SCOPE MEASUREMENTS OF PRODUCTIVITY, CHLOROPHYLL "a", AND 

 ZOOPLANKTON VOLUMES 



by 



R. W. Holmes, M. B. Schaefer, and B. M. Shimada 



The productivity, chlorophyll "a", and zooplank- 

 ton volume data obtained on SCOPE have not yet 

 been examined in detail. However, some aspects 

 of sampling variability, and certain of the more 

 obvious relationships among these quantities, 

 have been examined and are, in some instances, 

 compared with similar data and relationships 

 obtained in 1955 on Eastropic Expedition (Holmes, 

 Schaefer, and Shimada, 1957) • 



SAMPLING VARIABILITY 



Ik 



Measurements of C uptake and of chloropnyll 



"a" are subject to sampling variability due to 

 the nature of the distribution of phytoplankton 

 organisms in the sea. The question, therefore, 

 arises as to how representative of a general 

 area is a single sample taken from that area. 



In order to investigate sampling variability 

 over a relatively small area, as a first approach 

 to studying this problem, on November 22nd, 1956 

 in the vicinity of 09°25' N, 89*31' W, we 

 collected samples from a grid of nine stations 

 on a square pattern, the station spacing being 

 three miles. The station arrangement is shown 

 in Figure 3- These stations were visited in the 

 order shown, between 0915 and 1202. At each 

 station were taken three replicate surface 

 samples for the determination of C-^ uptake and 

 a single surface sample for the determination 

 Of chlorophyll "a". 



Ik 

 C uptake was determined in a 250-ml. aliquot 



of each replicate, using 0.9 ^C of C 1 ^, and 

 incubating each sample for four hours in the 

 shipboard incubator at the prevailing sea-sur- 

 face temperature, and at an illumination of 

 approximately 1000 foot-candles. The incubat- 

 ed samples were filtered through one-inch- 

 diameter HA Millipore filters, which were dried 

 in a desiccator and subsequently counted in a 

 proportional counter (Nuclear Chicago PC-1). 

 The counting time was of a duration to give a 

 total of at least 1000 counts in each instance, 



and varied from 6 to 10 minutes. The results 

 are given in Table 3 in counts per minute, the 

 uptake (count) being corrected for variations 

 in light incident in different samples on the 

 assumption that, over the range of intensity 

 of illumination employed, the uptake is pro- 

 portional to the illumination. The error 

 (standard error) of each determination due to 

 the statistical variability of counting is in 

 each case, not over five counts per minute. 



For each set of replicate samples, we show in 

 Table 3 the mean and standard deviation. It 

 may be observed that the values of standard 

 deviation are all rather similar, and are not 

 correlated with the means, except for Station 

 9-SC-7 where the value of the standard devia- 

 tion Is very much larger than that at any of 

 the other stations. The large variation at 

 this station appears to be due to the single 

 replicate giving the very high value of 680 

 cpm. which may be aberrant. 



An analysis of variance of the nine sets of 

 three replicates (Table k) , including the 

 suspect sample, indicates that the variance 

 among station means is no greater than could 

 be expected to occur by chance in the light 

 of the variability among replicates within 

 stations. The grand mean of 27 observations 

 is 306.5 cpm., with a standard deviation of 

 90.9. 



Now it may be seen that the value of 680 cpm., 

 deviating by 3fk cpm., from the mean of all 

 observations, is a deviation of over four 

 standard deviations from the mean value, and 

 thus is very unlikely to be a chance event. 

 It appears that this sample is somehow quite 

 aberrant and should be discarded from the 

 analysis. Omitting this sample (Table h) de- 

 creases all variance components very greatly. 

 The analysis of variance with this sample 

 omitted still indicates no difference among 

 stations that could not be expected by chance 



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