Estimates of the aaount of organic matter in Lakes Canandaigua, 

 Cayuga, and Seneca, in summer (Birge and Juday, 1921, page 250), 

 indicate that these lakes are much poorer in plankton than 

 Green Lake. 



It is clear that the abundance of plankton per unit of 

 volume in Western Lake Erie is between that of Lake Mendota, a 

 eutrophic lake, and Green Lake, an oligotrophic laJce, These two 

 lakes are fairly typical of their classes; the first class is generally 

 rich in plankton, (per unit of volume) and the second generally poor 

 (Thienemann, 1925, page 202), It is a question Just what position to 

 assign to the Island Section of Western Lake Erie in the wide range 

 between the rich and poor lakes, but it probably stands nearer the 

 rich end of the scale, and might be described as "moderately rich" in 

 plankton. It has been shown that the main part of Lake Erie contains 

 considerably less plankton per unit volume than the Island Section, 

 The lake as a whole, then, would stand below the Island Section in the 

 scale of richness. 



In making these comparisons, only the Island Section has been 

 considered. It will be shown later that there are pronounced irregular- 

 ities in horizontal distribution in V/estern Lake Erie as a whole, and 

 the available data do not permit a determination of the mean abundance 

 for the whole area. The southwest corner of the lake is rich in plank- 

 ton and the northwest corner is poor, as compared with the Island 

 Section, so that the latter probably is fairly representative of the 

 whole. 



Portage River Section 



rnls section of the lake was represented by a single regular 

 station (Station 1^9), located l/U mile out from the mouth of Portage 

 River. Because of littoral currents, and the alternate inflow and outflow 

 of the river, conditions at this point are constantly changing. In order 

 to determine the changes in the abundance of phyto plankton, it would be 

 necessary to make a special investigation of this small area. In the 

 present study, it was possible to take samples only a few times during 

 the season, and the records are necessarily inadequate. However, they 

 are sufficient to indicate some well-marked differences between this 

 section and the open water of the Island Section. The figures on abundance 

 of the phytoplankton groups for 1929 and 1930 are given in Table 55. 



179 



