Scott Doney's session from MIT's 12.742 Marine Chemistry covers primary production in the ocean water column, examining how phytoplankton use light and dissolved inorganic carbon to build organic matter and release oxygen. The lecture works through the environmental controls on this process, including light availability, nutrient supply, and temperature, and situates photosynthesis within the broader chemical cycling of the ocean. Running 79 minutes as part of the Fall 2006 course, the session builds on earlier material in the series and treats primary production as a chemical process governed by measurable physical constraints rather than a purely biological topic. It fits within MIT OpenCourseWare's release of selected recorded sessions from the course, taught for students studying ocean biogeochemistry.