Dave Munger in Seed Magazine:
One of the most alluring visual feasts in the movie Avatar was its alien biosphere of glowing plants and animals. Nearly every living thing on the moon Pandora seemed to shimmer and sparkle—sometimes in response to touch, other times as an expression of emotion. It’s something that separates this magical world of make-believe from the real world here on Earth.
Or is it? While bioluminescent organisms are perhaps not as common in the real world as they are in science fiction, they do exist, in a surprising variety of places. I first encountered them at night on a dock near my childhood home in Seattle. Initially the waters of Puget Sound seemed dark, but dipping a hand revealed a luminous surprise—tiny glowing bits appeared, like underwater sparks, wherever my hand disturbed the water. Then I saw a glowing fish swim by, leaving a luminous trail. The fish wasn’t actually glowing; rather, it was causing tiny bioluminescent dinoflagellates to glow as it passed them. This may be a defense mechanism for the dinoflagellates. Since any movement by their predators causes them to glow, this light may attract other, larger predators that could then do away with the danger.