BIOLOGICAL OCEANOGRAPHY 



stinging coral 



Elkhorn coral 



Following World War II, a war fought in coral seas of which 

 little was known, a marked intensification of coral reef investigation 

 took place which has resulted in the acquisition of valuable biological 

 data. The importance of continued research lies not only in the fact 

 that the constantly growing reefs pose a serious threat to present 

 and future marine operations, but improved harbor maintenance and 

 the stabilization of many important islands may depend upon a better 

 knowledge of coral formation. The studies are also important in 

 expanding our knowledge of the general ecology of the sea, for as a reef 

 develops, other organisms become adapted to the environment, 

 thriving and contributing to a relatively "closed system" of existence. 



The most important builder on a coral reef is a creature very low 

 on the scale of evolution known as a polyp. These animals cement 

 themselves to an underwater platform and proceed to secrete an 

 external layer, or skeleton, of calcium carbon^ffi' which, due to the 

 shape of the young polyp, produces a stony limestone cup. As each 

 polyp matures it grows in size and complexity of structure, branching 

 and multiplying to eventually form large masses of dense rock. At 

 certain times of the year, the-polyps-reproduce their land by releasing 

 larva which are carried by the currents to other sites, where, if suitable 

 conditions of temperature and depth exist, a new reef is formed. It 

 has been estimated that billions of tons of rock are thus created each 

 year. 



Corals are specialized carnivores, subsisting on tiny planktonic 

 animals which they capture with their paralyzing tentacles. Typical 

 reef building corals characteristically contain within their tissues 

 numerous algae cells which they are incapable of expelling. This 

 symbiotic relationship between animal and plants contributes 



mutually to each other's well being, the exact significance of which 

 is the subject of considerable controversy among marine biologists. 

 It appears evident that the relationship is beneficial, at least to the 

 host polyp, for the most vigorous coral growth occurs within the 

 lighted depths, from 20 to 30 fathoms, apparently due to the fact 

 that the contained algae, like all plants, require light for survival. 



Coral growth is also dependent on other factors which include 

 favorable temperature, salinity, and nutrient value of the surrounding 

 water mass. 



A secondary but integral part of reef construction are the various 

 calcareous algae which grow upon the reef. In the course of time, 

 these stony plants have a mortise-like effect upon the environment 

 that binds the reef mass together, contributing to its over-all strength. 



Coral reefs are constantly subject to various forces that can 

 damage or weaken them. Erosion from the constant battering of the 

 sea can eventually cause massive breakage, and the deposition of 

 sediments on living coral beds results in eventual death of the beds. 

 A number of snails, worms, and barnacles bore deeply into the very 

 foundation of coral colonies. Naturally, a greater knowledge of the 

 effects of these forces is essential to present and future coral reef 

 studies. 



THE HARMFUL AND USEFUL ASPECT 

 OF MARINE LIFE 



Probably the most important problem that man associates with 

 survival at sea is the danger of attacks by obnoxious animals. Whether 

 this or other factors are the primary detriment to survival is debat- 

 able. The fact remains that sea life poses a serious threat to naval 

 operations involving swimmers and divers. Furthermore, as the 

 rapid advances in underwater equipment and techniques extend the 

 depth and range of such operations, there is a greater need for effective 

 deterrents against the threat. 



The number of species of marine animals capable of harming man 

 has been estimated at more than 3,000, and these are separable into 

 three categories — poisonous, venomous, and carnivorous. The last 

 category is undoubtedly the most familiar for it includes the biters 

 such as the fearsome shark. For a man-in-the-water the fear of sharks 

 is well founded, for out of approximately 250 species that inhabit 

 the seas, more than 50 are known to be dangerous. Furthermore, 

 sharks are to be found in all oceans from 45° north to 45° south 

 latitude. 



Because of the many attacks attributed to them, no other marine 

 animal has been more extensively observed than the shark. Over 

 the years, chemical repellent agents have been developed and used in 

 survival circumstances. Their effectiveness has been less than com- 

 plete, for incidents have been recorded in which sharks have demon- 

 strated unpredictably savage conduct in apparent disregard of the 

 repellents released. 



Attacks by other marine carnivores such as the barracuda and 

 the moray eel present a physical, as well as psychological hazard to 

 many types of underwater operations. Venomous animals, such as 

 the stone fishes, sea snakes, and numerous invertebrates, and a variety 

 of stinging organisms represent a constant menace to the survivor at 

 sea or the unwary swimmer or scuba diver. The development of 

 truly effective defenses against all of these forms will require far more 

 ecological and behavioral information than is now available. 



On the brighter side, however, there are good indications that 

 marine life itself can provide the answers to these and many other 

 problems. It has been observed that certain marine animals and 

 plants produce substances which either kill, repel, or confuse other 

 forms. By isolating and examining these substances, biologists hope 

 to discover more effective repellents or deterrents for use against 

 obnoxious animals. 



Studies of the pharmacological properties of marine plants and 

 animals may open the door on a new family of drugs. The defensive 

 poisons exuded by many sea organisms are believed to be the source of 

 potent new drugs for possible use in the war against cancer as well as 

 other human diseases. Anti-cancer drugs are also being sought in the 

 tissues of shark brains. 



Studies of the amazing swimming characteristics of certain 

 marine animals, such as the dolphin and seal, may provide information 

 useful in the design and construction of new hulls for surface ships 

 and submarines. Research on the swimming techniques of marine 

 animals indicates that many possess highly efficient propulsion 

 mechanisms, completely silent and accomplished without detectable 



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