island chain would seem to have definite ecolog- 

 ical significance. 



McGary (195B) pointed out that, on Smith 

 cruises 10 and 12, zooplankton maxima were 

 associated with the cyclonic eddies in the lee of 

 the islands, and concluded that "the occurrence 

 of the zooplankton nnaxima at or near the centers 

 of the cyclonic eddies and the frequent occurrence 

 of high salinities and low tennper atures at their 

 centers are the result of divergent motion which 

 causes some enrichment of the surface water. 

 The slightness of the maxima and the number of 

 exceptions to the increase of salinity and de- 

 crease of temperature at the centers indicate 

 that vertical nnotion is small and intermittent at 

 best. " 



One method, perhaps, of testing for 

 signs of occasional enrichment resulting irom 

 the eddies is to compare the standard deviation 

 of the means of zooplankton volumes obtained 

 from areas with eddies (i.e. areas in which the 

 eddies are centered) with the standard deviation 

 from areas without eddies. If the occasional 

 occurrence of unusually la r g e volumes were 

 particularly associated with the eddy systems 

 (as defined and located by McGary 1955 and 

 Seckel 1 955), then the means from these areas 

 might be expected to have a high variance. In 

 table 3 we show the means and standard devia - 

 tions for 5 cruises of the Smith which provided 

 comprehensive coverage of Hawaiian waters . 

 There is no evidence supporting the assumption 

 as stated above. In fact, the average standard 

 deviation (5.2) for areas without eddies was 

 larger than for areas with eddies (4.8), but the 

 difference was not great. 



According to Seckel (1955), on cruises 

 17 and 21 conducted during late summer months 

 under conditions of normal tradewind weather, 

 the greatest extremes in surface temperature 

 occurred on the leeward side of the island chain; 

 on cruise 21 the surface inorganic phosphate 

 averaged 0.2 \ig at. /L. for the windward side 

 and 0. 3 \ig at. /L. on the leeward side. In re- 

 spect to the zooplankton, on these two cruises 

 the highest variability and the highest average 

 volumes were obtained on the windward side 

 (table 3); the differences between windward and 

 leeward areas are statistically not significant, 

 however. It is of interest that on cruise 20, 

 conducted during a late winter month (March) 

 and also under tradewind conditions, the highest 

 variability and highest average v o 1 u nn e were 

 obtained on the leeward side; again the differ- 

 ences were not statistically significant. It is 

 possible, therefore, that the differences shown 

 in table 3 for five cruises providing comprehen- 

 sive coverage of the Hawaiian area are the re- 

 sult of chance variation; they supply no conclu- 

 sive evidence of enrichment downstream from 

 the islands as the result of eddy systems, up- 

 welling, land drainage, or other influence of the 

 littoral waters. 



Although we have collected a rather large 

 nunnber of plankton samples in Hawaiian water s 

 during the years 1950 - 1954, they are not ade- 

 quate to describe seasonal variations or differ- 

 ences among years. In figure 7 we show the 

 mean volumes obtained on all cruises employing 

 a uniform sannpling method (i. e, oblique hauls to 

 200 meters depth with 1 -meter nets of 30XXX 

 grit gauze). Some of the cruises gave compre- 

 sive coverage of the Hawaiian area, whereas 



Table 3. --Comparison of mean zooplankton volume (x) , as cc./lOOO m. , and standard deviation (s) 

 of the mean, for 6 subareas of the windward and leeward Hawaiian waters, sampled on 

 5 cruises of the Hugh M. Smith . An asterisk indicates the presence (center) of an eddy 

 in the subarea at time of sampling 



