A LIMNOLOGICAL RECONNAISSANCE 



51 



upper strata. Attention may be called to the fact here 

 that this form has also been found in the lower water of 

 much deeper lakes, such, for example, as Seneca lake. New 

 York, which has a maximum depth of 188.4 m. (618 ft.). 



TABLE 25 — Analysis of the nannoplankton. The figures given in 

 this table indicate the number of individuals per liter of 

 water. 

 The following abbreviations have been used: 

 Protozoa, C^Cryptomonas, B.=Halteria, M^Monas, P=Pandorina, 

 \=^Vorticella; Algae, A^=Aphanocapsa, 0=Oocystis. 



For obtaining the weight of the nannoplankton a com- 

 posite sample was prepared by mixing equal volumes of 

 water from each 5 m. level of the lake. The dry organic 

 matter in the material obtained from this sample amounted 

 to 333.0 mg. per cubic meter of water. This amount plus 

 that in the net planlcton (193.2 mg.) gives 526.2 mg. per 

 cubic meter of water for the total plankton ; approximately 

 63% of this total is derived from the nannoplankton and 

 37% from the net plankton. This sum multiplied by the 

 maximum depth of the lake, that is, 40.2, gives 21,153 mg., 

 or 21.1 grams, per square meter of surface in the deepest 

 water. 



Assuming that this plankton material was uniformly dis- 

 tributed over the whole lake, then the average per square 

 meter of surface for the entire lake may be obtained by 

 multiplying the sum of the net plankton and nannoplankton 

 by the mean depth, namely, 12.3 (See table 2). This gives 

 6,472 mg., or about 6.5 grams per square meter of surface. 

 Again assuming a uniform distribution, the dry organic 



