Figure 1. Flash kinetics for bioluminescent emissions of plankton recorded in a bathyphotometer.

(a) Shown is a representative luminescent emission from the copepod Metridia longa (blue line), with parameters we used to create taxonomic signatures for in situ identifications of this and other luminescent plankton (see Table 1). Parameters are maximum bioluminescence (BL_max), average bioluminescence produced during the emission (BL_mean), time until the emission reached maximum (T_max), and cumulative sum of bioluminescence produced until the maximum (Σ_max; blue shading). Inset are representative luminescent emissions from dinoflagellates (green line), ctenophores Mertensia ovum (red line), and krill Thysanoessa spp. (grey line). (b) Examples of underwater bathyphotometer (UBAT) time series, showing individual flashes flagged with red circles at their peaks. These data are from the same noontime cast, with the upper panel showing a 4 min stop at 1 m, and the lower panel a 4 min stop at 80 m. Note the difference in scale, and in turn flash intensity, between these two depths across an ecotone (see Results).