THE PREPARATION OF MARINE PHYTOPLANKTON 

 FOR MICROSCOPIC EXAMINATION AND 

 ENUMERATION ON MOLECULAR FILTERS^ 



by 



Robert W, Holmes 

 Associate Research Biologist 

 Scripps Institution of Oceanography- 

 University of California 

 La JoUa, California 



ABSTRACT 



The use of the molecular filter in the preparation of marine phytoplankton for 

 microscopic examination and enumeration is discussed, and certain modifications 

 in the method of Goldberg, Baker, and Fox (1952) are suggested. 



The modified technique involves the filtration of a fixed and preserved sea- 

 water sample. The organisms, retained on the upper surface of the filter, are 

 washed with successively diluted volumes of sea-water, dehydrated with ethanol, 

 stained with alcoholic Fast Green, and finally rinsed with absolute ethanol. The 

 filter disk is cleared with beechwood creosote, xylene, or anisole and mounted di- 

 rectly on a microscope slide with xylene or toluene balsam under a thin cover 

 glass. 



Many nannoplankton species may be readily identified and counted on the filter 

 disk. The method is quantitatively comparable to the Utermohl technique. The dis- 

 tribution of organisms on the filter surface is nonrandom, and the organisms on the 

 entire filter should be counted. 



INTRODUCTION 



Goldberg, Baker, and Fox (1952) described 

 a method of preparing marine phytoplankton 

 for microscopic examination and enumeration 

 directly on molecular filters. While similar 

 membrane filters (wet-type) have been em- 



^Support for this research was provided by the Ma- 

 rine Life Research Program of the California Coopera- 

 tive Oceanic Fisheries Investigations and the Scripps 

 Tuna Oceanographic Research program, financed by 

 the U,S. Bureau of Commercial Fisheries under Con- 

 tract No. 14-19-008-9354 with funds available under the 

 Act of July 1, 1954 (68 Stat. 376). commonly known as 

 the Saltonstall- Kennedy Act. 



ployed for such purposes by German 

 limnologists (Utermohl, 1931; Heinrich, 1934; 

 and Schmitz, 1950), Goldberg, Baker, and Fox 

 (1952) apparently were the first to employ 

 similar techniques utilizing the new dry-type 

 molecular filters. 



On the basis of extensive experience with 

 the method of Goldberg, Baker, and Fox 

 (1952), we have adopted modifications in the 

 technique which reduce the time required for 

 making the individual preparations and pro- 

 vide preparations which are optically superior. 

 The responses of a variety of organisms to 

 the treatment have been examined, and the 



