CONCLUSIONS 



1. The following materials are susceptible to total biological destruction within a 

 relatively short time: untreated wood, including tropical wood; manila and cotton 

 ropes; and burlap (jute fibers). It is assumed that wood panels treated with wood 

 preservatives which are effective against borers in shallow waters may be equally 

 protected against deep sea borers. However, exposure tests in the deep sea should 

 be conducted to confirm this. 



2. The following materials were not attacked and, therefore, are probably not 

 susceptible to biological deterioration at this particular deep ocean site: PVC pipe; 

 butyl rubber, neoprene rubber, natural rubber, PVC, nylon, FEP, GR-S rubber, and 

 Teflon electrical cable insulations; various plastic laminated sheets; glass microscope 

 slides; rubber vacuum tubing; nylon nuts and bolts; nylon and polypropylene ropes 

 and ethyl cellulose cable clamps; and plastic electrical insulation tape. 



3. Some of the 3-foot-long plastic rods and tubes which were damaged by borers in 

 the area of the wood bait pieces can probably be used in the deep ocean if they are 

 not placed in direct contact with wood. Other plastic rods and tubes which were 

 susceptible to direct attack by borers from the seawater environment are not recom- 

 mended for such use. Plastics for deep ocean use should be selected with caution, 

 because some will absorb considerably more moisture than others and thereby change 

 their physical characteristics. For example. Teflon and polyethylene rods absorbed 

 the least amount of water, while cellulose acetate rods, phenolic laminates, and 

 nylon rods absorbed considerable amounts of water by comparison. As a result, the 

 hardness of some of the plastic materials had changed considerably. 



COMPARISON OF TEST SITES I AND II 



Since this is the last of a series of reports on biodeterioration of materials 

 exposed to date at Test Sites I (6,000 feet nominal depth) and II (2,500 feet nominal 

 depth), findings of significant differences at these two locations will be briefly 

 discussed. In order to better compare the results on biodeterioration at the two 

 locations, identical materials were placed on each of the six STUs. However, there 

 were a few different items placed on each STU, depending upon the availability of 

 the test materials at the time. 



Factors Found Common at Both Locations 



The following marine organisms were found at both STU sites: (1) slime bacteria, 

 molluscan borers, hydroids, tubeworms, pectens, and sea anemones; (2) some unknown 

 marine organisms which had deteriorated the surface of silicone rubber electrical 



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