Nutrient conversions and limitations a) Based on the following equation from cla

Question

Nutrient conversions and limitations

a)

Based on the following equation from class, if a phytoplankton takes up 10 ?mol of HNO3, how many ?mol of O2 will be generated? (Note that 1 ?mol = 10?6 mol)

energy
106CO2 +16HNO3 +H3PO4 +122H2O ???? [(CH2O)106(NH3)16(H3PO4)]phyto +138O2

b)

In the subarctic N. Atlantic Ocean before the spring phytoplankton bloom, typical concentrations of nutrients are 6 ?M HNO3 and 0.3 ?M H3PO4. Assuming that the above equation holds, which of these two nutrients is limiting to phytoplankton growth at the beginning of the spring bloom assuming that light, water, and CO2 are all abundant? In other words, which of the two nutrients will run out first? (Note that 1 ?M = 10?6 M, where 1 M = 1 mol/liter.

c)

Based on complete consumption of the limiting nutrient found in part B) above, how much phytoplankton biomass will be produced per liter of seawater? Give your answer in ?g per liter or ?M.

Explanation / Answer

a)

from the given equation, we can see that

16 umols of HNO3 gives 138 umols of O2

so, 10 umols of HNO3 will give 138 * 10/16 umols of O2 (by unitary method)

so, answer is 86.25 umols of O2 will be produced.

b)

from the reaction we can see that, 16 umols HNO3 reacts with 1umol of H3PO4 to give 1 umol of phyto

so, lets multiply each item with 0.3, to get 0.3 umol of H3PO4

now, we have 4.8 umols of HNO3 reacting with 0.3 umol of H3PO4 to give 0.3 umol of phyto

so, we can see that 0.3 umol of H3PO4 is consumed but 6 - 4.8 = 1.2 umol of HNO3 is still remaining

So, H3PO4 is the limiting nutrient or will get consumed first.

c)

0.3 umol of H3PO4 will give 0.3 umol of phyto (as explained in part b)

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