This really depends on the amount of light around the algae.
To get the feeling of the relationship between light and photosynthetic rate, i.e. oxygen production please refer to basic scientific literature such as Teiz and Zeiger "plant physiology" - chapter nine photosynthetic irradiance curves.
In addition to the answers above: see, for an instance, Fig6b in the paper attached.
Generally, the cell density, irradiance, physiological condition (a stress/a limitation presence), CO2 availability are among the factors affecting production of O2 by a microalgal culture.
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