Red tides in Monterey Bay are rarely toxic ,but due to unseasonal reversals in winds that drive upwelling,patchy diatom blooms can occur and mix with the red tides.If these diatom blooms are toxic,this can from a second-order harmful algal bloom that is also a red tides.Recent developments in ocean color algorithms that detect the presence of surface aggregations of phytoplankton or differentiate between diatoms and dinoflagellates can improve monitoring efforts of these toxic or nuisance organisms.This capability would enhance the observation potential for warnings of compromised coastal water quality and would influence decision making for managing coastal ecosystems.