deck incubation results may be compared, 

 however, as well as deck incubation and in 

 situ results. 



The data used in this analysis (table 14) were 

 collected by Forsbergh and others (Scripps 

 Institution of Oceanography, University of 

 California, 1961, STEP I Expedition, II) in the 

 eastern tropical Pacific, by methods and 

 equipment believed to be comparable to those 

 of the present investigation. The data were 

 selected from those of Forsbergh; the criterion 

 for selection was that duplicate values be 

 available for each type of incubation at each 

 station. This criterion was selected because 

 data from the present study were based on the 

 mean of two sample values. The results of a 



Table 1<4. — Primary production rates of deck 

 incubated and trailed surface samples in the 

 eastern tropical Pacific Ocean, STEP-I Expe- 

 dition, 1960^^2 



■"• Scripps Institution of Oceanography, 

 University of California, 1961, STEP I Expedi- 

 tion, Part II. 



2 rd =0.86, p < 0.01 



Z = 68 — = 1.49, p = 0.14 (, two-sided 

 \/2,071 test) 



^ Observations made in the period September 

 18-26 were not given station numbers. 



statistical analysis of the data (table 14) were 

 similar to those of the previous example, 

 namely, the two types of nneasurements are 

 significantly correlated (r^=0.86, p < 0.01). 

 The results of the Mann-Whitney U test (cal- 

 culated as Z in table 14) indicate that the values 

 were probably drawn from the same population. 



As in the preceding example, results from 

 these two techniques differ. The trailed 

 samples received more agitation than the deck 

 incubated samples. Although the spectral dis- 

 tribution of the radiant flux is probably nearly 

 identical in the region of photosynthetic ac- 

 tivity, the trailed samples received alternating 

 or pulsating flux as a result of focusing of 

 radiant flux by the surface waves and ripples. 

 It was different in the deck incubator. 



The comparison between deck incubator and 

 in situ methods is drawn from six sets of data 

 only. This number probably is not adequate, 

 but since no other comparative material is 

 available, the data have beenused. The STEP-I 

 data of Forsbergh and others and results of 

 the statistical analysis are presented in table 

 15. These data show, as was true with the 

 laboratory incubator-in situ comparisons 

 (table 13), that deck incubator and in situ water 

 column rates are significantly correlated and 

 that no difference exists between the sampled 

 populations (p = 0,82). 



Notwithstanding the difficulties that may be 

 experienced occasionally with the C method 

 (such as high dark-bottle counts), the above 

 data and analysis show that either the labora- 

 tory or deck incubator method provides data 

 which may be used to estimate in situ pro- 

 ductivity. Errors of estimate from these 

 indirect methods are probably somewhat 

 variable in time and space. Nonetheless, the two 

 indirect methods provide useful information on 



Table 15. — Simultaneously observed deck 

 incubator and in situ production rates at 

 stations, in the eastern tropical Pacific, 

 STEP I Expedition, 1960^' ^ 



Scripps Institution of Oceanography, 

 University of California, 1961, STEP I Expedi- 

 tion, Part II. 



2 rd = 0.95 < 0.02 > 0.01 



U = 16, p = 0.82 I, two-sided test) 



27 



