Comparative evaluation of four Chlorella species treating mariculture wastewater under different photoperiods: Nitrogen removal performance, enzyme activity, and antioxidant response

The nitrogen removal performance, nitrogen metabolism enzyme activities, and antioxidant response of four Chlorella species (Chlorella sp., Chlorella vulgaris, Chlorella sorokiniana, and Chlorella protothecoides) were compared under different light: dark (L:D) photoperiods during treating mariculture wastewater. The increase of light duration in the range of 8L:16D to 16L:8D was beneficial to the chlorophyll synthesis of selected four Chlorella species. Chlorella vulgaris was the most effective to treat mariculture wastewater than Chlorella sp., Chlorella sorokiniana, and Chlorella protothecoides. and its microalgae density, photosynthetic activity, and nitrogen metabolism enzyme activity were higher than those of the other three Chlorella species. An obvious oxidative stress in microalgal cells was under 20L:4D photoperiod, which led to a decrease in photosynthetic activity and nitrogen metabolizing enzyme activity. Among the four Chlorella species, Chlorella protothecoides had the highest degree of light-induced stress and ROS accumulation. This study can provide suitable microalgae and optimal photoperiod for treating mariculture wastewater.

Automated summary

The nitrogen removal performance, nitrogen metabolism enzyme activities, and antioxidant response of four species of Chlorella (Chlorella sp., Chlorella vulgaris, Chlorella sorokiniana, and Chlorella protothecoides) were compared under different light: dark (L:D) photoperiods during treating maricultural wastewater. Increasing the light duration from 8L:16D to 16L:8D was found to be beneficial for chlorophyll synthesis in all species. Chlorella vulgaris showed the highest effectiveness in treating maricultural wastewater, with higher microalgae density, photosynthetic activity, and nitrogen metabolism enzyme activity compared to the other species. Under a 20L:4D photoperiod, obvious oxidative stress was observed in microalgal cells, resulting in decreased photosynthetic activity and nitrogen metabolizing enzyme activity. Among the four species, Chlorella protothecoides exhibited the highest degree of light-induced stress and ROS accumulation. This study provides insights into suitable microalgae and optimal photoperiod for treating maricultural wastewater.