30 



PROBLEMS OP LAKE BIOLOGY 



Curve 



Location 



Authority 



1 

 2 

 3 



4 



6 

 7 

 8 

 9 

 10 



11 



12 

 13 

 14 



Midge Lake, Wisconsin 



Trout Lake, Wisconsin 



Gunflint Lake, Minnesota 



Woods Hole Harbor 



f Thatcher Pass, San Juan 



•| Islands 



[ Buzzards Bay 



Vineyard Sound 



Baltic Sea 



Crystal Lake, Wisconsin 



English Channel 



Gulf of Maine (deep basin) 



f Off Vancouver Island 



■{ Continental Slope, s. of Nan- 

 [ tucket Shoals 



Gulf Stream 



Cayman Sea (Caribbean) 



Distilled water 



Birge and Juday (1930) Fig. 15 



li a ii << pjg_ 24 



Erikson (1933) at 5450A 



Oster and Clarke (1935) Scr. 316 



Utterbaek and Jorgenson (1934) at 5300 A 

 Oster and Clarke (1935) Ser. 325 

 " " " " Ser. 322 



Pettersson and Landberg (1934) Fig. 2 

 Birge and Juday (1930) Fig. 14 

 Atkins and Poole (1933) Ser. 58 

 Oster and Clarke (1935) Ser. 301 

 Utterbaek and Jorgenson (1934) at 5300A 



Oster and Clarke (1935) Ser. 314 

 " " " " Ser. 311 



Clarke (1938b) Ser. 438 

 James and Birge (1938) at 5460a 



material present have a selective action on 

 light beyond that of the water itself, and 

 the nature of the selective effect varies 

 widely from one body of water to another. 

 As a result it becomes necessary to measure 

 separately the rate of penetration of each 

 spectral region for each lake or oceanic 

 area. Four typical cases are presented to 

 illustrate the very great differences which 

 are encountered in the selective action of 

 natural waters. 



In the Sargasso Sea (Pig. 4) the red part 

 of the spectrum is absorbed at the most 

 rapid rate, the yellow-green and violet com- 

 ponents are reduced much more slowly, and 

 the blue light penetrates the most effec- 

 tively. The theoretical maximum for the 

 transparency of any natural water is indi- 

 cated in the figure by the distilled water 

 curves for (1) the wavelength at which 

 absorption is least (4730A, k = 0.005) and 

 (2) for the average of a band extending 

 500a each side of this (av. k = 0.010) . Sea 

 water as transparent as the latter has 

 actually been observed for limited strata 

 in the Sargasso Sea (Clarke 1933). In 

 Vineyard Sound (Fig. 5) the red compo- 

 nent of sunlight is similarly absorbed more 

 rapidly than any other, but here the yellow- 

 green component is by far the most penetra- 

 ting, and the blue and violet regions take an 

 intermediate position. The same situation 

 obtains in the clearest lakes as, for example, 



in Crystal Lake. In Trout Lake, however, 

 although the yellow-green component still 

 penetrates the most effectively, blue light 

 is absorbed a little more rapidly than the 

 red (Fig. 5). In the ease of a highly 

 colored lake like Midge Lake the relative 

 rates of absorption are just the reverse of 

 those in very clear water, for here we find 

 that red light is the most penetrating and 

 blue the least with yellow in an intermedi- 

 ate position (Fig. 6). 



The changes in the distribution of the 

 solar energy at increasing depths which re- 

 sult from the differences in the selective ac- 

 tion of the foregoing types of water are 

 very pronounced. The situation in the Sar- 

 gasso Sea is qualitatively similar to that 

 which would occur in distilled water (Fig. 

 2). The energy distribution at various 

 levels in Crystal Lake will serve as an 

 example for the clearest inland waters or 

 for most coastal waters (Fig. 7). Kudolph 

 Lake has been taken as an illustration of a 

 liighly colored lake (Pig. 8). One observes 

 that whereas in the clearest water blue light 

 remains after the other parts of the spec- 

 trum have been removed, in the case of 

 Crystal Lake the energy present at 15 

 meters consists almost entirely of yellow 

 and green light, and in Rudolph Lake at 5 

 meters the energy is practically confined to 

 the red and orange regions. 



In the foregoing cases it has been 



