Pyrosoma lijminescence have been reported, such as red, orange, yellow, 

 and white light, but these result when the organisms are overexcited or 

 dying. The light normally given off in the sea is bluish green or green. 

 In colder water luminescent salps often are in great abundance and may 

 be present as individuals or in great chainlike aggregations. They 

 luminesce blue or green. 



Except for the above organisms, the majority of luminescent forms in 

 the ocean rarely occur in great enough numbers to create marked surface 

 displays. However, some of these may create displays at certain times 

 and places. Some seaworms may luminesce during their spawning periods 

 when they swarm in svirface waters, and the resulting light may be very 

 strong. The lights Columbus observed on the night preceding his landing 

 on San Salvador may have been caused by the luminescent worm Odontosyllis . 

 Other forms, such as the deep-sea squid Watasenia scintillans (Japanese 

 firefly squid), may congregate in large numbers on the surface during the 

 spring, causing displays. Microscopic radiolarians occasionally may im- 

 part a weak luminescence to the ocean. 



TYPES OF BIOLUMIWESCEWT DISPLAYS 



Biolumine scent displays may be classified according to their appear- 

 ance. The observations presented in this report have been grouped into 

 three general descriptive categories based, with some modifications, on 

 the types proposed by Tarasov (1956). We have named these three: sheet 

 type, spark type, and glowing-ball or globe type. 



The sheet-type display is the most common type observed in coastal 

 waters and is caused by masses of dinoflagellates or bacteria. Tairasov 

 (1956) referred to this luminescence as spilled or "milky" bioluminescence. 

 The water may appear dully luminescent, and the individual points of light 

 are not resolvable; that is, they give a sort of luminous cloudlike 

 appearance in the water. The color usually is green or blue and in many 

 displays appears white when the organisms are present in great numbers. 

 From this latter appearance the term "milky sea" has been derived. Dense 

 and extensive concentrations of large organisms, such as Pyrosoma , lumi- 

 nescing at the same time, may appear as a sheet-type display, instead 

 of the flashing appearance noted when they are less concentrated. The 

 same effect is produced by large concentrations of euphausiids, as 

 Murray (Thomson and Murray, I885) reported in August I88O while in the 

 Faeroe Straits (Faeroe- Shetland Channel). He noted: "large spots and 

 long bands of milk-white water." The luminescence was caused by count- 

 less numbers of Wyctiphanes norvegica , a luminescent euphausiid. 



Spark-type displays are created by large numbers of luminous 

 euphausiids or copepods. This kind of lianinescence occiors most often 

 in colder waters and only when the waters are disturbed. Liiminescing 

 of the organisms gives the ocean surface a scintillating appearance. 

 The luminescence produced usually is brilliant blue or white, and the 

 light flashes are just resolvable to observers from the deck of a ship. 



