PLUTONIUM IN THE GREAT LAKES 671 



z; < 



< y 



< 



Major 

 diatom- 

 bloom 



Dominance 

 • green, blue-green — »- 

 algae 



Maximum 



• zooplankton- 



grazing 



Minor 



•diatom 



bloom 



CO a 



uj O 



(- OJ 



< 



cc 

 < — 



X 



< _l 



z < 



Major sediment 

 input from 

 watershed 



In situ formation 

 of calcium carbonate 



Resuspension of 



bottom sediments, 



shore erosion 



O 



< 

 UJ 

 CO 



Winter 

 stratification' 



Spring convectlve 

 mixing period 



Thermal bar- 



Summer 

 stratification' 



Fall convective 

 mixing period 



Isothermal 

 mixing period 



JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. 



MONTH 



Fig. 6 Seasonal processes in Lake Michigan. 



E 



o 



I- 

 < 



cc 



o 



O 0.1 

 o 



o 



H 

 to 



UJ 

 CO 



0.01 



>80 Aim 



1 



1 



1 



1 



JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. 



1973 



Fig. 7 Seasonal dependence of the concentration and size distribution of particulate 

 matter in the surface waters of Lake Michigan (ANL-73-3,40 km west of Grand Haven, 

 MicH.). 



