I've never seen the ocean glow, but Katie Spotz did this week. She has been rowing in the Atlantic Ocean for 3 weeks now, getting closer to South America each day. A recent tweet from her:
"Can anyone explain what these glowing specks in the water are? Every night I see them and have no clue what they are"
Bioluminescence in the water has puzzled people for thousands of years, starting with Aniximenes in 500 B.C. Many have guessed over the years.
Are they spirits? In 1688 Pere Guy Tachard, during a cruise to Siam, said:
"We attribute the cause to the heat of the sun, which has, as it were, impregnated and filled the sea during the day with an infinity of fiery and luminous spirits. There spirits after dark reunite to pass out in a violent state..."
Are the glowing specks the spawn or seed of whales? Father Bourzes, a Jesuit missionary in the East Indies said in 1713:
"...in sailing over some Places of the Sea, we find a Matter or Substance of different Colours, sometimes red, sometines yellow. In looking at it, one would think it was Saw-dust: Our Sailors say it is the Spawn or Seed of Whales. What it is, is not certain; but when we draw up Water in passing over these Places, it is always viscous and glutinous...."
Nope. The glow is likely from bioluminescent dinoflagellates—that is, marine plankton that light up. The plankton light up when they sense a predator. The purpose is to attract a bigger predator that will eat the plankton's predator!
For more historical ideas on bioluminescence, see A History of Marine Bioluminescence According to E.N. Harvey.
This video will give you an idea of what bioluminescence looks like. Video footage courtesy OceanLab, University of Aberdeen.
Bioluminescent emissions from a range of zooplankton recorded by the ICDeep ultra low light camera as it travels 15m down through the water column, at a depth of 450m. The bioluminescence is stimulated as the animals impact on a mesh placed 50cm in front of the camera. This video was taken in the Strait of Sicily.