Harmful algal blooms (HAB) have been a recurring problem in King Harbor of the City of Redondo Beach in recent years. In 2005, a red tide resulted in a massive fish kill, and created a nuisance for commercial and recreational use of the harbor. It took several weeks for the incident to subside and for the ecosystem to return to normal. Several potentially problematic species of algae again bloomed during 2006, and seven bloom-forming species were isolated and cultured. Beginning in January 2007, the Networked Aquatic Microbial Observing System (NAMOS), which is comprised of both mobile and static sensing platforms, has been employed periodically in the harbor area to monitor phytoplankton population dynamics. A robotic boat is able to provide vertical profiles of critical environmental data including chlorophyll, temperature, salinity and dissolved oxygen throughout the harbor, while continuous recordings of chlorophyll concentration, dissolved oxygen, CTD, and turbidity are gathered by sensors at both surface and near bottom in different locations in the harbor.The combined use of static and mobile nodes constitutes an effective monitoring and early warning system for HABs. NAMOS has proven an excellent tool for providing excellent contextual data for experimental studies of bloom-forming species of phytoplankton. Field and lab experiments were conducted in conjunction with the deployment of the sensor network in order to examine environmental triggers for algal blooms in the harbor.