[Nyctohemeral variations of marine bioluminescence in the Mediterranean and the northeastern Atlantic].

Bioluminescence measurements have been made using a bathyphotometer allowing the determination of stimulated light intensities down to 2,000 m depth, in the Mediterranean Sea on the Almeria-Oran front, during the winter 1997-1998, and in the northeastern Atlantic, on the Armorican continental shelf, during summers 1999 and 2000. Bioluminescence is weaker in the Mediterranean than in the Atlantic. In the epipelagic waters, day/night variations appear clearly, stimulated bioluminescence is higher at night than during the day. These diel variations can be explained by vertical migration of bioluminescent organisms and by photoinhibition of dinoflagellate bioluminescence. Fluorescence measurements made at the same time give information about potential bioluminescent sources, autotrophic and heterotrophic.