It vfas stated earlier (po 30; that no significant differ- 

 ences were found among stations nor among visits for the zooplankton 

 voliunes obtained along the north-south section just west of Oahu during 

 the sumnier and fall of 1951 o For this same group of stations we em- 

 ployed an analysis of variance with tv/o-way classification to examine 

 the temperature at the 10-meter depth (table 12) and also depth to the 

 70° isotherm (table 13) for evidence of changes in thermal character- 

 istics during this period of timeo Frorn the analyses we conclude that 

 for the temperature at 10 meters there were highly significant differ- 

 ences (P < OeOl) among stations and among visits during the period cf 

 observations. The arithmetic means for visits show that the teii53Qr- 

 ature of the surface layer fluctuated considerably durir.g the period of 

 observatioRo In late September the temperature was higher than in Julys 

 the cooling which took place during the first part of October was 

 followed by a rise in late October and the highest mean of the group o 

 The figures representing depth to 70°, however, showed no significant 

 difference (P >0.05) among stations or among vis its « 



The zooplankton means (table 9) show peaks in July and late 

 October with reduced volumes in September and early October. The only 

 justifiable conclusion appears to be that during the period from July 

 through October 1951, which bracketed the end of the skipjack season 

 for that year, there ivere significant changes in temperature in the 

 surface layer which were not closely correlated with changes in the 

 depth of the 70° isotherm or in the zooplankton population o 



Inorganic phosphate 



On meridional sections crossing the Equator in the central 

 Pacific we have found highly significant positive correlations between 

 zooplankton abundance and ixiorganic phosphate concentrations (King and 

 Demond 1953) » V^'e thought it of interest to investigate this relation- 

 ship for the Hawaiian areao A comparison of adjusted zooplankton volumes 

 and surface inorganic phosphate shewed confusing results o On Smith 

 cruise 12 there was no significant correlation, but on Smith cruise 17 

 of the following year (table 12) the correlation was highly signifi canto 

 Figure 15 shows lines of equal phosphate concentration as found on these 

 two cruises o There is no obvious pattern in the variations shown by 

 the cruise 12 data<, The cruise 17 data, howe\'-er, show a definite east- 

 west gradient of increasing phosphate values with the greatest zooplank- 

 ton volumes being obtained in regions of high phosphate concerstrationo 

 The meaji zooplankton and phosphate values for these two cruises provide 

 an interesting comparison (table 14) o Cruise 12, in the fall of 1951, 

 had relatively low mean values for both zooplankton and phosphate, while 

 cruise 17, in the fall of 1952 c, had high values for both means « 



Dissolved Oxj-'gen 



In the equatorial region of the central Pacific, where waters 

 with reduced oxygen content occur in the region of xipwelling, a signi- 

 ficant negative correlation was found betv-reen zooplankton volumes and 

 dissolved oxygen as percent saturation (King and Demond 1953). Oxygen 

 and zooplankton data from Smith cruise 10 were examined for evidence of 



42 



