animals were probably responsible for the damage to the silicone rubber insulation 

 at Test Site II. Silicone-rubber-insulated cables exposed on the sediment at Test 

 Site I were not damaged. 



Possibly because of Its higher water temperature (see Table I), the animals at 

 Test Site II, especially the marine borers, seem to be more active than those at Test 

 Site I. The lower dissolved oxygen concentration found on the sea floor at Test 

 Site II does not seem to have any measurable comparative effect on the animals. 

 The marine borers were found boring into plastic rods, tubes, and tape exposed at 

 Test Site II. No such borer holes were found on identical material exposed at 

 Test Site I. However, the test materials were exposed about 2 months less at 

 Test Site I than at Test Site II. 



Manila rope specimens exposed at Test Site II were heavily infested with borers 

 and about 75 percent of the rope's tensile strength destroyed. Manila rope specimens 

 exposed at Test Site I were attacked slightly by few borers, and the rope's tensile 

 strength was not reduced or destroyed. 



CONCLUSIONS 



The results obtained to date, from 4 and 6 months exposures, on the biological 

 deterioration of engineering materials in the deep ocean indicate that materials 

 such as glass, plastic laminates, plastic ropes, and certain synthetic rubber materials 

 may not be affected; however, additional data from exposures longer than 6 months 

 are needed to provide assurance of relative resistance of these materials to marine 

 organisms. 



Because of severe biological deterioration of untreated wood panels (Including 

 redwood), jute fiber materials, and cotton and Manila ropes, the use of these materials 

 for deep-ocean applications is not recommended. Electrical cables covered with 

 silicone rubber Insulation is not recommended for use on the sea floor in the vicinity 

 of Test Site II, where large deep-sea crabs exist and presumably attack this material. 



FUTURE PLANS 



Investigation of the effects of the deep-ocean environment upon materials Is 

 continuing. 



Test Site I (Nominal Depth of 6,000 Feet) 



STU 1-1 with over 1,000 test specimens exposed on the ocean floor in 5,300 feet 

 of water for a period of nearly 3 years (35 months) was recovered from Test Site I in 

 February 1965. The materials are being examined for corrosion and biodeterloratlon. 



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