California Sea Grant College Program

Decisions about recreational beach closures would be enhanced with better estimates of surfzone contaminant transport and dilution. New in situ methods, developed here, for measuring fluorescent Rhodamine WT dye tracer in the surfzone increase the temporal and spatial resolution over previous techniques. Bubbles and sand suspended by breaking waves in the surfzone interfere with in situ optical fluorometer dye measurements, but turbidity correction reduces root-mean-square dye concentration errors to < 5% of dye concentration magnitude.