Test Site II was selected because the area provides a nominal 2,500-foot depth 

 reasonably representative of the open-sea conditions in the eastern part of the 

 Pacific Ocean. It is located about 75 nautical miles west of Port Hueneme, 

 California. 



In addition, a depth of about 2,500 feet was selected because the dissolved 

 oxygen content in seawater fails to a relatively low value. This depth is known as 

 "the minimum oxygen zone." Below and above this depth, the dissolved oxygen 

 content increases. The underlying causes of "the minimum oxygen zone" are still 

 imperfectly understood. 



Because the rates of corrosion of certain metals and alloys are greatly influ- 

 enced by the concentration of dissolved oxygen in seawater, it was desired to 

 investigate the effects of the minimum oxygen zone on materials. 



Biological Activity 



Rock Samples. Rock specimens were desired from this area in order to enable 

 study of any fouling organisms attached to the rocks. Such animals could be expected 

 to attach themselves to test specimens placed there. Before placing the STU at this 

 test site, a dredge, made of 10-inch-diameter by 36-inch-long steel pipe with 

 retaining rods welded across the lower end of the pipe, was lowered to the ocean 

 floor from the oceanographic vessel, USNS Davis (AGOR-5), and the area was 

 dredged for rock specimens. Several passes were made across the area, but no 

 specimen was found. 



Sediment Samples. Marine bacteria are among the major biological agents in 

 the deterioration and fouling of various materials submerged in the sea. To determine 

 the type and activity of bacteria found In the deep sea, sediment samples were obtained 

 from the ocean bottom and analyzed in the laboratory by means of standard micro- 

 biological methods. The types of bottom samplers used, the media used to grow the 

 microorganisms, and the result of bacteriological analysis of the sediment samples 

 are presented In Reference 3. 



Some of the sediment samples which were obtained from this site were washed 

 through a screen to collect mud-dwelling organisms; those found were bottled and 

 preserved in a 5% glycerol-alcohol solution for laboratory analysis. Amphipods, 

 polychaete worms, and brittle stars were the most abundant marine organisms collected 

 in the vicinity of Test Site II. 



Test Materials . For evaluating deep sea biological effects on nonmetallic 

 specimens, two bio-racks (Figure 3) were attached to the STU. Each rack held several 

 3-foot-long plastic rods and tubes and a 12x30x l/8-inch laminated phenolic plastic 

 sheet. Numerous smaller test specimens, including wood specimens, were attached to 

 the plastic sheets; one sheet was secured to the upper section of one bio-rack, and 

 an identical sheet was secured to the bottom section of the other. In order to expose 

 the test materials to biodeterloration in mud as well as in water, the two racks were 



