[Campbell Biology P.103] Referring to the scatter plot, if the seawater carbonate ion concen... | Practice Question

Referring to the scatter plot, if the seawater carbonate ion concentration is 250 µmol/kg, what is the approximate rate of calcification, and approximately how many days would it take 1 square meter of reef to accumulate 30 mmol of calcium carbonate CaCO3 ?

  • A: Rate: 10 mmol CaCO3/(m^2 * day); Days: 3 days
  • B: Rate: 12 mmol CaCO3/(m^2 * day); Days: 2.5 days
  • C: Rate: 8 mmol CaCO3/(m^2 * day); Days: 3.75 days
  • D: Rate: 15 mmol CaCO3/(m^2 * day); Days: 2 days

Explanation

To solve this, first locate 250 µmol/kg on the x-axis. Follow vertically up to the red regression line, then horizontally to the y-axis to read the calcification rate. The line crosses the y-axis exactly at 10 mmol CaCO3/ m^2 day . Then, to find the number of days, divide the total desired accumulation 30 mmol by the rate: 30 mmol / 10 mmol/ m^2 day = 3 days.