SOME TIDE- WATER COLLECTIONS OF MARINE 



DIATOMS TAKEN AT HALF-HOUR 



INTERVALS NEAR SAN DIEGO, 



CALIFORNIA 



BY 



WINFBED E. ALLEN 

 (Contribution from Scripps Institute for Biological Research of the University of California) 



In the last two or three years the scientific staff of the Scripps 

 Institution has been giving much attention to variations of hydrogen 

 ion concentration (pH) in sea water and to the relationships of these 

 variations to other phenomena, including variations in abundance of 

 phytoplankton. 



The intricacies of the oceanic complex are so profound and the 

 difficulties of observation are so great that it has, so far, been found 

 impossible to make very satisfactory interpretations of conditions 

 observed. Under present limitations it is evident that adequate 

 foundation for interpretations can be laid only at the expense of 

 much time and energy. There is, however, the possibility that valu- 

 able indications as to the true path to reliable interpretations may be 

 obtained through studies of less intricate complexes (e.g., small fresh- 

 water lakes) or of special conditions involving marked differences in 

 factorial relationships. 



After much consideration it was concluded that intensive study 

 of tide-water at the entrance to a small bay might furnish valuable 

 indications of the type mentioned. At 9 p.m. of November 3, 1922, 

 our chemist, Mr. E. G. Moberg, our oceanographer, Dr. G. F. McEwen, 

 and an assistant in hydrography, Mr. T. Woodward, began a series 

 of collections of water samples at the entrance to Mission Bay ("False 

 Bay") about six miles north of Point Loma, the entrance to San 

 Diego Bay. These collections were taken at intervals of thirty minutes 

 up to 5 p.m. on November 4. At the same intervals, beginning at 

 9 :30 p.m., twenty-five liters of water was filtered through a small net 

 of No. 25 bolting silk and handled according to our regular method 

 (see Allen, 1921). The present paper discusses the results of that 

 work from the standpoint of the phytoplankton as represented by 

 diatoms. Particular attention was given to variations in numbers 



