| Summary: | The temporal and depth variability of stimulated bioluminescence at 59°N 21°W in the North Atlantic was measured by two bathyphotometers (BPs) during 1991 as part of the ML-ML field program. A moored BP (MOORDEX) obtained a 106 day time series of bioluminescence at a depth of 50 m between 1 May and 15 Aug. A profiling BP (HIDEX) measured bioluminescence in the upper water column during cruises in May and August. Bioluminescence intensity cycled in an approximate 20 day pattern, with the mean intensity of individual flash events increasing from May to August. The shift of the distribution of flash kinetics to larger values suggested a change in the population assemblage of luminescent organisms. Integrated water column bioluminescence was 7 times higher in August than May, with a mean value of 7.2 x 10 15 quanta s -1 m -2 , although there was no significant change in mean vertical distribution. During May, integrated chlorophyll a fluorescence was correlated with integrated biolum.
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