THE PHYTOPLANKTON 



Table 3. Comparison of the physical and chemical data for water containing more than 100 diatom and 



dinoflagellate cells per liter with that found to contain less than that number from Carnegie 



collections, 1928-1929, in the northern, tropical, and southern regionsof the PacificOcean 



Region 



Depth 



in 

 meters 



Means for number of samples with 



>100 cells 



<100 cells 



>100 cells 



<100 cells >100 cells <100 cells 



Northern 

 Tropical 

 Southern 



Northern 

 Tropical 

 Southern 







50 



100 







50 



100 







50 



100 







50 



100 







50 



100 







50 



100 



Temperature, °C 



14.23 (17) 

 11.92 (10) 

 10.45 (2) 



23.24 (12) 

 20.55 (2) 

 13.90 (1) 



16.90 (1) 



23.00 (22) 

 17.87 (30 

 14.34 (31) 



26.72 (42) 

 24.07 (46 

 22.20 (40) 



20.31 (18) 

 17.45 (16 

 15.38 (14) 



33.65 (17) 

 33.83 (10 

 33.71 (2) 



35.00 (12) 

 34.74 (2) 

 34.99 (1) 



34.05 (1) 



Salinity, o/oo 



34.64 

 34.29 



22) 

 30) 

 31) 



42) 

 46) 



34.24 



35.03 

 35.33 

 35.42 (40) 



34.91 (18) 

 34.73 (16 

 34.65 (14) 



Hydrogen-ion, pH values 



8.14 (16) 8.30 (22) 

 8.11 (9) 



8.15 (2) 



8.15 (12) 



8.04 (2 

 7.84 (1) 



8.05 (1) 



Phosphate, mg/m^ 



11 (22 

 31 (30 

 59 (30 



22 (42 

 44 45 



69 (15) 

 92 (8 

 84 (1) 



39 (12) 



30 (2) 



159 (1) 



46 (1) 



56 (39 



21 (18 

 27 (16 

 34 (14 



Oxygen saturation, o/o 



98 (5) 98 (15) 



99 (4 103 (16) 

 100 (1) 96 (15) 



83 (1) 95 (5) 



15 (1) 91 4) 



51 (6) 



93 (2) 



;!;;!!!!!!! "W'd) 



Silicate, mg/m^ 



0.26 (2) 0.57 (13) 

 0.30 (1) 0.57 (15) 

 0.60 (12) 



0.37 (3) 



1.50 (1) 0.40 (2 

 0.88 (3) 



at from a study of the Carnegie data alone. They fur- 

 ther indicate that the abundance of diatoms bears little 

 relation to the silicate content of the water or to the 

 percentage saturation with oxygen during the summer at 

 least. 



Conditions at La Jolla (Allen, 1928) on the coast of 

 southern California during the second quarter of the 

 year when diatom production is the greatest, are simi- 

 lar to conditions at Monterey in July, so that region will 

 not be discussed. 



Lewis (1927) in studying surface catches of phyto- 

 plankton off the coast of Oregon concludes that the 

 colder water is more favorable for the production of 

 diatoms. Water with temperatures below 11° C main- 

 tained a greater production than water above that tem- 

 perature. 



Table 4. Comparison of surface conditions at Carnegie 

 northern stations with those at Monterey Bay 



a Since Bigelow and Leslie did not include pH de- 

 terminations in their analyses, this value is the ap- 

 proximate mean of the second quarter of four years 

 at La Jolla, California, taken from Moberg (14). 



VERTICAL CIRCULATION AND REPLENISHMENT OF NUTRIENTS 



The data presented here show that certain condi- 

 tions usually accompany a growth of phytoplankton. 

 In any study of the relation between the abundance of 

 phytoplankton and environmental factors, the charac- 

 teristics of a phytoplankton pulse must be kept in mind. 

 Atkins (1928) and others have found that when favor- 

 able conditions occur, such as an abundance of nutri- 

 ent salts and sufficient illumination, a rapid growth of 

 phytoplankton is initiated which continues until the nu- 

 trients are exhausted. If one were to examine the 

 plankton and the existing conditions of the environ- 

 ment at different times during the progress of the pulse, 

 different correlations would be found at different stages. 

 Just before the rapid growth begins there is a sparse 

 population in the presence of favorable conditions, such 

 as high concentrations of nutrients. In other words. 



there is a negative relation between abundance of plank- 

 ton and abundance of nutrients. After rapid growth has 

 started there is a dense population occurring with com- 

 paratively high concentrations of nutrients, or a positive 

 relation between abundance of phytoplankton and of nu- 

 trients. Near the close of the pulse, when the nutrients 

 are practically depleted, there is a dense population in 

 the presence of low concentrations of nutrients which 

 presents a negative relation again. Still further, after 

 the close of the pulse, the decay of the organic detritus 

 may result in a regeneration of nutrients in the upper 

 levels which creates another minor pulse, but before 

 this pulse begins there occur together again high con- 

 centrations of nutrients and a sparse population ofphyto- 

 planktonic organisms, a negative relation again. 



It is obvious, therefore, that any correlations be- 



