fishery resources led to extensive surveys of spatial and temporal 

 variations of these nutrients. Gross inventories have been defined on 

 a world basis and gross rates of reaction rates have been measured, 

 especially in favorably hydrographic situations where information about 

 physical movement and mixing of water masses has been available. 

 Global estimates of primary productivity have also been accomplished. 



Recent mathematical modeling of microscopic processes coupled 

 with careful experimentation at natural (low) levels of chemical con- 

 stituents have produced unexpected and useful results (Droop, 1968; 

 Sieburth, 1969; Button, 1971, 1972; Caperon and Meyer, 1972a,b; 

 Thomas and Dodson, 1972). Instead of growth rates being simply 

 related to water composition, such systems are quantitatively described 

 by transport relations describing the simultaneous flux of several nutri- 

 ents to the cell surface (up concentration gradients of 10^ — 10^ by 

 active transport mechanisms), back-diffusion relations of nutrients 

 and organic waste products, and internal nutrient regulation of growth 

 through kinetic enzyme relations, (Button, 1972). These models are 

 fairly simple and can be handled by computer techniques. Network 

 models of such systems are feasible. Such models should be used to 

 guide the design of laboratory and field experiments. 



Some early results may serve as an example of the type of guidance 

 that can be expected. The low controlling levels of chemical constituents 

 and the competitive nature of the membrane transport sites imply that 

 very low concentrations of nutrients (and of antimetabolites such as 

 arsenate, trace metals, etc.) must be considered simultaneously. Rates 

 of backleakage of nutrients and of organic metabolites significantly 

 aff"ect water chemistry as well as the flux relations in the models. Diff'er- 

 ences in continuous and batch incubation results should be examined 

 in regard to field methods. The models and their results should also be 

 examined as aids in the design of experiments on the eff'ects of pollution. 



Nutrients and Dissolved Gases— T\iQ abundances of the nutrient 

 salts, phosphate, silicate, nitrate, nitrite and ammonia, plays a major 

 role in controlling the productivity of the sea. Previous research has 

 been focused on the development of suitable analytical methods and 

 the application of these methods to the definition of the temporal and 

 spatial distribution of nutrients in the ocean. Much of this definition 

 has been accomplished, and it is now time to focus research on the 

 rates and regulation of those processes that control and determine the 

 characteristics of the nutrient fields, to construct mathematical expres- 

 sions to describe these processes, and to nest these expressions in a 

 predictive mathematical model. The mathematical model cannot be 

 constructed or verified from our present knowledge of the rates and 

 regulation of these processes, and since this inadequate understanding 



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