a 1+7 -mm. type HA, plain, white Millipore 

 filter. The filter membranes were dried in a 

 vacuum desiccator and then extracted with 3 

 mis. of 90°/ acetone (glass redistilled) in 

 the cold (ca. 10°C) and dark for approximately 

 10-12 hours. The sample was then centrifuged 

 until clear. The supernatant was next decanted 

 into a volumetric flask or cylinder and the 

 remaining precipitate in the tube resuspended 

 with 1-2 mis. of 90% acetone, centrifuged, 

 and the supernatant combined with that obtain- 

 ed previously. Recentrifugation of the 

 combined extracts was frequently necessary to 

 reduce turbidity. This extract was finally 

 diluted to 6 ml., and its optical density was 

 measured in a 10-cm. semimicro-absorption cell 

 at 750, 665, 61+5, and 630 mu with a Beckman 

 model DU spectrophotometer. Turbidity correc- 

 tions were made on the basis of the sample 

 transmission at 750 mu and the concentrations 

 of chlorophyll "a" have been calculated from 

 the equations of Richards with Thompson (Jour. 

 Mar. Res., Vol. 11, No. 2, pp. 156-172, 1952). 



11. Primary production 



lit- 

 The C method was employed in these studies 



to determine the rate of carbon fixation by 

 the phytoplankton. The C 1 ^ solution was 

 prepared and standardized in the manner 

 described by Steemann Nielsen ('Jour, du Cons., 

 Vol. 18, No. 2, pp. 117-l 1 +0, 1952) with the 

 exception that glass redistilled water rather 

 than artificial sea water was used as the 

 solvent. The C^ solution employed was filter- 

 ed through an HA Millipore filter and put in 

 1-ml. glass ampules which were autoclaved. 

 The radioactivity of the samples was measured 

 with an NMC-PC#1 proportional counter. 



In situ surface productivity was measured 

 using samples dipped from the sea surface with 

 a plastic bucket at either sunrise or local 

 noon. The samples were placed in clean, well 

 aged, 250-ml. Pyrex bottles inoculated with 

 C^ , and trailed astern of the vessel, just 

 under or on the top of the sea surface, until 

 local noon or sunset, respectively. The 

 samples were filtered immediately and placed 

 in a vacuum desiccator for drying. 



The in situ vertical measurements of productiv- 

 ity were carried out in the following manner. 

 A water sample was collected at each desired 

 depth with the plastic Van Dorn-type sampler 

 shortly before daylight. The samples were 

 transferred to clean, well aged, 250-ml. 

 Pyrex bottles and the C- 1 -^ solution injected 

 with a plastic hypodermic syringe and stain- 

 less steel needle. The samples were re- 

 suspended at or slightly before dawn, at 

 approximately the depth ( + 1 m.) at which 

 they were collected, on a weighted rope 

 supported by a free-floating glass buoy (ll+ 

 in. in diameter) enclosed in a cord netting 

 and attached to a bamboo pole bearing a flag 

 at its top. The surface sample was attached 

 to the side of the glass buoy, just under 

 the sea surface. The samples were collected 

 at noon, local time, and were promptly filter- 

 ed and dried for counting. 



The samples incubated on shipboard were 

 inoculated with C in the same manner as the 

 in situ and trailing bottle material. The 

 incubator itself was similar to that employed 

 by Steemann Nielsen (Jour, du Cons., Vol. l8, 

 No. 2, pp. 117-llK), 1952). Temperature con- 

 trol was achieved by circulating subsurface 

 sea water through the water bath at a rate of 

 It— 6 1 . per minute . The temperature in the 

 bath fluctuated somewhat but never exceeded 

 the sea-surface temperature by more than 

 2.3°C, and usually by less than 1°C. 

 Temperatures less than that of the sea sur- 

 face were not observed in the incubator . The 

 samples were illuminated by a bank of 10 

 daylight-type fluorescent lamps. The lamp 

 bank was moveable and was the means employed 

 in keeping the intensity of light at the 

 bottles at 1000 foot-candles. 



The data presented in these pages have not 

 been corrected for dark-bottle uptake, the 

 isotope effect, or for phytoplankton 

 respiration. In our experience the dark- 

 bottle uptake averages 10-13*% of the uptake 

 in the illuminated bottles when the experi- 

 mental period does not exceed eight hours, 

 although dark uptake may exceed this if the 

 bottles are not washed carefully. This 



