Key concepts are that photosynthesis and respiration in the seawater can change pH and Ω by consuming/producing CO2. Remind students of the reaction for photosynthesis/respiration and of the fact that photosynthesis only occurs in daylight, whereas respiration occurs all the time. This sets students up to identify that the diurnal cycle of pH and Ω in Netarts Bay is created by drawdown of CO2 during the day, when photosynthesis is occurring, which decreases pH and Ω, followed by an increase in pH and Ω at night when respiration is adding CO2 back to the water.

Photosynthesis and Respiration

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