and inactive chlorophyll a in the northeastern 

 tropical Pacific, caution must be used in the 

 interpretation of the data, particularly with 

 respect to production coefficients. In all prob- 

 ability, much of the rather wide range in 

 production coefficients obtained may be par- 

 tially explained by temporal and spatial varia- 

 tions in these chlorophyll a derivatives. 



The degree of success of the extraction of 

 pigments from the organisms on the filter 

 appears somewhat variable. Almost invariably 

 the residue of particulate matter in the bottom 

 of the test tube after centrifugation appears 

 to be pigmented. Reextraction and centrifuga- 

 tion removes only part of the additional pig- 

 miented material. Thus, some material on the 

 filter is not successfully extracted, and the 

 amount seems to vary from sample to sample. 

 Since microscopic examination of the residue 

 has not been made, it is not known what per- 

 centage is organic. Experience with a limited 

 number of species in culture has shown that the 

 pigments of certain species extract well, 

 whereas others, notably Nannochloris sp., do 

 not (Yentsch and Menzel, 1963). Thus this tech- 

 nique fails to detect an unknown and variable 

 amount of plant pigment. It seems doubtful that 

 the quantity missed ever amounts to more than 

 10 to 20 percent in the tropical regions sampled, 

 but this assumption is unverified. 



PRIMARY PRODUCTION 



Primary production was measured in this 

 study to gain insight into the factors that regu- 

 late this process rather than to attempt semi- 

 quantitative assessment of the productivity of 

 the eastern tropical Pacific. 



Sample Collection and Incubation 



The samples used in the photosynthesis 

 studies were collected in polyvinyl chloride 

 samplers shortly before local apparent noon, 

 or in some in situ studies, one-half to three- 

 quarters of an hour before dawn. The Pyrex 

 incubation bottles, 125 ml., with ground-glass 

 stoppers, were washed in detergent, rinsed 

 three to five times in tap sea water and soaked 

 in weak HCl-sea water (5-10 percent HC 1 by 

 volume) for 2 to 3 minutes and rinsed again 

 three to five times in tap sea water. Each in- 

 cubation bottle was rinsed three times again 

 with water from the sampler before the sample 

 to be incubated was drawn from the plastic 

 sampler. 



In the vessel laboratory, 1.25 to 1.50 ml. of 

 the sample was withdrawn from each sample 

 bottle with a nylon syringe and 1.0 ml. of the 

 C^"^ solution added to the bottle. The C^"^ was 

 introduced well down into the sample with a 

 nylon syringe and stainless steel hypodermic 

 needle modified to deliver a known and constant 

 volume (about 1.00 ml.) The stoppered bottles 



were inverted gently several times to mix 

 the C-'-'* solution and sea water sample. The 

 samples were then incubated. 



At the end of the incubation period the sam- 

 ples were placed in a light-tight box and 

 promptly filtered through 25.4 mm. -diameter 

 HA Millipore filters. The filter and filter 

 assembly were then rinsed with three washes 

 (about 10 ml. each) of surface sea water and 

 the filter pads placed in perforated labelled 

 pill boxes. The pill boxes were stored in cans 

 containing silica gel as a drying agent. After 

 the return of the cruise, the sample filters 

 were fumed over concentrated HC 1 for 15 to 

 20 minutes, redried in a vacuum desiccator 

 over silica gel, and counted. 



Three types of incubation were used to 

 estimate primary production: (1) samples 

 from one or more depths were incubated at 

 sea surface temperatures under constant arti- 

 ficial illumination of 1,000 + 100 ft.-c. (foot- 

 candles) for 4 hours (called laboratory incuba- 

 tion) ; (2) samples from one or more depths 

 were incubated at the sea surface by towing 

 the sample bottles astern of the vessel or were 

 incubated at sea surface temperature in a deck 

 incubator (surface or deck incubation); and (3) 

 samples were incubated in situ at the collection 

 depth between sunrise and local apparent noon 

 or from local apparent noon until sunset 

 (called in situ incubation). 



The artificially illuminated incubator was 

 patterned after one described by Steemann- 

 Nielsen (1957). Illumination was provided from 

 one direction only. Twelve 20-watt General 

 Electric daylight -type fluorescent lamps pro- 

 vided the light source. Temperature was con- 

 trolled by circulating surface sea water through 

 the incubator at a rate of 4 to 12 liters per 

 minute. The temperature of the water in the 

 incubator was usually about 1 ° C. above the sea 

 surface temperature, although differences oc- 

 casionally were as great as 2.5° C. 



The bottles were placed on a wheel or turn- 

 table which rotated slowly (three to six rota- 

 tions per minute) for the duration of the ex- 

 periment (generally 4 hours). 



The illumination in the incubator was moni- 

 tored frequently but at irregular intervals 

 during each incubation series. The monitoring 

 was facilitated by mounting an epoxy-resin- 

 sealed barrier layer photocell (Weston YG 856) 

 on the turntable in such a manner that the cell 

 surface was located in the same plane as the 

 half thickness of the incubation bottles. This 

 cell was connected by gold-plated slip rings 

 mounted on the turntable axle to a shunted 0- 

 to 100- ^a. meter. The meter was installed on 

 the incubator control panel. The cell and meter 

 circuit were calibrated with a Weston Model 

 756 illumination meter (new candle model), 

 with the incubator lamp bank as a light 

 source. 



Although the incubator production measure- 

 ments are expressed in terms of milligrams 



22 



