Who and Where

Who

Figure 2. The Ctenophore Colobonema (Image from: MBARI)

Bioluminescence, whilst found in a few terrestrial species, is predominantly a marine phenomenon, as 80% of the 700 genera known to contain bioluminescent species are found in the marine environment (Shimomura 2006).  These species come in all shapes and sizes ranging from microscopic bacteria and dinoflagellates, the most abundant bioluminescent organisms (Widder 1999), to crustaceans and fish, which dominate the bioluminescent community in terms of biomass (Herring & Widder 2001). In regards to the phylum with the highest proportion of bioluminescent species, the ctenophora (Comb Jellies) easily win (Widder 2010).

Where

Whilst bioluminescent organisms can be found at all depths of the ocean, perhaps the depths at which it is most important are those below 1000m where no visible light penetrates (Widder 2002). Light in the ocean is reduced ~10-fold with every 75m of depth until the visible light disappears completely below 1000m (Widder 2002). As light and depth are reduced the importance for synthetic light becomes more apparent by the increased  proportion of bioluminescent organisms. This is emphasized by a survey of Burmuda’s deep sea fishes, which indicated that the percentage of bioluminescent fish between the depths of 500 and 1000m could be as high as 97% (Beebe 1937). Due to the low availability of food in  deeper waters, many of these species along with deeper species will migrate to the surface waters at night in order to feed on the high densities of plankton and other small organisms feeding on the plankton (Widder 2002).

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