value of 10-13% > which must be substracted from 

 light-bottle uptake, is nearly equal to the 

 10°/o positive correction suggested by Steemann 

 Nielsen (1952). The data have not been correct- 

 ed for phytoplankton respiration losses during 

 the hours of darkness. The total CO2 concentra- 

 tion of sea water has been assumed to equal 90 

 mg/l. and all of the productivity calculations 

 have been made using this value. 



12. 



Zooplankton standing crop 



Measurements were made of the standing crop of 

 zooplankton by means of plankton net hauls, 

 using gear and techniques comparable to those 

 presently employed by the California Cooperative 

 Oceanic Fisheries Investigations. At each station 

 an oblique tow was made with a one-m. (mouth 

 diameter) plankton net made of 30XXX silk grit 

 gauze in the body and 56XXX silk grit gauze in 

 the rear section and cod-end bag. The net was 

 lowered from the surface to a depth of approxi- 

 mately 300 m. (1+50 m. wire length) at a rate of 

 50 m. per minute while the vessel was slowly 

 underway and retrieved at a rate of 20 m. per 

 minute. The duration of a single haul, there- 

 fore, was about 32 minutes, on the average. An 

 Atlas flow meter was mounted in the mouth of the 

 net to record the volume of sea water filtered 

 by the net. Flow meters were calibrated before 

 and after the cruise. 



Zooplankton collections were preserved in k" / 

 buffered formalin. Ashore, the collections 

 were filtered and the total "wet" volumes 

 of plankton obtained at each station were 

 measured by displacement. The volume of water 

 sampled by each haul was determined by a 

 method described by the South Pacific Fishery 

 Investigations of the U. S. Fish and Wildlife 

 Service and the displacement volumes were then 

 converted into terms of the volume of organisms, 

 in cu. cm., collected from each 1000 cu. m. of 

 sea water strained. 



13 . Techniques used in the abundance determina- 

 tion of heterotrophic micro-organisms (bac- 

 teria) 



Sea-water samples were collected from various 



depths in the water column with sterile 

 rubber bulbs attached to J-Z water samplers 

 (ZoBell, Marine Microbiology: A monograph on 

 hydrobacteriology, Chronica Botanica, 19^) • 

 The contents of the J-Z samplers were trans- 

 ferred to sterile 200-ml. prescription 

 bottles immediately after arriving at the 

 surface. The bacterial counts were determin- 

 ed by plating 0.1- to 5-0-ml. aliquots of the 

 water samples in duplicate in sterile, 

 plastic, disposable, petri dishes (Falcon 

 Plastics, Culver City, California). The 

 medium had the following composition: peptone 

 (Difco), 5.0 g; yeast extract (Difco), 1.0 g; 

 FeoPOi,., trace; agar, 15.0 g; aged sea water 

 (75°/o), 1,000 ml. as defined by Oppenheimer 

 and ZoBell (The growth and variability of 

 sixty-three species of marine bacteria as 

 influenced by hydrostatic pressure, Jour. 

 Mar. Res., Vol. 11, No. 1, pp. 10-18, 1952). 

 The sterile agar medium was cooled to ^2°C 

 t 2°C and was poured into the seeded plates 

 on a table suspended from the ceiling of the 

 lounge (below decks). The suspended table 

 was weighted underneath to provide stability 

 and steadied with the aid of a second person. 

 Such a free-swinging table proved sufficient 

 to compensate for the roll of the ship in calm- 

 to-moderate seas. The plates were incubated 

 at 31°C t 1°C, for three days or longer 

 before reading on a Quebec colony counter. 

 The high temperature of incubation employed 

 is not customary for marine bacteria. This 

 temperature was the lowest possible aboard 

 ship in the tropics without a refrigerated 

 incubator. This temperature was not too 

 high for surface forms since surface sea- 

 water temperatures were almost as high. 



The results of the bacterial counts taken with 

 the J-Z samples on the return trip from 

 Panama are reported in the noon station data 

 tables. 



On the cruise from San Diego to Panama bacte- 

 rial counts were made from water collected 

 in plastic Van Dorn samplers. This sampler 

 was used since Wood (Heterotrophic bacteria 

 in the marine enviroment of eastern Australia. 

 Australian Jour. Mar. and Freshwater Res., 



