Chapter II — 21 — The Marine Environment 



strated that the activities of such microorganisms perceptibly influence 

 the dissolved nitrogen content of sea water (see Chapter XI). 



In surface water the dissolved nitrogen is in equilibrium with the at- 

 mosphere. The amount found at greater depths is believed to indicate 

 the temperature of the water when it occupied a position at the surface, 

 the solubility of nitrogen varying inversely with temperature. 



Artificial or synthetic sea water: — In experimental work it is often 

 desirable to work with artilicial or synthetic sea water. Since a solution 

 like sea water probably does not contain all the ingredients arbitrarily 

 combined, it is not surprising to find that several different formulae have 

 been proposed by different workers (Fowler and Allen, 1928; Sverdrup 

 et al., 1942). The formulae differ primarily in the form in which the con- 

 stituent ions are added and in inclusiveness. 



The formula for synthetic sea water given in Table V is based upon the 

 work of Lyman and Fleming (1940). It differs from their formula in that 

 it contains traces of certain additional constituents known to occur in sea 

 water which are essential for the growth of organisms. For convenience 

 in its preparation the amount of each ingredient is given on a weight to 

 volume basis. Synthetic sea water prepared according to this formula 

 has a chlorinity of about i9°/oo- After reaching equilibrium with the CO2 

 of the atmosphere the reaction is fti 8.0. With an appropriate source of 

 food or energy it provides for the growth of most marine diatoms, blue- 

 green algae, yeasts, molds, and bacteria which have been studied. 



Marine bottom deposits : — Environmental conditions on and in the 

 sea floor are of importance to the extensive benthic population. The lat- 

 ter consists of plants and animals to the depth penetrated by sunlight, 

 below which the benthos consists of animals, bacteria, and certain fungi. 



Animal and bacterial life has been recovered from bottom deposits 

 at all depths of water from which samples have been examined, but due 

 to technical difficulties of probing deep into the bottom deposits for suit- 

 able samples, it is not known to what depths within the bottom deposits 

 animals occur. Certain animals are known to penetrate near-shore bot- 

 tom deposits to a depth of two or three feet. However, penetrations to 

 such depths are usually temporary. It is doubtful if many animals live 

 in mud below the topmost few inches owing to the lack of oxygen. While 

 a few ciliates and other simple forms of animal life can live in an anaerobic 

 environment, most animals require oxygen. The lack of oxygen does not 



