Observations of planktonic bioluminescence in the euphotic zone of the California current

The distributions of bioluminescence, temperature, salinity, oxygen, pH, and chlorophyll a were measured at 10 m intervals, to a depth of 100 m at a station in the California Current from 17 to 22 July 1982. The distribution of bioluminescence showed a marked day-night change which was consistent over the sampling period. The nighttime maximum was at the surface, and the daytime maximum was between 30 and 40 m. The shapes of the day and night distributions were independent of the absolute intensity of bioluminescence and were also insensitive to advection, as inferred from changing temperature-salinity relationships. The nighttime depth distribution broadened during a period of high wind. Day to night differences in the color spectrum at the depth of maximum bioluminescence suggest that the luminescent organisms differed from day to night.