Biochemistry of algal growth

Living algae is produced from CO₂, PO₄, NO₃ or NH₄ and H₂O (plus many other minerals in much smaller quantities) as shown in the following equations which represent photosynthesis:

106CO₂ + 16NO₃ + HPO₄ + 122H₂O + 18H⁺ --------> C₁₀₆H₂₆₃O₁₁₀N₁₆P₁ + 138O₂

or

106CO₂ + 16NH₄ + HPO₄ + 108H₂O --------> C₁₀₆H₂₆₃O₁₁₀N₁₆P₁ + 107O₂ +14H⁺

Note use of NH₄ as N source produces acid that consumes TA whereas use of NO₃ uses up H protons so increasing TA.

The overall effect however is a very large consumption of CO₂ which drives up pH. Consumption of 1 CO₂ molecule means that 2 H⁺ protons are removed from the water, so the effect from CO₂ consumption is far greater than from other effects.

The CNP molar ratio of algae is 106:16:1. The molar C:N is 6.625:1.