Abstract
The geochemical balance and cycles of P, Si and N in the oceans are discussed taking the following items into consideration: concentration in sea water of each nutrient matter in oxidative, preformed and organic form, input from rivers, biological production and decomposition, deposition to the sea bottom and transfer between the surface and deep layers.
Results show that the remarkable difference in concentrations in nutrient matters between the Pacific-Indian and the Atlantic Ocean is mainly due to difference in the residence time of waters in deep layer in each ocean.
The residence time of deep water which is estimated on the basis of the geochemical cycles of nutrient matters is 160-270 y and 90-130 y respectively for the Pacific-Indian and the Atlantic.
To compare the biological activities on nutrient matter, a new concept, Biological Activity Index, β is introduced.
