stations (n = 18), and summer stations (n = 22), 

 respectively, are 



Y = 2.92 +4.10" X5-O.02O8X4- 0.00590* X3- 0.00305X2-0.00018X1 



Y =3.83 + 2.49X5 - 0.0600 X4- 0.0128»*X3- 0.0427 X2- 0.00042 Xj 



Y = 1.16 - 3.51X5-0.234X4+0.00117 X3+O.O447X2 +0.00030 X J 



These are all significant, and the values of 

 R^ are respectively 0.431, 0.638, and 0.638. 

 Similar equations disregarding X2 and X^ are 



Y= 2.77 + 4.26»« X5 - 0.218* X4 - 0,00561» X3 



Y = 2.73 + 2.36 X5 - 0.117 X4 - 0.0115** X3 

 Y= 3.16 + 4.93** X5 - 0.372** X4 +0.00004 X3 



These are all significant, with R"" slightly 

 lower than before (respectively, 0.424, 0.558, 

 and 0.558) and the respective standard errors 

 of estimate slightly higher than before, and 

 they are more informative as to the depend- 

 ence of zooplankton upon different physico- 

 chennical properties at the two seasons. The 

 light attentuation coefficient is considered a 

 substitute for a measurement of phytoplankton 

 standing crop, in this context, and shows the 

 expected relation to zooplankton in the summer 

 only. 



The standard error of estimate for the first 

 of these six equations, applied to the nnean 

 zooplankton volume of the series which was 

 74 ml. /l, 000 m.^ , yields upper and lower 95 

 percent confidence limits of 129 and 42 

 ml. /l, 000 m.3. Most planktologists, from a 

 knowledge of variability in zooplankton catches 

 from nonvertical hauls (e.g., Silliman, 1946), 

 would set limits as wide as these or wider, 

 around a similar value. Thus it is possible 

 that zooplankton standing crop could be esti- 

 mated at least as well from the above-men- 

 tioned physico-chemical measurements as 

 from measurement of a sample of the zoo- 

 plankton itself. 



With a different set of independent varia- 

 bles (X5. . . .Xj, for chlorophyll a, mixed layer 

 tennperature, mixed layer depth, surface in situ 

 production, and mixed layer oxygen, respec- 

 tively) significant regressions were again 

 obtained for all stations, winter stations, and 

 summer stations, but standard errors of 

 estimate were slightly higher than before. 

 Thus this combination, which includes two 

 variables that it would be extremely difficult 

 to measure on an unmanned moored station, 

 would probably be less efficient than the 

 other as far as estinnating zooplankton is 

 concerned. Of the individual coefficients only 

 those for chlorophyll a (both seasons) and 

 mixed layer depth (winter only) were sig- 

 nificant. 



The interpretation of these results in re- 

 spect to cause-and-effect relations is obviously 



difficult. They suggest hypotheses that can 

 be nnore rigorously checked by statistical 

 studies of smaller groups of the data (station 

 groups m.ore homogeneous in time and space, 

 fewer variables in different combinations, 

 etc.), and this is expected to be the next step 

 in the investigation. 



The relationships for summer stations seem 

 to confirm the expectation better than those 

 for winter stations, e.g., more obvious de- 

 pendence of productivity on phosphate and of 

 zooplankton on k (considered as a measure 

 of phytoplankton standing crop). This suggests 

 that the steady-state assumption is more 

 nearly valid for summer than winter (cf. fig. 

 13). However, the differences may merely 

 reflect the fact that the summer stations are 

 the more homogeneous as to time (all data 

 from one cruise). 



Zooplankton-Micronekton Relationships 

 (M. Blackburn) 



The measurement of micronekton volumes 

 is complete only for catches by the large 5-kn. 

 net (fig. 10) on cruises TO-58-1 (SCOT) and 

 TO-59-1. 



Figure 12 shows the distribution of standing 

 crop of total micronekton on TO-58-1. It 

 resembles published charts of distribution 

 of standing crop of zooplankton (Brandhorst, 

 1958) and tuna (Griffiths, 1960; Alverson, 

 I960) in the way values diminish from coastal 

 to offshore waters, and to some extent in the 

 location of richer and poorer areas along the 

 coast. A statistical consideration of this re- 

 semblance to tuna standing crop appears 

 below. In this section only the connection 

 with zooplankton, which was measured at 

 most night stations when nnicronekton hauls 

 were n-iade, is discussed. It is obviously im- 

 possible to connect these night observations 

 directly with the longer series of noon ob- 

 servations discussed above, which were made 

 at different stations, but ways can probably 

 be found to combine the two series when the 

 occasion demands it. 



The right-hand panels of figure 13 show 

 the significant relationship between total 

 micronekton and zooplankton for Expedition 

 SCOT stations (April- June 1958), and the cor- 

 responding nonsignificant relationship for 

 stations on TO-59-1 (January- February 1959). 

 The geographical distribution of stations was 

 different on each cruise. For SCOT stations 

 significant correlations were found also be- 

 tween zooplankton and each component of the 

 micronekton except large Crustacea. Data for 

 stations north of 23° N. (Baja California re- 

 gion) have been excluded, since there were 

 only a few stations and the plotted data did 

 not agree well with those from tropical areas. 



35 



