LABORATORY PROCEDURES ?J 



Zooplankton 



First the few organisms with longest 

 dimension greater than 2 cm. were removed 

 from each sample, identified as precisely as 

 possible, and their displacement volume deter- 

 mined. Then the volume of the remainder and 

 bulk of the sample, i.e. , those organisms with 

 longest dimension less than 2 cm. , was deter- 

 •mined' in measuring the displacement volume, 

 the sample was poured into a draining sock of 

 56XXX grit gauze to filter off the preserving 

 liquid. When the samiple stopped dripping, it was 

 transferred to a graduated cylinder of appropriate 

 size (usually 50- or 100 -ml. capacity). By means 

 of a burette, a known volume of water was added 

 to the drained plankton. The difference between 

 the volume of the plankton plus the added liquid 

 and the volume of liquid alone was recorded as 

 the displacement or wet volume of that portion 

 of the sample. 



Following the usual procedure at our 

 laboratory, the volume of all organisms less 

 than 2 cm. in length plus the volume of organ- 

 isms 2 to 5 cnn. inlength that might be considered 

 of significant nutritional value were combined 

 to give a single volume measurement for each 

 sample. This figure was divided by the estima- 

 ted amount of water passing through the net to 

 obtain the volume of zooplankton, as food, per 

 unit of water strained. 



dimension which had been removed previously) 

 was computed by use of the following formula: 



when 



E = total estimated number 



C = counted number 



A = area of counting cell 



f = fraction of total sample in the covinting 



cell 



a = area of field 



n = number of fields counted 



The estimated number of organisms per unit of 

 water strained was then calculated by dividing 

 figure E by the amount of water passing through 

 the net. 



Midwater Trawling 



In the laboratory each trawl collection 

 was split into two size categories, organisms 

 less than 2 cm. and organisms greater than 

 2 cm. longest dimension. Because of the meah 

 size of the trawl net, the first category was not 

 sampled in a quantitative nnanner. Each size 

 group was further sorted into kinds of organ- 

 isms, with identifications being made to the 

 most precise degree that seemed practical. 



In coiinting the plankton a fourth or an 

 eigth of each sample was spread out in a shal- 

 low, rectangular dish 1 5 x 20 cm. , ruled in 1 - 

 cnn. squares. All organisms greater than 0.5 

 mm. longest dimension were counted in 10 fields, 

 each 1 cm. square. The estimated number of 

 organisms in the total sample (not including the 

 few organisms greater than 2 cm. longest 



2/ 



— We should like to acknowledge the 



assistance of other POFI personnel in proces- 

 sing the EASTROPIC data and collections. John 

 Van Landingham was responsible for the chemical 

 determinations; Mary Lynne Godfrey and Ella 

 Mendiolafor processing the oceanographic data; 

 Thomas Hida, Robert Iversen, and Hilda Ching 

 for the zooplankton counts and volume mea- 

 surements; Allen Shimomura for the midwater 

 trawl data; and Tamotsu Nakata drafted the 

 figures. 



Mikihiko Oguri, of the University of 

 Hawaii, made the C'^'' counts and chlorophyll 

 measurements . 



The number and displacement volume 

 were determined for each kind or group of or- 

 ganisms identified. In some instances, the total 

 number of certain organisms in the less than 

 2 cm. category was estimated from the number 

 in a subsample. Table 5 gives the total num- 

 bers and volumes of each of the two size cate- 

 gories. The detailed composition of the 

 collections will be reviewed in a later report. 



Carbon Fixation Measurements 



Counting the C'- 



In the University of Hawaii laboratory 

 at Honolulu, the filter discs bearing the C 

 fixed in the sample bottles were mounted on 

 Tracerlab E-8B planchette holders, which had 

 been lightly greased to retain the discs. The 

 counting was done with a Tracerlab SCI 6 win- 

 dowless gas flow counter and a Tracerlab 

 1000-Scaler, or a Nuclear -Chicago 161A-Scaler, 

 using as the gas in the counting chamber a mix- 

 ture of U. S. P. XII Helium bubbled through 

 ethanol at -15° to -5°C. 



10 



