The crushing strength of a 2-1/2-Inch by 3-1/2-Inch by 4-1/2-Inch concrete 

 specimen was 1, 726 pounds per square Inch. It Is suggested ° that a good concrete 

 containing aggregates of gravel and broken stones would offer greater resistance to 

 attack by these rock-boring animals. 



Marble columns which were part of the cargo of a Roman ship wrecked In the 

 Mediterranean Sea in the first century B. C. were found riddled by the rock-boring 

 animals Lithophaga and Pholas , producing a spongy appearance. 



Fiber mooring ropes which held buoys and mooring floats to anchors were 

 damaged by Teredo morsel Bartsch, and some ropes were entirely severed mainly at 

 the lower ends (near the attachments to the anchors). 



Marine Bacteria 



The marine bacteria's indispensible function In the biological cycle of the sea 

 is primarily one concerned with transformation of organic and Inorganic substances. 

 The characteristics, distribution, and function of marine bacteria have been described 

 in great detail by ZoBell. '^ Some are autotrophic bacteria and are able to build 

 carbohydrate and protein out of simple substances such as carbon dioxide and 

 inorganic salts. One group of autotrophes, the chemosynthetic bacteria, derive 

 their energy from the oxidation of various Inorganic compounds such as hydrogen 

 sulfide, sulfur, or ammonia on the sea bottom where there is insufficient light for 

 photosynthesis. However, the majority of marine bacteria are heterotrophic bacteria 

 which obtain their energy and carbon source by the oxidation of organic compounds. 

 During bacterial metabolism the organic substances in the sea water and sediments 

 are transformed Into carbon dioxide, water, ammonia, and minerals. These bacteria 

 convert from 30 to 40 percent of the carbon of organic compounds into bacterial 

 cell substances. ' ' Other geochemlcal changes which take place during the bacterial 

 metabolism include consumption of oxygen, production of heat and hydrogen sulfide, 

 and changes in hydrogen-Ion concentration. 



Marine bacteria are found In sea water and In bottom sediments from shallow 

 depths to the deepest portion of the sea. The greatest number have been found in 

 coastal waters where the greatest abundance of plant and animal life is also produced; 

 however, the greatest density by far of bacterial population is found on the bottom, 

 where millions of cells per gram of wet mud may occur. '■^ The aerobic bacteria, 

 which require free oxygen for growth, are found in sea water and In the first few 

 inches of bottom sediment. The anaerobic bacteria, which are able to grow in an 

 environment where free oxygen is absent, are usually found in areas where relatively 

 heavy accumulations of organic matters are found, such as In marine bottom sediments, 

 under deteriorating organic coatings of various materials, and in minute pits found in 

 corroding metal surfaces. 



