their causative and diagnostic potentials and can be identified as impor- 

 tant research areas. The commonly recognized water mass characteris- 

 tics, such as the original temperature-salinity relationships among the 

 conservative and nonconservative properties such as O2, alkalinity, 

 pH, silicate, etc., will continue to be useful water mass tracers. However, 

 many other biologically imparted characteristics can be used to give us 

 more detailed knowledge of fields of motion and, perhaps even more 

 importantly, of the fate and eff'ects of biologically active substances in 

 the ocean — whether they be naturally produced or artifically introduced. 



Water mass properties that may be important both in describing fields 

 of motion and in predicting oceanographic environments are listed below 



1. Departures in the ratios of the major constituents resulting from 

 alkaline-earth uptake, sulfate reduction, and similar processes 

 2. Trace-element concentrations and the ratios of the various ionic and 

 molecular species in which the trace elements occur 



3. The ratios of biologically altered nutrient substances, e.g. C:N, 

 N:P, P:Si, and the concentrations of particulate and organic carbon 



4. The presence of biologically active materials probably will be 

 detected in the immediate future by bioassays. It is evident that these 

 substances, along with toxic materials, have important consequences. 



5. Petroleum and the identification of petroleum fractions might give 

 important clues as to the origin of water masses and their course through 

 the oceans. Persistent synthetic chemicals may prove useful as tracers. 



6. The use of dissolved O2 as a water mass tracer is historical and 

 well documented. In specific areas where nitrogen fixation or denitri- 

 fication alters the nitrogen content, precisely determined N2/Ar ratios 

 should be useful tracers. 



7. Alkalinity and pH have been shown to be useful in tracing upwell- 

 ing waters, estuarine waters, and in evaluating biological changes in 

 such waters. 



8. Man-made radioactive isotopes were the first artificially introduced 

 water mass tracers useful over wide oceanic areas. Changes in the 

 ratios of stable isotopes concurrent with biological processes could 

 also be useful in this connection. 



The growth and composition of plankton and micro-organism popula- 

 tions are subject to chemical controls. In turn, these biological processes 

 significantly alter the chemistry of the water through both obvious and 

 subtle feedback mechanisms. Indeed, the two biological processes of 

 primary production and microbiological degradation are fundamental 

 to the chemistry of the sea by displacing the equilibrium of the system 

 and by catalyzing reactions back toward equilibrium. 



Early realization of the importance of nutrients (P, N, and Si) to 

 primary production and the hope of a fairly direct link to locations of 



56 



