Mariner notes exciting bioluminescent display

The Indian Ocean produces the most spectacular displays of a marine phenomenon called bioluminescence. This is a gentle blue or green light that appears in the ocean at night. It is a bit like the marine equivalent of fireflies, only on a much grander scale. For years I have been a casual but fascinated observer of this natural display, but nothing could have prepared me for the show that I observed on November 4, 1997.

I was standing watch on the oil rig supply ship Ocean Worker. At 0300 local time we were at 14° 45′ N, 96° 25′ E, about 70 miles south of the entrance to the Rangoon River. It was a dark, overcast night with rain in the area. The water depth was 45 fathoms and the wind was blowing from the northeast at 20 knots. Three hundred miles to the southeast lay tropical cyclone Linda.

Feeling cramped and in need of some fresh air, I opened the wheelhouse door and stepped out onto the bridge wing. I was standing just 30 feet above sea level. The first thing I noticed was hundreds, maybe thousands, of bioluminescent masses in the water all around the ship. They were pulsating in unison at an estimated 80 cycles per minute.

I had seen similar displays in these waters, although not on such a large scale. I was sufficiently impressed to summon the lookout, Samuel Apaya, who was still inside the wheelhouse. I know this man does not drink or smoke and is a credible witness. By the time Apaya made his way outside, the entire surface of the water had changed appearance. Not only could we see bioluminescent masses, but the sea surface was pulsating with bright, rotating wands of green energy. We both looked upwards, half expecting to see a flying object, but there was nothing in sightno aircraft, ships, yachts, lighthouses, submarines, or fishing boats. We had no clue as to what would cause the weird display of lights in the sea all around us as far as we could see.

I was wild with excitement. I reached for my camera, although I knew that no camera could capture what I saw with my own eyes. How, then, could I record this amazing event for posterity? With sweat on my brow, I reached for my pen and began taking notes.

Within five minutes the bioluminescent display turned off as quickly as it started. I estimate that the wands of light were moving at 100 knots, maybe more. The interval between the light was barely a second. Even as a seasoned mariner, I was very impressed by what I had seen. So was Apaya, who cosigned my official report of the event.

Nautical publications mention sightings of "bioluminescent wheels," but no explanation is offered. Has anyone else witnessed such an event?

Norm Fraser is a master mariner who operates a marine surveying business in Queensland, Australia.

Dr. Michael I. Latz, a researcher at Scripps Institution of Oceanography, Marine Biology Research Division, in La Jolla, Calif., replies:

Mr Fraser’s letter makes for interesting reading. As of 1985 there were approximately 230 reports of phosphorescent wheels or moving bands of luminescence. These reports are summarized in an article written by P. Herring and P. Horsman in Marine Observer vol. 55, 1985).

All of the reports originate from tropical areas, with most (95%) from the Indo-Pacific. It is interesting that there are few reports from sailing ships, either modern or before engines were used. In fact, there are no reports from local fisherman or other small boat traffic. This suggests that perhaps the ship itself is involved in the production of light. Of the reports in which the frequency of pulsing is given, more than half were between 60 and 120 per minute. Fraser’s observation fits right into this range. In cases where the engine rpm was noted, the flashing rate was similar to the engine rpm. A critical experiment, which has never been done, would be to stop the engines. Not to take away from its interesting nature, but Fraser’s report appears to be typical of many others describing bands of luminescence.

By Ocean Navigator