WIEBE ET AL.: RELATION OF VOLUME, WET AND DRY WEIGHTS, AND CARBON 



Table 1. -Number of observations and symbol designation for each cruise or area from which zooplankton samples were collected. The 



symbols are used in Figures 1 and 3-5. 



iData from Menzel and Ryther (1961). 



^Omitted, bad data. 



3See Be et al (1971) for geographical and seasonal coverage. 



"•Data from Be (footnote 5). 



Displacement volumes were measured by one of 

 two techniques. The Mercury Immersion method 

 of Yentsch and Hebard (1957) was used to deter- 

 mine the values given by Menzel and Ryther 

 (1961-Bermuda), by Be et al. (1971-North Atlantic) 

 and Be (1973-unpubl. data for the South Atlantic).^ 

 A modified version of the Mercury Immersion 

 technique was used to measure displacement 

 volumes on Gosnold 140, but further work has 

 shown that the method has significant variable 

 errors and is unreliable (Grice and Wiebe unpubl. 

 data). We have not, therefore, used the Gosnold 

 140 displacement volume data. All other 

 displacement volumes were measured by the 

 method described by Ahlstrom ami Thrailkill 

 (1963) after removal of all organisms larger than 5 

 cc. For split samples, organisms larger than 5 cc 

 were removed prior to the split. On Gosnold 166, 

 displacement volumes were run prior to sample 

 preservation (see Vaccaro et al. 1972 for data) and 

 again 2 yr after preservation. Contrary to the 

 findings of Ahlstrom and Thrailkill (1963), 

 shrinkage did not occur (Figure 2). These samples 

 were, however, heavily dominated by copepods 

 (Wiebe et al. 1973) which are least likely to under- 

 go shrinking. 



Wet weight was measured by straining the 

 plankton through a 333-/i,m plankton gauze, rins- 

 ing with freshwater, and blotting the remaining 

 mass on absorbant paper towels until water was no 

 longer absorbed onto the towel. The biomass was 



then transferred to a pre-weighed glass jar with a 

 stainless steel spatula. The jar was weighed on a 

 Mettler balance to ± 2.5 mg and the wet weight of 

 plankton determined by subtracting the jar 

 weight from the total. Each jar was then dried to 

 constant weight in an oven at 60°C. This 



15-1 



13- 



0^11 



Ct ^ 



7- 





3- 



1- 



^B€, A. W. H. 1973. Studies of zooplankton standing stock in the 

 South Atlantic. Unpubl. final tech. rep. to Natl. Sci. Found., 14 p. 



DIFFERENCE BETWEEN 2 YEAR OLD 

 DISPLACEMENT VOLUME 8 LIVE VOLUME (cc/m^j 



Figure 2.— Distribution of differences between displacement 

 volumes measured 2 yr after preservation and the live 

 displacement volume. The live displacement volumes ranged 

 from 30 to 321 cc (0.57 to 2.53 cc/m^) and the 2-yr values ranged 

 from 38 to 340 cc (0.58-2.40 cc/m'). 



779 



