38 



Papers from the Department of Marine Biology. 



air is therefore the average CC>2 tension of the sea-surface. The burn- 

 ing of a billion tons of coal per year is probably changing the CO 2 

 content of the sea and of rocks and not of the atmosphere. 



Regnard kept a tall open tube filled with a solution that became 

 colored in the presence of oxygen at constant temperature to prevent 

 convection currents. At the end of one year oxygen had diffused 4 

 meters deep into the solution. Although some oxygen was used in 

 coloring the indicator, the experiment illustrates the slowness of diffu- 

 sion in liquids. 



Since both the conversion table for C02 content and the one for 

 COa tension are based on the assumption that the non-volatile buffer 

 and the excess base in sea-water are constant, further work is being 

 done on this subject. It seems probable that the weak bases in sea- 

 water may assist the buffer action. The concentration of NH 3 is 

 small, but is added to the total buffer value ; it is non-volatile under the 

 conditions present at the surface of the sea and is constantly being 

 replenished by rain as it is used by organisms. Aluminium can act both 

 as weak base and weak acid, but probably acts as a weak base in the sea. 

 Organic acids besides C02 may be classed as non-volatile buffers. 

 Their destruction in warm seas is probably due to the action of 

 denitrifying bacteria, which catalyze the oxidation of organic matter 

 with nitric and nitrous acids, as shown by Drew. The concentration of 

 organic acids is probably maintained just below that which can be 

 appreciably utilized by these bacteria. 



The following artificial sea-water was found excellent for the growth 

 of marine Protista and experiments in places where sea-water can not 

 be obtained (the volumes being correct for 20) : 



If Na^SiOs is used, it should be dissolved hi the H 2 O before adding 

 the other salts or it will be impossible to get into solution. We used 

 a thick sirupy solution of water-glass (said to be Na^SLjOg) and made 

 an analysis of the Si concentration because we wished to ascertain the 

 buffer value, but for the growth of organisms it is sufficient to consider 

 the commercial solution as equivalent to 6 m Si0 2 or 1.5 m Na 2 Si40 9 , 

 and the quantity desired should be obtained by successive dilutions, 

 as a strong solution will precipitate when added to the other salts. 



