the impact of temperature and light availability on dissolved oxygen (DO) saturation in aquatic environments. In Part A, we assess how varying temperatures influence DO percentages. Part B focuses on the effects of light intensity on the primary productivity of Chlorella sp. through photosynthesis rates. We utilize the Winkler method to quantify oxygen levels, involving a fixation step with manganese compounds and a titration process with starch as an indicator. Calculate net and gross productivity to understand aquatic ecosystems better.
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AP LAB 12 • Part A – Effect of Temperature on DO (dO2) • % Saturation
AP LAB 12 • Part B - Effect of Light Availability on DO • Primary Productivity • Rate of photosynthesis • Chlorella sp. • Set-up • Initial • Dark • Varying number of screens • Calculations • Respiration • I – D • Net Productivity • L – I • Gross Productivity • Net Productivity + Respiration • (L – I) + (I – D) = L - D
AP LAB 12, cont • Winkler Method • Measures the amount of I2 in solution → proportional to O2 • Fixation Step • O2 oxidizes Mn(OH)2 • Sulfamic acid is added to fix the reaction, form I2 • Titration Step • Starch is used as an indicator to quantify the concentration of I2
