Factors affecting productivity in fertilized salt water 463 



populations is complicated by the existence of many phenomena which do not operate 

 in one-phase, single-species cultures, and which may be exceedingly dillicult to 

 dupUcate in ordinary laboratory conditions. While the large outdoor tanks do not 

 provide the elegance of complete environmental control available in the laboratory, 

 they permit some control, as well as a degree of simplification not available in natural 

 shallow habitats, in which the mud-water interface makes complications. They proved 

 to be very useful in providing a large, manipulable environment, intermediate between 

 laboratory cultures and natural bodies of water, from which large samples could be 

 withdrawn without seriously depleting the population. They may profitably be used 

 in the problem of interpreting natural situations, and in designing etlicient programs 

 of experiments with controlled conditions. 



One of the pressing problems is to establish relationships among the various popu- 

 lation functions which are involved in biological production. Of these, the relation 

 of photosynthetic rate to amount of chlorophyll present, and the degree to which 

 this relation may be modified by various environmental conditions, has been dis- 

 cussed at length. The ecological position of chlorophyll is obvious, but critical 

 studies must be continued before much useful prediction from measurements of 

 chlorophyll can be made. A second problem of interest is that of the interrelations 

 Bmong photosynthesis, population growth, and nutrient uptake. It must be expected 

 that in general these functions will be related, and measurements of one will give 

 information about others which may in some situations not be measurable directly. 

 Finally, further development of methods of evaluating the extent to which various 

 factors are limiting production at any moment should lead to greater understanding 

 of the general problem of productivity. 



REFERENCES 



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Edmondson, W. T. (in press), The relation of photosynthesis by phytoplankion to light in lakes. 



EmerIw,'r., Green, L. and Webb, J. L. (1940), Relation between quantity of chlorophyll and capac- 

 ity for photosynthesis. P/ow? P/i>'.y/o/., 15, 311-317. f „l,„,„cv.r,th«.c 

 Fleischer, W. E. (1935), The relation between chlorophyll content and rate of photosynthesis. 



GAAS.?R,^Sd GiSn, hT H^(1927), Investigation of the production of plankton m the Oslo Fjord. 

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HUTCHINSON.G. E. (1941), Mechanism of intermediary metabolism in stratified lakes. Ecol. \fonogr., 



Je^^,'rV. (1937), Oxygen production by the diatom ^^f"'^^;^'^^^^^^^ '° 



KSS^t ^^i? Tlie ^^cSff c^SpHai ^L^a^e tn^^eJ^ui^t;^...... 



KE?cS; B. H.'(1939),^t' dl'd'pme'in and restoration of deficienceis in phosphorus and nitrogen 



Lr;^^^^^(y5S"s^c^s^n i;Sr^.^e'^i.!n'a:^ie of the cells producing 



seasonal maxima. -^^ -^^<'^-'. ^'^' ^^^"f '^^ .. r„^„,„^„ Hass II Nutrient depletion and the spring 



"rxiLl ''■i!^^?^^£^n:i::^^t/^:E:^^!^^^^^r and ei^lhan, Tarn J. W.. 



MA^^N^'w. M. and Jt;DAV, R. E. (1941), The chlorophyll content and productivity of sonK lakes 



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Nelson, P. R. and Edmondson, W. 1. (in press;, Liiiiiiuiugiv-a 



U.S. Fish and Wildlife Sery., Fish Bull. nho<;nhorus cycle in fertilized salt water. J. Mar. 



Pratt, D. M. (1950), Experimental study of the phosphorus cycie 



Res'., 9, 29-54. «„mptis D F (1949), Quantitative ecology of the plankton of the 



Riley G A., Stommel, H. and Bumpus, l^. r. i,i7t?y, vf !•> n^ t-l69 

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