from the within- station variability. With 

 the aberrant sample discarded, we have a 

 grand mean of 292 cpm. with a standard devia- 

 tion of 52.8 cpm. 



There is then, no evidence of heterogeneity 

 among the nine stations. Any single sample 

 should give a fair estimate of the productiv- 

 ity of this 6 mile square area, with, however, 

 a standard error of 52.8 cpm. which is l8°/ 

 Of the mean value encountered. 



Chlorophyll "a" was determined from a single 

 6 liter surface sample at each station. The 

 results are given in Table 5. 



Since we have only a single chlorophyll sample 

 from each station, we cannot examine the ques- 

 tion of heterogeneity of this constituent among 

 stations. The degree to which any single sam- 

 ple may be expected to represent the mean 

 value within the area may, however, be Judged 

 from the standard deviation among the nine 

 samples of O.OhQ mg/m^, which is 12°/ of the 

 mean value. 



Superimposed upon sampling variability, of 

 course, would be that due to the inherent 

 diurnal periodicity in photosynthesis and 

 chlorophyll (see p. 82). However, such a 

 periodicity is not evident in these particular 

 data. 



SURFACE CHLOROPHYLL "a" ZOOPLANKTON VOLUME 

 RELATIONSHIPS 



In figure h surface chlorophyll "a" and zoo- 

 plankton volume data obtained on both SCOPE 

 and EASTROPIC are illustrated. While there is 

 some scatter, the observations reveal that a 

 positive relationship exists between these 

 two quantities. The correlation might have 

 been improved had we a sufficient number of 

 vertical chlorophyll "a" profiles for inte- 

 gration and comparison with the zooplankton 

 volumes . 



Similar data from mid to high northern and 

 high southern latitudes have frequently 

 shown an inverse correlation, or none at 

 all. The lack of extreme variation in this 



relationship indicates that there may exist 

 in these tropical waters a situation more 

 closely approaching a steady state condition 

 than is found in other waters. Furthermore, 

 the general agreement among surface chloro- 

 phyll "a", surface productivity, and zooplank- 

 ton volume shows that any one of these will 

 serve to indicate the general level of the 

 other two. 



PRODUCTIVITY PER UNIT CHLOROPHYLL "a" IN SUR- 

 FACE PHYTOPLANKTON 



The relationship between photosynthesis and 

 chlorophyll "a" concentration has been 

 studied and discussed by a number of investi- 

 gators - see for instance Glendenning et al. 

 (1956), Rabinowitch (1956), Ryther (l955)~ 

 Few of these observations include data for 

 marine phytoplankton species, but it is of 

 interest to note that for those studied the 

 ratios are quite similar to those observed in 

 some land plants and algae. 



The SCOPE data available for this comparison 

 are of two types: a) the photosynthetic 

 rate obtained with surface samples inoculated 

 with C 14 ' and incubated for four hours under 

 constant light (1000 ±. ItO foot-candles) at 

 approximately the temperature of the sea 

 surface, and b) the rate based on C ll+ inoculat- 

 ed samples trailed astern of the vessel at the 

 surface for about six hours (sunrise to noon, 

 and noon to sunset). Chlorophyll "a" deter- 

 minations were made with water samples col- 

 lected at, or nearly at the same time, as 

 the samples for the photosynthesis studies. 



lit- 

 The amount of C fixed per hour at 1000 foot- 



candles in surface water samples is presented 

 as a function of surface chlorophyll "a" concen- 

 tration at each station in figure 5. While 

 there is considerable scatter, the data appear 

 to fall into two discrete clusters. Best-fit 

 lines "drawn" by eye through these two groups 

 yield the following rates: 7.3 and 2.5 mg 

 C/hr/mg chlorophyll "a", or, 26.8 and 9.2 mg 

 C0 2 /hr/mg chlorophyll "a", respectively. 

 Ryther and Gertsch (1957) give an average 

 value of 3.7 mg C/hr/mg chlorophyll "a" for 

 natural populations at 1500 foot candles. This 



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