This invention provides a vessel system and methodology that can be used to promote growth of phytoplankton in the oceans. Unmanned self-controlled wave-powered vessels are equipped with storage units for dispensing a fertilizer, and with sensors to monitor ocean conditions and effects. Fleets of vessels move autonomously by on-board processing of GPS and directional information, piloting a path that is coordinated by a central processing unit. The vessels travel through a defined target area, creating a detailed survey of chemical and biological characteristics that affect grown. The data are processed in a computer model to identify precise locations and precise amounts of fertilizer that will produce the best results. Projected benefits of fertilizing plankton include sequestering CO2 from the atmosphere, and enhancing the marine food chain to improve the fish stock in and around the treated area.