BIOLOGICAL OCEANOGRAPHY 



Deterioration of submerged installations by marine organisms 

 is another serious threat to present and proposed marine operations. 

 Extensive destruction is caused by species of Limnoria, or gribbles. 

 These animals are related to the shrimp and lobster and are worldwide 

 in distribution. They are normally found attacking the .surface of 

 submerged piling and other wooden structures in shallow water, but 

 materials other than wood, such as the gutta-percha insulation of 

 submarine cables in depths up to 360 feet, have been penetrated by 

 gribbles. Other crustaceans burrow into, and consequently weaken, 

 stone seawalls. 



Certain mollusks, such as the well known teredo, or "shipworm", 

 relatives of the clam and oyster, attack submerged wooden structures 

 in harbors, or burrow into rocks and coral. Mollusks are also respon- 

 sible for destructive attacks on gutta-percha insulation of cables at 

 depths ranging from a few feet to 7,200 feet, causing physical damage 

 and short circuits. Others have been found to penetrate solid lead 

 sheathing of submarine power cables. Even concrete is not immune 

 to destructive attacks by these creatures. 



Kock-bonng btuahes, worms and sponges attack hard iimcstonc. 



Marine bacteria play a surprisingly important role in the deter- 

 ioration and fouling of materials and equipment in sea water and 

 marine sediments. These micro-organisms accomplish their destruction 

 in a number of ways. By forming over antifouling agents, to which 

 they are apparently immune, they provide a foothold for barnacles 

 and other fouling animals. Cellulose-decomposing bacteria cause 

 millions of dollars worth of damage to net cordage, seines, and lines 

 used by commercial fishermen. Also present in the sea are cellulose- 

 consuming fungi which infest natural fibers and woods. Rubber prod- 

 ucts such as hoses or gaskets, generally regarded as being impregnable, 

 have been found to be decomposed by the action of marine bacteria. 

 Sulfate reducing bacteria have been associated with the accelerated 

 corrosion of submerged metals. Here again, the problem of protecting 

 deeply submerged materials from the ravages of these organisms is 

 complicated by the fact that some bacteria actually thrive in deeper 

 water, reproducing only when subject to great pressures. 



Even the color of materials used in underwater installations has 

 an influence on the attacks by marine fish. Attracted by its white 

 color, the polyethylene insulation of marine cables has been extensively 

 damaged by the nibbling of certain fishes. Biologists have suggested 

 a less attractive insulation color to reduce such attacks. 



The fouling and destructive potential of a segment of the sea's 

 population is, thus, clearly illustrated and defines present and future 

 requirements for more effective control. To meet the requirements 

 our understanding of the vital processes which govern the life cycles 

 and behavior of the offending organisms must be broadened. Ade- 

 quate knowledge of such processes should lead to the discovery of an 

 inherent weakness in each organism which is susceptible to external 

 control. 



BIOLUMINESCENCE 



A biological phenomenon well known to mariners is the relatively 

 common yet curious sight of luminescence in the sea. At first believed 

 to be caused by the presence of the element phosphorus within the 

 water, it has been known for almost two centuries that the phenom- 

 enon is biologically induced. In its most familiar form, luminescence 

 is observed as a bluish-green fluorescent glow in waters disturbed 

 by bow waves and wakes, and by cresting waves. Luminescent dis- 

 plays occasionally attain more spectacular proportions, however, 

 forming parallel bars, or "wheel spokes", of pulsating light extending 

 from horizon to horizon. Sometimes the wheel spokes appear to rotate 

 like a giant pinwheel. 



A simplified version of the occurrence is that tiny plants and 

 animals, some even microscopic, exist in the near-surface regions of 

 the sea in countless numbers and react to various stimuli by emitting 

 light. The light emitting properties of many of these organisms permit 

 them to alternate, or flash, their light in a manner similar to the 

 common firefly. The rhythm of flashing depends in most cases upon 

 the kind of stimulation introduced. Some of the lowly dinoflagellata, 

 a group of single-celled organisms strangely cast on the borderline 

 between plants and animals, are known to possess this characteristic. 

 Since they abound in the upper portions of the oceans, dinoflagellata 

 are among the better known organisms responsible for the lumines- 

 cence observed by seafarers. 



Because they often exist in huge concentrations, luminescent 

 organisms are capable of producing an amazing amount of light. 

 In certain geographic regions, agitation of the sea by the passage of 

 a vessel at night produces enough illumination on deck to enable one 

 to read. When the stimulation is passed through them in waves, 

 their rhythmic reaction may give the impression of a symmetrical swirl- 

 ing movement of light, thus creating the pinwheel illusion. The 

 parallel bar effect occasionally observed is accounted for by the move- 

 ment of the sea, which even under calm conditions, circulates 

 vertically in such a way as to concentrate the organisms in horizontal 

 streaks. 



While surface displays are the most frequently observed, bio- 

 luminescence is not confined to the upper regions of the sea. Light 

 producing organisms have been found to exist at every depth. In 

 the blackness of the abyssal depths, where sunlight never penetrates, 

 the light produced by certain animals provides almost constant 

 illumination, to the mutual benefit of themselves and others not so 

 equipped. The fact that the latter creatures have well-developed 

 eyes, and are obviously dependent upon alien sources of light, is 

 evident of the close interrelation of these deep dwelling species. To 

 fully understand the significance of luminescence in the ecology of 

 marine life is a constantly expanding project for oceanographers. 



Vtdcanized insulation of submarine cable slashed by shark 

 who left some imbedded teeth as evidence. 



A 6" slomiatoid fish taken in net tow at 2,000 feet (a-ppr ox.) 



To the casual observer, luminosity of sea water is but a harmless 

 manifestation of natural wonder. In the conduct of naval operations, 

 however, the phenomenon is viewed with a jaundiced eye. Observed 

 from the air, or from the bridge of a large vessel, the luminous wake 

 of a ship travelling at even moderate speeds can be detected for some 

 distance, clearly revealing its position and, roughly, its direction 

 and speed. During World War II amphibious landings and other 

 naval movements were, on several occasions, compromised by the 

 presence of bioluminescence. Consequently, another goal of the 

 oceanographer is to eventually establish a pattern of reoccurrence so 

 as to forecast the periods of luminescence in areas of projected naval 

 operations. 



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