Vinyl Tube (NCEL No. 387) . The borers did not penetrate into yellow vinyl 

 tubing; however, about 150 borers per square inch of surface had attempted to 

 penetrate into the plastic on the lower 2-1/2 inches of the tube exposed near the 

 sediment, as evidenced by white etch marks (Figure B-17). 



Vinyl Tube (NCEL No. 389), Moderate numbers of small, shallow borer holes 

 were found on the tubing. 



0.015-Inch Insulation Over No. 16 Wire 



The 15-inch-long stressed and nonstressed silicone-rubber-insulated wire 

 specimens exposed next to sediment and another identical set exposed to sea water 

 about 3 feet above the sediment were deteriorated by marine animals. Microorganisms, 

 amphipods, and crabs found on the STU may have been responsible for the destruction. 

 The specimens of silicone rubber insulation exposed near the bottom were heavily 

 damaged, exposing the bare wire to sea water in several areas (Figure B-18). 



Neoprene and GR-S rubber insulations exposed near the sediment were also 

 slightly damaged by the nibbling action of marine animals. However, a set of 

 identical stressed and nonstressed neoprene and GR-S rubber insulation exposed 

 about 3 feet above the sediment were not so damaged. 



The stressed and nonstressed polyethylene and polyvinyl chloride insulation 

 exposed near the sediment and 3 feet above the sediment were not damaged. 



The results of insulation resistance and voltage breakdown tests on the 

 recovered wire specimens are presented in Table IV. A long-term laboratory study 

 on the effects of deep-sea microorganisms on these rubber and plastic insulations has 

 been reported.' 



Insulated Cables — Single and Multiconductor 



Of the various insulations of varied thicknesses over single and multiconductor 

 wires, the l/16-inch-thick silicone rubber insulation exposed over the sediment was 

 severely damaged by nibbling and chewing, presumably by amphipods and crabs. Some 

 areas of the insulating material were completely destroyed, exposing the bare wires 

 to sea water (Figure B-18). The silicone rubber insulation exposed about 3 feet above 

 the sediment was also attacked by marine animals but not as severely as the one 

 exposed near the sediment, 



A few borers had penetrated slightly into the silicone rubber (Figure B-19) and 

 nylon insulating materials. The borer holes found on the silicone rubber were exposed 

 to the sea-water environment. The borer holes found on the nylon, however, were 

 exposed in an area underneath the wooden bait piece. The bait piece exposed near 

 the sediment was severely damaged compared to the piece exposed about 3 feet above 

 the sediment (Figure B-20), 



The cable insulations other than silicone rubber and nylon insulation were not 

 damaged by marine animals or affected by the deep-sea environment. 



13 



