455 



is the unique factor which more than any other differentiates 

 it from lake plankton. To a less degree it seems to differentiate 

 this aquatic environment from other streams, as a result 

 largely of the imperfectly developed flood-plain, and conse- 

 quent unusual proportion of reservoir backwaters. 



It is, moreover, an exceedingly variable factor, operating 

 with almost constant change in each locality, and from season 

 to season in the same locality. It is this element of fluctuation 

 and the resulting chaos in the movements of production which 

 particularly characterize the river as a unit of environment, 

 and in a large measure differentiate it from the more stable 

 lake. The changes depend primarily upon the unequal distri- 

 bution of the rainfall and its run-off and the consequent fluctu- 

 ations in levels with attendant changes in area, depth, condi- 

 tions of ingress and egress of water in any given area, current, 

 and age of the water. 



The effect of the area of the body of water upon its plank- 

 ton production in our situation is so masked by combination 

 with other factors that the available data are inconclusive. 

 Our largest vegetation-poor backwater, Thompson's Lake, pro- 

 duces less (8.26 cm. 3 ) than the smaller one, Phelps Lake (22.35 

 cm. 3 ). On the other hand, the largest vegetation-rich area, Flag 

 Lake, produces 9.23 cm. 3 — considerably more than the smaller 

 Quiver and Dogfish lakes, 1.75 and 3.16 cm. 3 — and these differ- 

 ences are, moreover, in all probability to be attributed to other 

 factors than mere area. 



The relative development of the shore-line is a corollary of 

 the form of the body of the water, and is thus related to its 

 area. In the case of the river, the development of the shore- 

 line, as shown on page 284, is 78.3 — a disproportionately large 

 element in the environment of the plankton. 



This factor of area has been introduced here in order to 

 emphasize the fact that mere size in itself has apparently little 

 to do with plankton production. Plankton is present in small 

 as well as large bodies of water, with, of course, an increasing 

 proportion of littoral influences as areas contract. Within 



