Chapter II — 23 — The Marine Environment 



and have formed extensive fossil deposits known as diatomaceous earth. 

 Several hundred species of marine plankton diatoms have been described 

 by Cupp (1943) who lists much of the relevant literature. 



Outstanding in importance among the higher plants is eel grass, Zos- 

 tera marina, an angiosperm which is widely distributed along the protected 

 coasts of Asia Minor, eastern Asia, Europe, and North America. Phyllo- 

 spadix, a related genus, is confined to the open, wave-washed coasts of 

 the Pacific. Six genera of Potamogetonaceae closely related to fresh- 

 water Potamogeton species also inhabit the sea. In all there are only 

 around 30 species of marine Spermatophytes (seed plants) and no known 

 Pteridophytes (ferns) or Bryophytes (mosses). Besides providing food 

 for animals and saprophytic microorganisms, aquatic Spermatophytes, 

 algae, and certain diatoms provide anchorage for sessile microorganisms 

 of various kinds including bacteria. The interrelationships of bacteria 

 and plants are outlined in Chapter XIV. 



Vegetation is described by Coker (1938) as "the broad base of the 

 pyramid of life in the sea. The contrast to conditions on land is marked. 

 None of the higher plants occur in the ocean remote from the shores. The 

 great group of blue-green algae, abundant in lakes and rivers, are promi- 

 nent in the ocean only in the waters near the mouths of large rivers or in 

 tropical regions. The green algae, predominant in fresh waters, are 

 sparsely represented in salt water and then chiefly where there is some 

 admixture of fresh water. The off-shore plant life, barring the floating 

 Sargassum, is of extreme simplicity of form. Even the relatively simple 

 filamentous forms, so characteristic of all sorts of fresh water, are missing. 

 Conditions in the sea have not favored cell aggregations and the associated 

 specialization in form and development of larger bodies. . . . The basis of 

 all the life in the modern ocean is to be sought in the microorganisms of 

 the surface." 



In comparing animal life in the sea with terrestrial and fresh-water 

 faunas, Coker (1938) points out that "the diversity in basic types of 

 living animals is much greater in the ocean than in fresh water or on 

 land. . . . There is in the ocean a predominance of the more primitive types 

 of animals and of those types that constitute the possible links between 

 the several phyla. In a way we may look upon the seas as representing a 

 living museum of biological antiquities, or it might better be said, as com- 

 prising the chief repository of the early archives of our family history." 

 This may also be said of the bacterial kingdom which is represented in the 

 sea by a great diversity of species, including many primitive forms. 



The animal population of the sea has far-reaching effects on the marine 

 environment and the microbial population. Some of the factors influ- 

 encing the distribution of animals in the sea are discussed by Ekman 

 (1935). The sea is the home of over 60,000 species of mollusks, about 

 half as many crustaceans, 15,000 fishes, and enough representatives of 

 other classes to make a total of around 150,000 species of marine animals 

 which have been described. Of the 48 major classes of animals only in- 

 sects, reptiles, birds, myriopods, amphibia, and mammals are predomi- 

 nantly non-marine. Most of the other classes are predominantly or al- 

 most exclusively marine. In the latter category are coelenterates, cteno- 

 phores, echinoderms, sponges, tunicates, and bryozoans, all of which are 

 largely confined to the sea. 



Of special microbiologic and oceanographic interest are the Protozoa, 

 of which there are many thigmotropic and planktonic types. In the 



