A SURVEY OF THE MICROPLANKTON 

 OF LAKE ERIE 



Paul R. Burkholder, Microplanktonologist 

 Cornell University 



CONTENTS 



Page 



Introduction 123 



Methods 123 



The species of microplankton 124 



I sokontae 124 



Heterokontae 125 



Chrysophyceae 125 



Bacillariales 125 



Dinophyceae 126 



Eugleninea e 126 



Myxophyceae 126 



Protozoa 127 



R otifera 127 



Distribution and seasonal variation of major 



microplankton groups 128 



Vertical distribution 128 



Horizontal distribution 128 



Seasonal variation 131 



Microplankton communities 137 



INTRODUCTION 



In a commercial fisheries investigation such as 

 that under consideration in Lake Erie, the determin- 

 ation of the kinds and quantity of fish food and the 

 conditions for its production are very important as- 

 pects of the general problem. When limnological 

 investigations were initiated on the western end of 

 Lake Erie more than thirty years ago (H. M. Smith 

 1898, J.E. Reighard 1893) considerable attention 

 was devoted to studies of the micro -fauna and flora 

 of the regional waters. A number of valuable sci- 

 entific contributions (Jennings 1900, Pieters 1902, 

 Snow 1903) to our knowledge of the plankton re- 

 sulted from those early efforts. In view of the basic 

 nature of microplankton in the economy of the lake, 

 quantitative and qualitative analyses are of prac- 

 tical significance and were included in the general 

 survey of the lake in the summers of 1928 and 1929. 



Those methods of investigation employed in 

 the survey of the eastern end of the lake during the 

 summer of 1928 were resumed on a larger scale in 



the season of 1929 so as to include practically the 

 entire lake with the exception of the extreme west- 

 ern end. On each of the four biological cruises, 

 executed with the U. S. Fisheries Steamer Shear- 

 water, during the months of June, July, August, and 

 September 1929, the plankton samples were obtained 

 from some 55 different stations established at selected 

 points throughout the entire lake (fig. 1), for the pur- 

 pose of determining the seasonal, vertical, and hori- 

 zontal distribution of the constituent species. Tow- 

 net gatherings were made also at a number of points 

 along the shore, especially during the month of 

 August, for the purpose of comparing the marginal 

 areas with the limnetic. 



METHODS 



Qualitative samples were obtained at each sta- 

 tion by towing a No. 20 silk bolting cloth net, 1 foot 

 in diameter, for 5 minutes at the surface. These 

 samples were preserved with formaldehyde and used 

 in the laboratory for purposes of identification and as 

 a supplement to the quantitative sampling. 



For quantitative purposes, collections of micro- 

 plankton were obtained by the following method: At 

 each station samples of water were taken from the 

 surface and bottom by means of a Gould hand pump 

 and rubber hose. Fifty liters were measured into a 

 galvanized iron can and then strained through a No. 

 20 silk net with attached bucket. The organisms re- 

 tained in the bucket were washed into a 4 -ounce bot- 

 tle and sufficient formaldehyde added to preserve. 



For the purpose of recovering any organisms which 

 were so small as to go through the No. 20 silk strainer, 

 l-Uter samples of water were also taken from the sur- 

 face and bottom. These samples were preserved with 

 formaldehyde in glass fruit jars until they could be 

 centrifuged. 



In the laboratory, samples which had been 

 strained from the 50-Liter water samples were all 

 concentrated to a standard volume of 20 cc. and pre- 

 served in vials for counting. The l-Uter samples of 

 water were run at uniform speed through a Foerst cen- 

 trifuge and the recovered organisms made up to a 

 standard suspension of 10 cc. 



Enumeration of the phytoplankton was accomplished 

 by the standard random count method. The rotifers 



123 



