40 



LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



standard units (8,000 cu. micra) , shows an increasing quantity above Mill 

 Dam. Following introduction of mill wastes, the quantity drops within 

 1.5 miles from 190 to 95 volumetric standard units. Plankton again increase 

 in the quiescent water behind Pixley and Crowley Dams although never 

 reaching the volume peak above Mill Dam. The decrease from the 11 mile 

 level downstream shows the destructive and inhibitory influence of swift 

 and turbulent water. If quiescent water persisted downstream, it is possi- 

 ble that the plankton volume would increase beyond the peak at Mill Dam. 

 Volume of zooplankton is erratic but shows the same depression as 

 total plankton. As a group, they appear relatively scarce which may be 

 due, in part, to the difficulty of recognition in the preserved condition. These 



CblersfbrMu 



totals, however, do not include immense populations of Carchesium and 

 Vorticella attached to waving masses of Sphaerotilus natans along the 

 shore. 



The main constituents of the phytoplankton show a trend of the same 

 pattern as that of total volume (Graph 4). The green and blue-green algae 

 and the diatoms all show a decline within l^ mile of the pollutant entry 

 point. Volume recovery is rapid from the 3 to 11 mile levels for both green 

 and blue-green algae, whereas the diatoms continue to decline to the 10 

 mile level and then increase only slightly. 



The plankton data fail to locate a point or zone where recovery is 

 complete. It is concluded that the decreases in plankton in the down- 

 stream vicinity of Park Falls reflect the toxic influence of industrial eflBu- 

 ents — perhaps from SO, in waste sulphite liquor. The following rising 



