as much as possible like the sub-littoral of iVestern Lake Erie, In 

 Lake Wawasee, and to a lesser extent in Lake Mendota, the lower parts 

 of the zones selected lie below the thermocline, and are subject to 

 oxygpn depletion durint; the summer. The zones selected in the other 

 lakes lie entirely within a region of high oxygen content, and thus 

 have conditions more like those in V/estern Lake Erie, 



In Table 86 the lakes are listed in order according to the 

 weight of organisms per unit of area, with Wawasee first, Mendota 

 second, Western Lake Erie third, and Green, Simcoe, and Nipigon 

 following in the order named. Lake Wawasee supports by far the 

 largest crop of bottom organisms. Lake Mendota and the Island 

 Section of "Western Lake Erie are nearly the same in this respect, but 

 it is almost certain that, if records from the latter were available 

 for an entire year, it would hold second place in the list. Green, 

 Simcoe, and Nipigon, particularly the last two, are relatively poor 

 lakes. It is evident from the figures given that the Island Section 

 of Western Lake Erie compares favorably with North American inland 

 lakes with respect to the weight of bottom organisms per unit of area. 



Portage River Section 



Samples were taken at only one station in this section. This 

 was Station l59, located one-fourth mile north of the mouth of the 

 river. The bottom is composed of sand with a slight admixture of mud. 

 Fourteen samples were taken here in 1929* and seven in 1930. Very few 

 organisms were found at any time. In 1929 there was an average of 19 

 tubificid worms and 18 chironomids per square meter. No Hcxagenia were 

 found in 1929> but a few specimens were obtained on a single date in 

 1930, Their rarity is readily explained by the fact that the bottom 

 material is almost wholly sand. Tubi fields did not appear in the samples 

 of 1930. It seems probable that waves and currents tend to prevent the 

 deposition of any organic debris which may be discharged from the river. 

 At least there was very little of such material on the bottom, and the 

 biological data give no evidence of pollution, 



Maumee Bay Section 



Regular Stations 



In the Maumee Bay Section there are a number of special con- 

 ditions which determine the type of organisms to be found in the 

 bottom deposits, Maumee Bay itself is somewhat enclosed, and is protected 



267 



