An ocean of stars, is it for real?
For those of you that have seen the movie ‘Life of Pi’, I am certain that you would be mesmerized by the various magical scenes shown inside the movie as Pi (the main character) was left drifting on the sea. One of the most magical scenes that struck me was the part where it was at night and Pi woke up to a magically lit ocean before him, filled with luminous creatures of all sorts and whenever he stirred the water, it would brighten up even more, as though he was painting the sea.
Fear not, for those of you that have not watched the movie, here is a picture of the scene and a link to a youtube trailer of the movie, showing the scene that I was referring to at about 2:20.
Having seen that, I was pretty curious at how ‘real’ this scene was, is there really a magically lit ocean? Thus begin my quest for the answer to my question. And to my amazement, there really are patches of light up ocean surface at night, and that it was not simply some chemical reaction happening in the sea, but light produced from planktons that are en masse.
Planktons consist of any drifting organism that inhibits the ocean, providing a source of food for the various larger predators/herbivores in the ocean and there are a large range of zooplankton and single-celled animal planktons that are known to be bioluminescence (in essence, growing brightly in the dark). The most common of which belongs to the Dinoflagellates which are tiny unicellular marine plankton that are able to emit visible light, and there are as many as 61 confirmed types of Dinoflagellates that falls into this category.
These planktons achieve bioluminescence through a series of oxidation reactions set off by a catalyst called luciferase, resulting in a chemical reaction that ‘excites’ nearby particles, causing them to vibrate and generate light, accounting for the glow. These chemicals involved are usually broadly classified as luciferins.
Having witnessed and understanding the cause of these strange beautiful lights on the ocean surface at night, it might be pretty hard for anyone to understand what its purpose might be right? After all, it seems counter-intuitive for a prey to want to light itself up and attract the attention of its predators right? Lo and behold, the planktons do not simply light up as and when they want or at random, this bioluminescence is actually stimulated by large lateral movements in the water and could act as a signal to draw predators to the creature that is currently trying to consume the Dinoflagellates! Another alternative possibility would be the flash as a scare tactic to surprise the predator and causing it to worry about other larger predators higher up in the food chain that might be out looking for food at night too. All in all, the two above methods would serve to confer upon the Dinoflagellates that are able to emit light, a greater chance of survival in the wild. It is more than just a cosmetic marvel!
For those keen to find out more, feel free to refer to this youtube video by discovery!
Charlotte L.J. Marcinko, Stuart C. Painter, Adrian P. Martin, John T. Allen, 2012. A review of measurement and modeling of dinoflagellate bioluminescence. Progress in Oceanography, 109, pp 117-129.
K. G. & J. W. Porter, 1979. Bioluminescence in marine plankton: A coevolved antipredation system. The American Naturalist, Vol. 114, No. 3, pp. 458-461.
M. D. Ohman, 1988. Behavioural responses of zooplankton to predation. Bulletin of marine science, 43(3): 530-550.