Bioluminescence profile in the deep Pacific Ocean

The vertical profile of bioluminescence at a station hear Hawaii has been measured to a depth of 4300 m using a calibrated instrument with a threshold sensitivity of 400 photons cm−2 s−1. The measured light is dominated by flashes over a very faint ambient background. The median light levels follow an exponential scaling law below 2000 m and decrease at the rate of 1/e per kilometer. Stimulated bioluminescence is observed in the wake of the instrument, even at depth.