UTILIZATION OF SOLAR ENERGY BY AQTATIC ORGANISMS 



33 



PERCENTAGE OF SURFACE LIGHT 



0001 



001 







1.0 



10 



00 

 



o 

 m 



8 







m 



H 



m 

 (/) 



Fig. 6. Comparison of rates of penetration of three regions of the spectrum into Midge Lake. The 

 curves represent average values of the extinction coefficients as measured by Birge and Juday (1930). 



separate consideration will be given to the 

 major subdivisions of the solar spectrum to 

 which the followin<i' magnitudes may be 

 roughly assigned : Infrared, 41 per cent ; 

 ultraviolet, 7 per cent; and visible, 52 per 

 cent. As shown bv Fig. 2. the infrared 



radiation is almost entirely absorbed in the 

 uppermost meter. The chief importance of 

 the infrared is, therefore, the rapid heating 

 of the surface stratum. 



Ultraviolet light in large amounts is in- 

 jurious to plankton and other organisms, 



UV V 



WAVELENGTH 

 Fig. 7. Crystal Lake, Wisconsin. The spectral 

 distribution of solar energy as it reaches the sur- 

 face of the lake is given by the uppermost curve. 

 The reduction in intensity and the changes in spec- 

 tral distribution at successive depths in the lake are 

 indicated by the curves beneath (from Birge and 



James 1939). 



UV V 



B 



G Y 



R 



WAVELENGTH 



Fig. 8. Eudolph Lake, Wisconsin. The spectral 

 distribution of solar energy as it reaches the lake 's 

 surface is given by the uppermost curve. The 

 reduction in intensity and the changes in sjiectral 

 distribution at successive depths in the lake are 

 indicated by the curves beneath (from Birge and 

 James 1939). 



