MICROPLANKTON 



SAMPLING 



An operation designed to obtain the smaller, denser 

 microplankton immediately followed each sampling of macro- 

 plankton. The instrument cart was again lowered to the 

 bottom, the pump cleared, and the cart drawn to the surface 

 without stopping. 



During these runs, the pump and hydrophotometer 

 were in constant operation. Depth of sampling was computed 

 from the rate of ascent of the instrument cart and the time- 

 lag necessary for water delivery. Six 8 -ounce bottles were 

 filled with water from approximately the same depths as the 

 macroplankton samples and the organisms were fixed with 

 Lugol's iodine. Microplankton samples for each vertical 

 series were taken in approximately 3 minutes. 



PREPARATION OF SLIDES 



With the exception of the stains used, microconstit- 

 uents were prepared by the technique reported by Holmes 

 (1962).'^* The sample was thoroughly agitated, and a 20-ml 

 aliquot was removed and introduced into a Millipore filter 

 apparatus. The aliquot was drawn through an HA Millipore 

 Filter, pore size 0. 45 micron +0. 02 micron, under pressure 

 of 10 to 11 psi. Salts were removed by passing a series of 

 increasingly dilute seawater-distilled water solutions 

 through the filter membrane. The filter was rinsed with 

 distilled water and stained with a saturated aqueous solution 

 of Safranine "O" for 20 minutes. The sample was dehydrated 

 with increasing concentrations of ethanol in distilled water. 

 Between applications of the 75- and 100-percent solutions 

 of alcohol, the sample was counter-stained with a saturated 

 solution of Light Green in 95-percent ethanol for 5 to 6 

 seconds. The filter was cleared with beechwood creosote 

 and mounted on slides with Canada balsam. For these 

 operations a manifold (fig. 5) was fabricated which permitted 

 the simultaneous preparation of six samples. In practice. 



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