the blue-greens and greens, and less so for the diatoms. Perfect cor- 

 relation is not to be expected, even if the sampling program were per- 

 fectly adequate, because of differences in weather conditions in the 

 two years, and because of the diversity of material from which the 

 data were derivedL, 



In view of the close agreement between the two years with 

 regard to (1) average abundance of phytoplankton groups, (2) times of 

 changes in abundance, and (3) degree and direction of change, it seems 

 safe to conclude that the sampling program was adequate for the needs 

 of the investigation. In all probability, none of the conclusions 

 reached in this report would have been changed materially by a more 

 complete coverage of the area studied. 



Abundance of phytoplankton conpared with that 

 of other lakes 



The question of the abundance of phytoplankton in the Island 

 Section of Western Lake Erie as compared with other lakes is one of 

 considerable interest, but the obstacles to direct comparison are great, 

 owing to the diversity of methods and manner of reporting data employed 

 by different investigators. Any answer given to the question at this 

 time must be rather unsatisfactory, but it seems worthwhile to draw a 

 few comparisons. These comparisons will be made on the basis of the 

 amount of plankton per unit of volume of water, rather than the amount 

 per unit of surface. In general, deep and shallow lakes of the same 

 surface area, and situated in similar regions, produce about the same 

 total amount of plankton; in the shallow lakes it is more concentrated 

 than in the deep ones. From the standpoint of availability to plankton- 

 feeding fishes, it is more important to know the concentration of the 

 organisms than the total number present in the lake. 



Before taking up a comparison of the Island Section of Western 

 Lake Erie with other lakes, it may be well to compare abundance in this 

 part of the lake with the part to the east, Burkholder (1929a) reported 

 counts at several stations east of Point Pelee in parts of July, August, 

 and September, 1928. The data indicate extreme rarity of phytoplankton 

 as compared with Western Lake Erie, Diatoms were much more abundant 

 than greens or blue-greens, but even in Septenber, when diatoms were 

 most abundant, no station had a count as high as S thousand units per 

 liter. 



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