Luminous Life - The Glittering Sea

A bioluminescent hydromedusa.

So far, our examination of bioluminescence has focused on land dwellers - fungi, worms, various insects. As rare as the ability is here on dry ground, up to 90 percent of ocean life is capable of producing light. Against the backdrop of a black sea, life forms use self-generated light to hunt, find mates and defend themselves.

Red tide bioluminescence taken at midnight at a
Carlsbad, California beach. Image by Flickr user msauder.

And it starts at the bottom of the food chain. Some forms of plankton can create light, as in the image above. The sea appears to glow, especially when disturbed, and if conditions are right, the phenomenon can cover such a large area that it can be seen from space.

A ctenophores light display is actually diffraction
of ambient light, not bioluminescence.

Even when sea creatures are not producing their own light, they are able to make use of what dim light reaches them. Some organisms can put on quite a display by reflecting any existing light.

Blackdevil angler fish with bioluminescent lure.
Image by Edith Widder/HBOI.

As beautiful as a bioluminescent display can be, it can mask a hungry predator. The angler fish lights its lure to draw in prey. This little fishy looks like it swam straight out of a bad dream.

We can thank Edith Widder for bringing us this scary guy. For more of her images and the challenges she faces trying to capture shimmering sea creatures and photograph them, check out this link.

To go with the still images, here are 2 short videos of bioluminescence in action. The first one features a magnificent jellyfish shown in both direct light and in darkness.



This second video is of a dazzling comb jelly that almost appears to be an alien life form.



As I was thinking about how, even in the darkest depths of the ocean, the sea inhabitants were using their own light, it made me wonder why they would develop the ability in the first place. Why not develop some other sensory method to accomplish all the tasks they need to accomplish? Electrical signals, pressure changes, scent, hearing - something that didn't depend on light, which is so noticeably absent in that environment.

Not being a biologist, I can only speculate that the rhythm of the Earth's day/night cycle was a powerful influence on evolution, even when life was found only in the sea. The dichotomy was so strong that life forms internalized it so that even in the darkness, light can exist.