Final answer:
To calculate the Net Primary Productivity (NPP) of a lake, you need to determine the difference in dissolved oxygen (DO) concentration between the light-exposed bottle and the dark bottle. The NPP is the difference between the rate of carbon fixation by photosynthesis (P) and the respiration rate (R). To calculate the NPP in mgC/L/day, you need to convert the DO concentrations to carbon using a conversion factor and then calculate the difference.
Step-by-step explanation:
To calculate the Net Primary Productivity (NPP) of a lake, you need to determine the difference in dissolved oxygen (DO) concentration between the light-exposed bottle and the dark bottle.
The NPP is the difference between the rate of carbon fixation by photosynthesis (P) and the respiration rate (R). In this case, the DO readings after 3 days were 8.7 mgO2/L for the light-exposed bottle and 3.2 mgO2/L for the dark bottle.
The initial DO reading was 6.3 mgO2/L. To calculate the NPP in mgC/L/day, you need to convert the DO concentrations to carbon using a conversion factor and then calculate the difference:
Step 1:
Convert the DO concentrations from mgO2/L to mgC/L using a conversion factor of 1.44. Multiply the DO concentrations by 1.44 to get the carbon concentrations:
Initial DO concentration = 6.3 mgO2/L x 1.44 = 9.072 mgC/L
DO concentration after 3 days (light-exposed bottle) = 8.7 mgO2/L x 1.44 = 12.528 mgC/L
DO concentration after 3 days (dark bottle) = 3.2 mgO2/L x 1.44 = 4.608 mgC/L
Step 2:
Calculate the difference in carbon concentration between the light-exposed and dark bottles:
Difference = Carbon concentration after 3 days (light-exposed) - Carbon concentration after 3 days (dark)
Difference = 12.528 mgC/L - 4.608 mgC/L = 7.92 mgC/L
Step 3:
Divide the carbon difference by 3 (the number of days) to get the NPP:
NPP = Difference / 3 days
NPP = 7.92 mgC/L / 3 days = 2.64 mgC/L/day