attached to the STU so that the lower portions would be either near the bottom 

 sediment or buried in it and the upper portions would be exposed to seawater 3 to 4 

 feet above the mud line (Figure 4). 



The 2x6x l/2-inch wood panels were cut from sound lumber, and the surfaces 

 were cleaned with alcohol and then covered with plastic to avoid contamination. 

 The plastic covers were removed Just before the test specimens were submerged. The 

 wood panels were employed to collect specimens of any deep sea fungi and marine 

 borers which may have been present on the ocean floor. 



The sections of the 3-foot-long plastic rods, tubes, and pipe, and the rubber 

 tubes were treated in different ways. One section of each specimen was roughened; 

 a second section was wrapped in burlap; a third section was taped with plastic; a 

 fourth section was taped with rubber electrical tape; and a fifth section was left 

 smooth. The various wrappings were to provide a favorable foothold for the attach- 

 ment and growth of deep sea fouling and boring organisms. A large piece of 

 untreated fir was fitted around both unwrapped ends of each specimen to attract and 

 lead the borers into direct contact with each plastic specimen. 



Four different kinds of rope, made of synthetic plastic fiber (nylon and poly- 

 propylene) and of natural fiber (cotton and manila), were placed on the bio-racks. 

 Electrical cables covered with rubber or plastic insulation of various thicknesses 

 were also placed on the racks. A small piece of pine was fitted around each cable 

 specimen to act as bait for marine borers. Another group of electrical conductors 

 placed on the bio-racks consisted of No. 16 tin-coated copper wire with 0.015-inch- 

 thick insulation. The materials used in the formulation of the insulation are presented 

 In Table 3. The wire specimens were 15 Inches long, and both ends of each specimen 

 were sealed with two coats of silicone rubber cement. The rope and conductor 

 specimens were positioned so that one set of each would be burled in the sediment 

 (in which bacteria are ordinarily most active) and identical sets would be exposed 

 about 3 feet above the sediment. 



In addition to the materials placed in the bio-racks, test specimens were also 

 placed inside a sterile plastic test chamber which was secured to the side of the 

 STU about 4 feet above the mud line (Figure 5). The test chamber consisted of 

 5-inch-diameter (OD) by 24-inch-long acrylic tube, both ends of which were cov- 

 ered with 0.45-micron membrane filters to keep out marine bacteria. Before 

 submergence, the materials placed inside the tube were sterilized with ethylene 

 oxide gas. Identical materials were also placed outside the test chamber and exposed 

 to the natural sea environment. This test was initiated to determine the role played 

 by marine microorganisms in the deterioration of cotton and manila ropes and corro- 

 sion of metallic specimens. Materials placed in the bio-racks and in the plastic 

 test chamber are listed in the Appendix. 



Metal test specimens were also placed on the STU, but materials containing 

 antifouling paints or other toxic substances were excluded. The velocity of the 

 current at a depth of 2,370 feet (about 0.06 knot) was not great enough to carry 

 away any water-soluble toxic substance which might change the behavior of the 

 natural biological fauna found in the immediate vicinity of the STU. 



