a broad area of absences and low abundance in the 

 lower half of the north area, compared with a very 

 narrow band of absences or low abundance on the 

 western margin of the south area. 



Contouring and testing the density of all calanoid 

 copepods as one group obscures much detail but does 

 indicate major patterns (Fig. 10). The west area was 

 statistically separable from the north and south areas 

 because of the high abundance in the lower half of the 

 west area. The north and south areas were not statisti- 

 cally separable and were characterized by generally 

 few calanoids. Lowest abundances in the north area 

 were in the northeast sequences of stations, consider- 

 ably off center from the areas of lowest abundance for 

 the individual species contoured. In the south area, 

 the four stations of lowest total calanoid densities (sta- 

 tions 63, 72, 86, and 87) were the same stations con- 

 tributing to the low mean densities of Acartia lon- 

 giremis. Calanus finmarchiciis, and Eucalanus bungii. 



In general, the west area had significantly higher 

 mean concentrations of zooplankters than the com- 

 bined north and south areas except for Aglantha 

 digitale and Clione limacina. Although not statisti- 

 cally separable, the difference between west and east 

 concentrations of Acartia longiremis (Fig. 5) is proba- 

 bly real. 



The north area had statistically higher mean densi- 

 ties of Aglantha digitale and Eucalanus bungii and 

 lower mean density of Sagitta elegans. After deleting 

 the exceptionally high count of Centropages 

 abdominalis at station 62, the density of C. 

 abdominalis was also statistically higher in the north 

 than in the south area. Variances of A. digitale, C. 

 abdominalis, and E. bungii were statistically higher in 

 the north area than in the south area, as was the var- 

 iance of Clione limacina after deletion of exceptionally 

 high values from station 63. Although the differences 

 were not always statistically significant, the north area 



Figure 10. — Abundance of calanoid copepods (all species) contoured 

 in powers of 4 per 100 m^. 



had generally higher means and variances than the 

 south area. 



Temperature 



The contours of temperature (Fig. 11) resemble 

 those of zooplankton abundance. The area enclosed 

 by the 0°C contours between Cape Lisburne and Point 

 Lay most closely approximates the area of lowest 

 zooplankton diversity (Fig. 1) as well as areas of low 

 abundance for Aglantha, Clione, Centropages, 

 Eucalanus, Pseudocalanus, and total calanoid 

 copepods (Fig. 2, 4, 7, 8, 9, 10). To the north, tempera- 

 tures rise to over 3°C and then drop, forming a series 

 of contours that parallel changes in abundance of these 

 same five zooplankters, plus Sagitta, total calanoid 

 copepods, and perhaps Calanus. The area northwest 

 of Cape Lisburne generally has wider contour spacing 

 of temperatures from 1° to 3°C and generally higher 

 abundance of zooplankton. If temperature is the major 

 physical factor controlling zooplankton abundance, 

 areas with temperatures below 0°C or with strong 

 horizontal gradients probably had a history of condi- 

 tions (either too cold or unstable) that prevented de- 

 velopment of large populations. The areas of broad 

 temperature contours probably represent more stable 

 conditions that would allow denser populations of 

 zooplankton to develop. 



Salinity 



The distribution of zooplankton did not appear to be 

 - associated with salinity. The salinity contours (Fig. 

 12) did not correspond well with the zooplankton con- 

 tours, particularly in the 10 m and bottom contours. 

 Thus, although the nearshore stations were less saline 

 than the offshore stations, these differences were not 

 associated with differences in zooplankton abundance. 



Dissolved Oxygen 



The horizontal contours of dissolved oxygen con- 

 centration (Fig. 13), especially at the surface and 10-m 

 depths, may be more indicative of recent physical 

 processes and lowering temperatures than biological 

 processes. Although there appears to be an inverse 

 relationship between zooplankton abundance and ox- 

 ygen concentration, comparison of zooplankton abun- 

 dance with percent saturation of dissolved oxygen 

 (Fig. 14) and theoretical oxygen depletion yielded no 

 significant relationships. The cold-water area between 

 Cape Lisburne and Point Lay had low zooplankton 

 abundance and high oxygen concentrations. The sta- 

 tions northwest of Cape Lisburne had warmer waters, 

 more zooplankton, and generally less oxygen. West of 

 Point Lay, nearshore stations (where lowered salinity 

 or increased wave action may have effected greater 

 oxygen solution) had higher oxygen concentrations, 

 whereas offshore stations had lower oxygen concen- 

 trations and moderately high populations of Aglantha 



12 



