Plankton Volumee 



Crutee: 70 Q-^ 0^'"\ 



of 



/O 



Figure 20. — Plankton-volume data sheet. — A sample copy of a sheet made out for stations 60.50 to 70.80 on cruise 

 7003-"O^on." (This does not match any of the sets of data for which examples are shown in this report.) The data 

 shown here were collected on a special cruise on the CalCOFI grid by a cooperating vessel, Ogon, of the U.S.S.R., 

 to show fractioning of samples (no longer done at this laboratory — see note on description of Set IV in the section 

 on processing data.) These samples were fractioned by agreement with the Russion participants in that each or- 

 ganization would keep one half of each sample for study at its respective laboratory and exchange the data on all 

 samples. 



first step in measuring is to bring the plank- 

 ton plus its preservative to the "proper 

 level" by using the T-guide and float as 

 shown with Figure 22. (Alternative meth- 

 od — If calibrated jars, T-guide, and float 

 are not available, the sample and its pre- 

 servative are poured into a graduated cyl- 

 inder and enough preservative is added or 

 subtracted to bring the level of the liquid to 

 an even milliliter, usually 900 or 1,000; the 

 volume is recorded.) 



A funnel is placed in a clean graduated cyl- 

 inder (see Fig. 24 for specifications), and 

 a 333-/Lt-mesh nylon draining cone (source 

 of specifications — Table 1) is placed in the 

 funnel. 



The plankton and preservative in Step 1 

 (either alternative) are poured into the 

 draining cone (Fig. 23). The plankton is 

 retained in the cone while the liquid drains 

 into the cylinder. The plankton is con- 

 sidered drained when the liquid from the 

 bottom of the cone diminishes to an occa- 

 sional drop. Draining time varies with the 

 size and composition of the sample. 

 The volume of the drained liquid in the 

 cylinder (Fig. 24) is subtracted from the 

 initial volume of plankton plus liquid (Fig. 

 22) — caligrated quart jar or graduate in 

 alternate of step 1. The diflference, the total 

 volume of the sample, is recorded on the 

 data sheet. 



21 



