A photobioreactor comprising a sealed, covered plastic sheeting coated with a thin layer of a highly dense culture of photoautotrophic single celled organism. Carbon dioxide is exchanged from a gas space above the culture through attendant mixing by subtending wave motion. The photobioreactor provides a substantial improvement in processing costs in growth media sterilization as well as reduced expenses related to energy and raw materials, especially carbon dioxide. Capital expenses are reduced by eliminating the need for sparging and compressors for suspending cells and mixing carbon dioxide.