Abstract: Aspects of seaweed bioreactor apparatus, methods, and systems are described. One aspect is a method comprising: scaling a seaweed biomass and a culture medium in a light-transmitting vessel located in a light-controlling enclosure; and sampling or harvesting the seaweed biomass without unsealing the light-transmitting vessel by: causing, with a controller, a light source to output an artificial light into the light-controlling enclosure that illuminates the seaweed biomass; outputting, with a sensor in communication with the controller, sensory data associated with the culture medium; modifying, with the controller, at least one of the artificial light or the culture medium responsive to the sensory data; intermittently mixing and cutting, with the controller, the seaweed biomass in the light-transmitting vessel; and removing a portion of the seaweed biomass from the light-transmitting vessel and the light-controlling enclosure. Related seaweed bioreactor apparatus, methods, and systems also are described.