compared to 1929> and were outnumbered by greens and by blue-greens 

 on every data. The greens and blue-greens were distinctly more 

 abundant in 1930 than in 1929. One possible reason for these dif- 

 ferences is the difference in temperature in the two years. As 

 mentioned several times before, 1930 was a warmer season than 1929, 

 and presumably would favor the development of greens and blue-greens, 

 and retard the development of diatoms. 



In both years the blue-greens were more abimdant than the 

 greens on most of the dates. The three dates on which this relation 

 was reversed came in the early part of the season. The same was 

 true at Station 25U (Table 58) and (less consistently) at Station 2$0 

 (Table 56), agreeing with the findings in the Island Section, 



Comparing abundance at Stations 250 and 252, it may be seen 

 that the counts were generally higher at Station 252 in 1929, and at 

 Station 250 in 1930, It was pointed out previously that two of the 

 four samples at Station 250 in 1929 were taken when the current was 

 out of the river, whereas only two of the six samples of 1930 were 

 taken at that phase of the current. This would account, in part, for 

 the relatively low counts of 1929 compared (1) to those of 1930 at 

 the same station, and (2) to those of 1929 at Station 252. It seems 

 probable that the abundance of plankton is ordinarily greater in the 

 area about Station 250 than at Station 252, but it is not possible to 

 prove this statement from the available data. 



Station 25U • Station 25U is located well outside of the 

 natural limits of Maumee Bay, and the conditions which prevail here are 

 those of the open lake. The water is 6.2 meters deep. Table 58 shows 

 the data collected here in 1929 and 1930, 



In spite of the short periods of time covered, distinct 

 seasonal trends similar to those in the Island Section are evident. In 

 both seasons the diatoms decreased in the early part of the season, and 

 later increased, reaching the maximum at the end of the season. The 

 greens also declined in the early part of the season and reached their 

 greatest abundance in early September. The early season decline was 

 absent in the blue-greens, but they reached their maximum at the same 

 time as the greens. In the relative abundance of these groups, the 

 situation was similar to that at the preceding station. In 1929 the 

 diatoms generally outnumbered the greens and blue-greens, while in 

 1930 this relationship was reversed. In both years, greens were more 

 abundant than blue-greens in the early part of the season, and less 

 abundant later. In general, the plankton was much more abundant in 

 1930 than in 1929, 



The abundance of phytoplankton at Station 25U was less than at 

 Station 252 on every date except Septenfcer 9, 1930, The superiority 



187 



