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Old 01/11/2017, 02:24 PM   #3
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Join Date: Aug 2016
Posts: 527
Thanks for the reply santa monica, although perhaps you did not understand my post.

I'll try to be clearer.

I understand that photosynthesis requires light + water and carbon dioxide.
But carbon dioxide in ocean water, at a pH above 7.4, is almost non-existent as it is almost totally converted into bicarbonates & carbonates. So the algae in my scrubber, for instance, has mechanisms whereby it can obtain the carbon dioxide it needs for photosynthesising from bicarbonates rather than directly taking up co2. Or chemically speaking, it removes the CO2 from HCO3-.

This is why my alkalinity has settled at a lower level (125ppm) than it was before my scrubber screen matured. If I dose bicarb the alkalinity level falls quickly back to 125ppm.

But, without dosing bicarbonate, alkalinity appears to remain at 125ppm while the algae continues to grow strongly. If this is correct perhaps the algae is obtaining CO2 from another chemical other than bicarbonates?

Your list of vitamins, carbs, amino acids etc., are dissolved organic compounds. They are the result of photosynthesis. Carbon dioxide + water + light = carbohydrate plus oxygen. All those compounds on your list contain carbon.

So, can photosynthesising organisms obtain CO2, in ocean water at a pH of 7.4 & above, from the carbon in dissolved organic compounds?

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