BIOLOGICAL RESULTS OF LAST CRUISE OF CARNEGIE 



showed 100 or more cells per liter, and in the tropics 

 there were no counts of dinoflagellates as great as one 

 hundred. 



sented by only two samples (0.09 to 0.29 lower). Mean 

 phosphates for the richer samples are higher in every 

 case except one, which is represented by only two sam- 



Table 2. Summary of the physical and chemical data and phytoplankton counts from Carnegie collections, 

 1928-1929, in the northern, tropical, and southern regions of the Pacific Ocean 



Although they never attained the great numbers that 

 were sometimes reached by the diatoms, the dinoflagel- 

 lates in the poorer samples often outnumbered the dia- 

 toms. In the southern region twenty-nine samples out of 

 the forty-eight (60 per cent) contained more dinoflagel- 

 lates than diatoms, whereas for the northern region this 

 applied for sixteen samples out of one hundred and 

 twelve (14 per cent), and in the tropical region for thirty 

 out of one hundred and forty-three (21 per cent). The 

 dinoflagellates outnumbered the diatoms in twenty-five 

 per cent of all the samples. 



Density of Phytoplankton and 

 Environmental Factors 



In regions which have such a wide variation in con- 

 ditions, and where the plankton life is so poor general- 

 ly, it would seem that no correlations could be found be- 

 tween the abundance of plankton and environmental con- 

 ditions. If we arbitrarily separate the samples, how- 

 ever, into those showing less than 100 combined diatom 

 and dinoflagellate cells per liter and those with more 

 than that number, and compare the data accompanying 

 them, some interesting relations stand out. Table 3 

 shows the mean values for certain environmental factors 

 investigated for the waters containing over 100 cells per 

 liter and for those containing less than 100 cells for 

 each level in each region. It will be seen that the mean 

 temperatures for samples with over 100 cells are lower 

 in all cases (3f41 to 8.°77 C lower). The mean salinities 

 for the richer samples are consistently lower (0.03 to 

 0.99 o/oo lower). In the richer samples the pH values 

 are lower except in one case where the mean is repre- 



ples (17 to 103 mg PO4 per cubic meter higher). As 

 regards the percentage saturation of oxygen, in one case 

 the oxygen means for the richer and poorer samples is 

 the same, in three instances the mean saturation is less 

 in the richer samples, and in one case it is greater. The 

 meager silicate data do not suggest any correlations be- 

 tween number of plant cells and silicate content of the 

 water. 



To summarize we may say that in general the rich- 

 er samples occurred in water of lower temperature, 

 lower salinity, lower pH, and higher phosphate content, 

 whereas little correlation could be found between num- 

 bers of plant cells and percentage saturation of oxygen, 

 or between numbers of plant cells and quantity of dis- 

 solved silicate. 



Before discussing these relations further, let us 

 compare conditions in the open ocean where plankton is 

 scarce, with conditions in a coastal region where high 

 productivity is the usual thing. Bigelow and Leslie 

 (1928) investigated the waters of Monterey Bay, Cali- 

 fornia, in July 1928. Although their work was carried 

 on in midsummer when phytoplankton is usually not ex- 

 pected to be most abundant, yet they report over one 

 million diatom cells per liter as the average for the 

 bay. This, therefore, represents an area with water 

 favorable for diatom production. Table 4 shows a com- 

 parison of the Monterey Bay surface conditions with 

 those at the Carnegie northern stations. The Carnegie 

 stations presented here were occupied from May to Oc- 

 tober 1929. The data in this table tend further to show 

 that relatively low temperature, low salinity, high hy- 

 drogen-ion concentration, and high phosphates are in- 

 dicative of productive waters, the conclusions arrived 



