84 



ECOLOGY 



Part II 



MIDSUMMER TEMPERATURE 

 A TYPICAL DEEP LAKE OF A TEMPERATE ZONE 



Water surface 



(Ti.e'F) 



2 re 



(69.8''F) 



io'c 



(SCF) 



Epilimnion 

 29 Ft. 



Wind-stirred, air- 

 mixed water. 

 Plenty of light. 

 Abundant plankton 



Thermocline 



Transition area, 65% 

 fall in temperature here. 



45 Ft. 



Hypolimnion 



S-S^C .1 128 Ft. 



Bottom 



Still water. 

 Little or no light. 

 Maximum range of 

 temperature for year 

 about 40° F. 



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B 



69.0°F 

 SO.O'F 



41. CF 



SUMMER 

 Layers as in A Wind blows 

 surface waters. Temperature 

 shift in thermocline. 



v/yy/y/A .ce ^// ////////a 32.2" f 



37.2° F 

 39.2° F 



TrWTTy^TTr' 39. 2 F 



WINTER 

 Ice cover is a boon to population 

 beneath it. Plankton sinks with 

 heavy water. 



39.2° F 



•::':y^^T?.Ui.i.i!.t|ii|giii 



39.2° F 



39. 2° F 



AUTUMN OVERTURN 

 Cold winds blow and chill surface 

 waters. Their temperature changes 

 fo 39.2° F. They fall and mix. 



" ^ if ' "' ic ' '' '' ^j/^ 



39. 2° F 



39. 2° F 

 39. 2° F 



39. 2° F 



SPRING OVERTURN 

 Ice melts. Surface water changes 

 to 39.2°F, IS heavier and falls, 

 mixes ond displaces lower waters. 

 Stir brings plankton to surface. 



