p 270 



^26 



Ijj 



I- 250 



UJ 



§ 240 



o: 



3 ?^o 



TOP OF 

 THERMOCLINE 



I , , I 



2100 0000 0300 0600 0900 1200 1500 



LOCAL STANDARD TIME 



2100 0000 0300 0600 0900 



FiGtTBE 3. — Vertical distribution of temperature during June 21-23, 1957, at the IGY station. 



Table 2. — Summary of correlations between volumes of 

 zooplankion and certain physical and chemical environ- 

 mental factors 



•Significant at 5- percent level. 

 ••Significant at 1-percent level. 



and about 200 to 300 m., and also the depth from 

 the surface to the top of the thermocline. Changes 

 in volumes of zooplankton and in physical and 

 chemical factors of the environment during the 19 

 months are illustrated in figures 4, 5, and 6. Sur- 

 face values are given in table 3. 



Except for June 1957 and October 1958, the 

 volumes of zooplankton obtained <at night were 

 greater than those collected by day (fig. 4). The 

 ratio of night to day volumes ranged from 0.9 : 1 

 to 3.3 : 1 and averaged 1.8 : 1. 



Volumes of zooplankton sho"wed close correla- 

 tions with salinities and depths of the isothermal 

 layer but not with other environmental factors. 

 Positive correlations were significant at either the 

 5 percent or 1 percent probabilities between vol- 

 umes of zooplankton for day hauls and salinities 

 at the surface and at to 60 m., and for night hauls 

 and salinities at 200 to 300 m. (table 2). Correla- 

 tions between volumes of zooplankton for night 

 hauls and salinities at to 60 m. and for day hauls 

 and salinities at 200 to 300 m. were very close 



VARIAJTIONS IN MARINE ZOOPLANK/TON IN HAWAIIAN WATERS 



91 



