Factors affecting productivity in fertilized 



salt water 



The following symbols will be used : 

 P Gross rate of photosynthesis, as mg/l/day of oxygen 

 Chlorophyll concentration, as i^gjl 

 Light at surface of tanks, cal/cm2/min of visible light 

 Light at mid-depth of tanks, same units 

 Phosphate concentration, /ng at/1 

 PIL 

 PIL' 



Rate of respiration of the population, mgm/1/day of oxygen 

 Net rate of photosynthesis, P-R 



457 



C 



L 



L' 



F 



P' 



P" 



R 



N 



lOO 



2^ 



2 

 < 



X 



o 

 o 



X 

 a. 



CHLOROPHYLL //qm/ 



Fig. 4. As in Fig. 3, but the values of light used are those at a depth of 50 cm in the water. The 



points marked by lines are for periods when diatoms made up less than half the photos>nthctii: 



population by volume. The insert at the upper left is a copy of Fleischer's Fig. 7 (sec text). 



The simple relationship between photosynthesis and chlorophyll (Fig. 2) is seen 

 to be rather low with a wide range of rate existing at all levels of chlorophyll con- 

 centration (rpc = 0-64). When each value of photosynthetic rate is divided by the 

 corresponding light income, the degree of scatter is considerably reduced (Fig. 3) 

 and the field of points is more nearly linear (r^.^^ ^^ 0-81). 



These coefficients show that, under the existing circumstances, a largo part o^ the 

 variation in photosynthesis is closely correlated with variations in but two factors 

 known to have influence, chlorophyll and light, and suggest that chlorophyll was 

 controlling more often than was light. 



To give the results in a more complete numerically descriptive form, several 

 hnear regression equations were calculated. Of particular use in these equations is 



