A photo-bioreactor system for growing and harvesting photosynthetic organisms includes an interior space partitioned into a plurality of independently controlled reactor cells, each stepped downward along a slope from a first elevation to a second elevation, and a light source coupled to each reactor cell and configured to illuminate the photosynthetic organisms with first and second light-emitting surfaces. The system includes a fluid circulation system coupled to the reactor container and configured to force a continuous flow of fluid through the cell passages.