BIOLOGICAL OCEANOGRAPHY 



Some obnoxioiis 



1. Moray eel. 2. Parrot fish. S. Sea bass, or grouper. 

 U. Barracuda. 5. Puffer. 



turbulence. This phenomenon is of considerable interest to the Navy 

 in the development of future submersibles. 



Biologists have determined that many kinds of marine animals 

 have the ability to detect and identify targets at great distances and 

 then swim toward them with unerring accuracy. Closely related to 

 this phenomenon is the ability of shoals of fish to perceive and respond 

 quickly to some sort of self induced signal. These signals suggest a 

 highly effective system of underwater communications. Research in 

 this field is expected to evolve new concepts of target detection and 

 identification, long range submerged navigation, and underwater 

 communications. 



Many other unique capabilities of marine organisms are being 

 studied in an effort to create new, and improve existing, man-made 

 devices. Biologists are investigating how marine animals such as 

 whales, porpoises, seals, and numerous fishes can sound rapidly to 

 great depths without developing the bends and other diseases con- 

 tracted by humans under similar conditions. The remarkable process 

 by which some marine animals can replace lost or damaged parts of 

 their bodies may hold secrets of cell formation useful to medical 

 sciences. The anti-bacterial activity of marine algae may aid in the 

 development of new antibiotics. The possibility of emulating natural 

 processes of air purification by constructing analogues based on the 



photosynthesis of algae is being investigated as a means of improving 

 submarine habitability. These are but a few of the potentially great 

 discoveries at hand, and, in every instance, success will depend upon 

 the systematic acquisition of fundamental biological data. 



FIELD METHODS 



A fundamental step in biological research is the collecting of 

 sample organisms for laboratory examination. In marine biology, 

 this step is complicated by the fact that the specimens must normally 

 be removed from a murky, three-dimensional medium, the sea. As 

 the objects of the search are, therefore, usually hidden from direct 

 view, they must be groped for in a manner vaguely comparable to 

 hunting for a button at the bottom of a well-stowed sea bag. The 

 search is, for the most part, dependent upon gear which can be lowered 

 to a desired depth from the deck of a ship. 



The size, mobility, and natural habitat of a sought-for organism 

 determines the type of sampling gear to be used. Traditionally, the 

 basic gear is the net, with a number of variations. The free swimming 

 animals are sampled with gear similar to the trawls used by commer- 

 cial fishermen. Bottom dwelling organisms are collected by dredges 

 and grabs. A dredge is simply a bag-like net attached to a heavy 

 framework which is dragged along the sea's floor. A grab consists of 

 a pair of heavy metal jaws, not unlike the construction workers' "clam 

 shell" shovel. Coring devices are used for collecting undisturbed 

 samples of bottom sediments. Because the microscopic nannoplankton, 

 such as the smaller diatoms, dinoflagellates, protozoans, and bacteria 

 pass through the finest nets, they must be collected in water samples 

 and then separated, usually by centrifuge, in a laboratory. 



In sampling the zooplankton, as required in studies of the deep 

 scattering layers, specially designed nets are towed through the 

 water at a predetermined depth. The depth is maintained constant 

 by a paravane-like device attached to either the tow wire or the net. 

 Accurate quantitative samples require that the amount of water 

 filtered be known, and this is dependent on mesh size, area of filtering 

 surface, shape of net, area of opening, and the speed of the towing 

 vessel. A more modern innovation of this technique employs a meter 

 at the net opening which registers the amount of water that enters 

 the net during a tow. Of course, some means must be provided to 

 open and close the sampling device at any desired time and depth. 



Because of their superior swimming ability, many of the larger 

 planktonic animals elude towed nets. Such losses can be reduced by 

 increasing the speed of the tow, but speed is limited by the strength of 

 available nets. To obviate many of the difficulties associated with 

 net tows samples have been collected by pumping them up, with 

 measurable quantities of water, through a hose from the required 

 depth and caught in filters aboard ship. A more recent variation of 

 this technique eliminates the hose and employs a submersible pump, 

 electrically controlled from deck, which is attached to a net and 

 lowered to a precise depth. A meter on the pump measures and 

 records the amount of water screened. 



A multiple plankton sampler. 



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