6 MARINE PRODUCTS OF COMMERCE 



manufacture living substance. They use silica, lime, phosphoric acid, and strontia 

 to form their shells and skeletons, carbon dioxide and water to produce starches, 

 sugars, and fats, and nitrogen, sulfur, phosphorus, iron, iodine, etc. to make the 

 many complex chemicals characteristic of plants. 



These minute plants are almost inconceivably numerous and varied. Diatoms, 

 peridinians, brown and blue-green algae, and other microscopic forms of vege- 

 table and animal life, collectively called plankton, constitute the primary manu- 

 factiorers of food in the ocean. In the spring when the long hours of sunlight give 

 so much radiant energy to the surface of the North Atlantic, the concentration of 

 plankton is high enough to muddy the water. In the English Channel (Taylor, 

 1932) it has been estimated that 4,000 tons of vegetable matter are produced 

 annually per square mile. 



The minute plants are consumed by many different species of small animals, 

 such as snail-like mollusks, shrimplike Crustacea, globigerina, radiolarians, jelly 

 fish, and certain herring-like fish whose gills can strain the plankton out of the 

 water. In an investigation of the herring of the North Sea, Savage (1931) has 

 estimated that the herring which landed at the English east coast fishing ports 

 in 1926 required 109,000 tons of planktonic food. The herring family, including 

 herring, menhaden, shad, sardines, etc., and also mackerel, are consvimers of 

 plankton and, consequently, are important because they constitute a source of 

 plankton for the larger fish which cannot use it directly. 



Within the plankton population there is a continual struggle for survival against 

 the casualities due to parasitic infestations, bacterial depredations, and excessive 

 change of temperature. The dead and dying plankton tend to settle in enormous 

 numbers at the bottom of the ocean and become food for worms, mussels, scallops, 

 conchs, and other organisms which live there. These in turn become the food 

 of crabs, lobsters, cod, haddock, etc. It is thus evident that both on the surface 

 and at the bottom of the ocean the chain of life, via consumer and consumed, 

 tends to produce organisms large enough to be available to man. 



Even the vitamins of cod-liver oil can be traced to their ultimate source in 

 the oil of diatoms which grow and make oil in the sunshine at the surface of the 

 ocean. Ahmad (1930) obtained an oil, similar to cod-liver oil in its chemical and 

 nutritional characteristics, from a pure culture of the diatom, Nitzschia closterium. 

 Although little is known concerning the chemistry of plankton, enough is known 

 to show that the planktonic flora and fauna of the ocean collect and concentrate 

 many of the rarer chemical elements. The plankton organism Podocanelius makes 

 its skeleton of strontium compounds. Seaweeds and sponges have many times the 

 iodine content of sea water. Haber (1927) found more gold in plankton than 

 in the water. Oysters, which are plankton eaters, contain relatively large amounts 

 of copper, arsenic, manganese, iron, iodine, and numerous other elements. 



The ocean is an almost perfect nutrient solution, containing all of the elements 

 necessary for every form of life. Excluding insects, of which there are some 

 500,000 described species, about four-fifths of all other species of animals known 

 to man live there. Marine animals include more than 40,000 species of mollusks, 

 nearly as many Crustacea, and almost half this number of marine fishes. Of the 

 48 major classes of animals only insects, reptiles, birds, myriapods, amphibians, 

 and mammals are predominantly terrestrial. Several classes, including ctenophores, 

 porifera, coelenterates, echinoderms, and tunicates, are largely confined to the 



