The Composition, Especially the Hydrogen Ion Concentration, of Sea Water in Relation to Marine Organisms

Since the extensive analyses of Forchhammer and Dittmar, the relative concentration of the chief salts in sea water has been accurately known, the differences in the results of different investigators only slightly exceeding the differences in the values of the atomic weights that they used. Omitting regions affected by land drainage and the melting of the polar ice caps, ocean surface salinity (gm. of total salts per kilo) varies only from about 33 to 38, the most dilute region being the North Pacific. The known ocean currents affect only the surface layers, but there is probably a drift of the bottom water chiefly from the South and less from the North Polar regions toward the equator, which could take place at a depth of 4,000 meters without obstruction. The evidence for this is the fact that the depths of the oceans have a remarkably uniform salinity of nearly 35 and temperature of about 2” which is much above the temperature of maximum density, and are fairly well oxygenated. It seems safe to infer, therefore, that all surface water has comparatively recently come from the depths under the equator. Dittmar showed that there is proportionately0.44 per cent more CaC03 at the bottom than at the surface, due to the solution of pelagic shells by means of the COZ from organic decomposition. It is evident, therefore, that the CaC03 brought from the depths and from the land is precipitated in surface water, especially in the tropics. Drew supposes that this is not done entirely by the formation of shells and skeletons, but also by the action of denitrifying bacteria which increases the alkalinity of the water by removal of nitrates until the solubility product for CaC03 is exceeded. Palitzsch has shown that the alkalinity of the sea varies inversely with the depth, but this is probably largely the result of changes in CO, content due to the synthesis of organic matter at the surface and its decomposition in the depths, and less to the changes in nitrates, especially since nitrates and ammonia vary in the same direction. The effect of denitrifying bacteria is probably greatest where the sea is diluted with fresh water. I