NUTRIENT BUDGETS 303 



important. If a steady state be assumed and if the values for contribu- 

 tion and loss are reasonably accurate, then the difference, which may be 

 attributed to denitrification, amounts to 70 x 10® tons annually. This 

 is only five-millionths of the molecular nitrogen dissolved in the oceans. 

 The circulation of ocean water is undoubtedly sufficiently rapid to pre- 

 vent supersaturation at depth even with this magnitude of denitrification. 



Bacterial denitrification is an anaerobic process and consequently it 

 should occur only in inshore sediments. Unless anaerobic micro-environ- 

 ments can exist in the water column or unless chemical denitrification 

 takes place in the sea, then no more and probably considerably less than 

 8.6 X 10*^ tons of molecular nitrogen should be formed annually: a quan- 

 tity equal to the nitrogen returned to the water from the sediment. Tak- 

 ing the lower value for denitrification, the annual loss of nitrogen is 

 considerably less than the calculated contribution by rivers and rain. 

 If steady state conditions exist, one or more of the estimates must be in 

 error and, considering the meager data available, our estimates for the 

 nitrogen content of rain water over the ocean and those for ammonia and 

 organic nitrogen content of river water are all subject to question. 



PHOSPHORUS 



An average concentration of 2.4 jug-a/L throughout the whole vol- 

 ume of the ocean, derived from the phosphate-depth curves of the oceans 

 (Sverdrup, Johnson, and Fleming, 1942, p. 241), yields a total of 1.1 

 X 10^^ tons of phosphorus. To this must be added phosphorus in dis- 

 solved organic matter. From the data of Redfield, Smith, and Ketchum 

 (1937) it appears probable that phosphorus in dissolved organic matter 

 of near-surface waters is about 7% of the phosphate-phosphorus. Pre- 

 liminary studies by E. D. Goldberg (personal communication) suggest 

 that approximately the same ratio may also be valid for deep waters. On 

 the basis of this ratio, there are 0.1 x 10^^ tons of organic phosphorus in 

 the oceans, making a total of 1.2 x 10^^ tons of all phosphorus dissolved 

 in the ocean water (Table 1). 



Annual use of phosphorus amounts to 1.3 x 10^ tons as computed 

 from the compromise of 150 grams carbon per square meter annual 

 assimilation and a weight ratio of 0.024 for phosphorus to carbon in 

 plankton (Sverdrup, Johnson, and Fleming, 1942, p. 929). The ratio 

 of annual use to oceanic reserve is 1%, the same as for nitrogen, and it 

 is again doubtful that circulation is rapid enough to bring 1% of the 

 water within the photosynthetic zone for extraction of phosphorus by 

 phytoplankton. 



