Open Korth Atlantic 



The percentages of total observations of biolumlnescence from the 

 open ocean of the Worth Atlantic west of 30 W for three-month periods are 

 as follows: 



January through Mairch 2k'fo 



April through June 385^ 



July through September 27^ 



October through December-- 11^ 



The percentages of total observations for the three types of displays in 

 this region axe as follows: 



Sheet type 52^ 



Spark type ih^o 



Glowing-ball type 3^ 



The most liiminescence occurs in close proximity to regions in which 

 "mixing" occurs, such as the front between the Giilf Stream and the cold 

 Labrador Current. Sheet-type biolumlnescence predominates in the spring; 

 both sheet- and glowing-ball luminescence occur with equal frequency in 

 summer in the western North Atlantic. 



Sheet-type displays, which are predominant in the region of "mixing," 

 become less frequent eastward from 30 w, whereas glowing-ball displays 

 gradually increase in this direction. Glowing-ball displays have been 

 reported ^k percent of the time in this portion of the North Atlantic, 

 most frequently in the spring. Sheet-type displays have been recorded 

 about 27 percent of the time and are most often seen from April through 

 September. Spark-type displays have been observed I9 percent of the time, 

 mostly from July through December. 



The Sargasso Sea, noted for its floating vegetation, is, however, an 

 impoverished area with regard to other forms of marine life. As a con- 

 sequence, very little bioliominescence has been observed there. About 

 65 percent of the few reported observations were made from January through 

 June and 35 percent during the other half of the year. Although few in 

 niomber, some very strong displays have been reported, especially on the 

 fringes of this vast eddy. In I9O5 observers on board the scientific 

 yacht PRINCESS ALICE observed a bright luminescent wake as they sailed 

 through the western portion of the Sargasso Sea. The luminescence was 

 globular in form and was caused by large niombers of Pelagia noctiluca , a 

 luminescent medusa noted for its green lu mi nescence. 



In the coastal waters of various island groups, such as the Azores 

 and the Canaries, luminescent displays occur during all seasons. Most 

 of the luminescence observed is caused by large shoals of jellyfishes 

 and tunicates carried into the area by prevailing currents. Around the 

 Canary Islands, biolumlnescence has been observed most frequently during 

 the spring and autumn, whereas in the vicinity of the Azores the majority 

 of displays occur from April through December. 



