In coastal waters around the globe, harmful algal blooms are becoming more intense and more frequent, endangering both human health and wildlife. In California, one of the most problematic harmful marine algal toxins is domoic acid, which has caused mass deaths of sea lions and seabirds and is commonly detected in fish caught by anglers. This project focuses on more fully understanding how certain kinds of harmful algal blooms form and spread off California, the goal being to forecast these potentially serious public health threats. The major effort to date has been to combine and expand existing domoic-acid forecasting models for the Santa Barbara Channel and Monterrey Bay, using new monitoring and NASA remote sensing data, as well as numerical model fields. A similar but much simplified modeling effort is underway for Alexandrium catenella, which produces the toxin that causes paralytic shellfish poisoning. In 2013, researchers sought to identify the relative importance’s of surface seawater temperatures, surface salinities, micronutrient concentrations and their ratios, ocean color, freshwater inputs and upwelling indices in “driving” bloom formation and toxin production. This information will be used to determine the number of regional models that need to be “stitched” together to accurately predict blooms off all of California. The California Department of Public Health and the California Program for Regional Enhanced Monitoring of PhycoToxins are providing data needed to develop and validate the model. In addition to the modeling work, OPC funding provides support for continued collection of field data and for the development of several outreach tools, including various web portals to aggregate all of California’s harmful algal bloom projects, present bloom forecasts to managers and health officials, and to help implement a coordinated response network.