Seas turn Milky White

We were cruising somewhere in the Indian Ocean, two days shipping from Djibouti. Two of us were on the deck of the research vessel in the middle of the night because instruments had to be dropped into the ocean at regular intervals. It was then that we saw the sea turning almost milky white. The captain had seen such a phenomenon before but none of us had.  That was about 18 years ago and although we were all familiar with the bioluminescence common in the ocean we could not find out what was turning the seas milky.

Now satellite images of milky white seas in the Indian Ocean have been discovered by scientist  Steve Miller and his colleagues of the US Naval Research Laboratory. In a new publication, Miller and colleagues describe finding a sighting of milky white seas from a ship in the Indian Ocean in 1995 near Somalia. They then looked for satellite images taken of this area at the time. The images did capture the event, and subsequent analyses showed that the glowing water covered 15,400 square kilometers. The milky white glow continued for three nights but it moved with the currents.

A large population of glowing bacteria called Vibrio harveyi, which live together with microscopic algae, probably generated the soft, white light. This phenomenon is known as bioluminescence. This is light produced through chemical reactions in an organism. Quite a few organisms produce bioluminescent, some on land such as fungi and fireflies both of which are found in Seychelles, but mostly in the sea.

At sea bioluminescence is a common occurrence in the bow wave and wake of a ship The usually greenish or bluish, iridescent glow is caused by tiny organisms called dinoflagellates, which are single celled algae. The algae are mechanically excited by the passage of ships to produce chemical reactions leading to light. Bioluminescence is a fascinating phenomenon and it is the only source of light in the deep ocean. It usually does not exist in freshwater areas.

The milky white sea is not a common occurrence and until now it was not known what caused it. There have been accounts from sailor for many years but no one had investigated it. The scientists say that as satellite technology gets more sophisticated they hope to be able to detect milky seas as they happen and then can actually go to the area and find out what is going on. You can help as well. Anybody who has seen this phenomenon around Seychelles can call me with the details so I can send the information to the American researchers working on it.


By Nirmal Jivan Shah, published on the People Newspaper, Seychelles on 6th October 2005.

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