The only recognizable living elements in mid-water are the macroplankton. The 

 "snow" is probably composed of radiolarians, diatoms, and coccoliths. Clusters of di- 

 atoms observed and collected at shallov/ pelagic depths of water off California re- 

 semble the snow and mist observed from the bathyscaph window. Often, elongate floes 

 hang vertically in the water. Some long threads of mucus-like material, probably of 

 animal origin, appear like broken medusa tentacles. Aggregates of many small or- 

 ganisms, such as radiolarians and diatoms, might well serve as effective sound ab- 

 sorbers and scatterers and will be investigated further. 



Using the lamps intermittently at about every 100 meters, it was found that there was 

 an increase in the amount of "snow" between 450 and 600 meters. Suspended ma- 

 terials throughout the water column varied in size from diffuse clusters to minute flecks 

 the size of a pea. Below this layer there was a reduced concentration. Scattering quan- 

 tities appeared to remain virtually unchanged between 600 meters and the sea floor. 

 No clear area free of suspended matter was noted near the sea floor as has been re- 

 ported by observers using the French bathyscaph.^ 



The great concentration of material at the boundary between darkness and twilight 

 coincides quite closely with the depth usually occupied by the deep-scattering layer. 

 Here it was anticipated that the large macroplankton organisms that are considered 

 responsible for the deep-scattering layer might be found. Although an effort was made 

 to view macroplankton at this level, no animals active enough to make the great ver- 

 tical migrations, characteristic of scattering layers, were noted. Isolated individuals of 

 medusae, salps, and phosphorescing animals of undetermined species could hardly be 

 construed as being active or abundant enough to produce a migrating deep-scattering 

 layer. Unfortunately, no echo-sounding equipment was available aboard the Italian 

 surface vessels to provide a record indicating the presence of such a layer prior to our 

 dive. 



When the artificial lights were not in use it was possible to detect bioluminescence 

 produced by planktonic animals. This phenomenon was found to be slight and only 

 great enough to reveal that some organisms possessing this capacity were in the water 

 column. Momentary flashes of bluish-white or greenish-white were noted from 350 

 meters to the bottom, with the greatest activity between 450 and 600 meters. The move- 

 ment of the bathyscaph through the water did not, by tactile stimulation, incite an 

 abundance of bioluminescence. However, the mass of water carried behind the moving 

 bathyscaph on the ascent possessed more phosphorescence than the undisturbed water 

 beyond its influences. Occasionally, a chain of salps or a large medusa would become 

 entangled in the rigging of the bathyscaph. The animal would then glow brightly for a 

 long period. It is concluded that only a few organisms capable of illuminating them- 

 selves were present, as Piccard indicated that during the 1956 dives made in the same 

 area at comparable times a spectacular display of phosphorescence was noted. The 

 principal sources of illumination at that time were salps. A vertical distribution of 

 bioluminescence was comparable to the distribution of "snow," as regards uniformity, 

 below 600 meters, with the highest concentration in the water column between 450 and 

 600 meters. Bioluminescence could be observed on the ascent up to the 350-meter level. 

 As on the descent, the ambient light above this level tends to nullify the effectiveness 

 of the artificial lights. 



1 Peres, J. M. and Picard, J., "Observations Biologiques EfFectue'es au Large de Toulon avec le Bathy- 

 scaphe F. N. R. S. — 3 de la Marine Nationale," Inslitut Oceanogrophique, Monoco. Bulletin, no. 1061, 

 p. 1-8, 1955. 



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