Distribution of bioluminescence and plankton in a deep Norwegian fjord measured using an ISIT camera and the Digital Underwater Video Profiler

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Bioluminescence and plankton profiles were obtained using a downward-looking ISIT low-light camera and the Underwater Video Profiler system in Sognefjord, Norway. The profiling systems were lowered by CTD wire and recorded continuously from the surface to a depth of 1000 m. The former system delivered the vertical distribution of mechanically stimulated bioluminescent signals while the second provided the vertical distribution of undisturbed marine snow and zooplankton. The number of recorded bioluminescent events showed a maximum of 36.3 mean counts for 50 m depth range between 300 and 750 m depths and was positively correlated with the vertical distribution of copepods and negatively with density of marine snow particles (<0.5 mm). The most likely cause of the bioluminescence was the presence of bioluminescent metridiid copepods.