Abstract: A biological cultivation system for the culture of photosynthetic organisms including at least one cultivation chamber permitting exposure of the culture medium to natural and/or artificial light and including; a light transmissive wall or walls defining a gas space; and a culture medium containment area below the gas space; one or more fluid inlets positioned within the culture medium containment area; and one or more gas outlets in communication with the gas space; a control unit operatively connected to a gas flow control device, the gas flow control device controlling the flow of gas in through the fluid inlets and out through the fluid outlets to control the conditions within the cultivation chamber.