ABSOLUTE IVIAXIMUM RATE 



995 



and especially of red, algae is the result of chromatic adaptation to the 

 predominantly bluish-green light that prevails deep under the sea; Berth- 

 old (in 1882) and Oltmanns (in 1905), on the other hand, thought that 

 colored algae are adapted not so much to the spectral composition of light 

 in their natural habitats as to its loiv intensity. The ensuing controversy — 

 which led to almost complete vindication of Engelmann's theory of chro- 

 matic adaptation — will be discussed in chapter 30. However, the funda- 

 mental importance of chromatic adaptation for the composition of the 

 pigment system of deep-sea algae does not mean that these algae are not also 

 adapted to low light intensity and do not use the same mechanism — shifts 

 in relative concentrations of red, blue and green pigments — for chromatic 

 as well as for intensity adaptation (c/. Harder 1923). 



6000 



5000 



Cladophora rupeslris, green 



Fucus vesiculatus, brown 

 Ys ~^^hodymenia palmato, red 



\ .^ 



60 75 117 140 



S/90 LIGHT INTENSITY 



197 

 S/2 



Fig. 28.19. Typical light curves of red, brown and green algae 

 (after Montfort 1929). Light intensity in relative units and frac- 

 tions of full sunlight. Equal fresh weights of algae used. 



The response of colored algae from different depths to intense illumination has been 

 studied, among others, by Maucha (1924, 1927), IMarshall and Orr (1927, 1928), Ehrke 

 (1931), Curtis and Juday (1937) and particularly by Montfort (1929, 1930, 1933, i.^ 

 1934, 1936). Figure 28.19 shows a typical "optimum" curve, obtained by the last- 

 named investigator. Montfort noticed that algae from one and the same level often 

 show different resistance to strong light: Some red algae, containing much phycocyanin 

 (such as Rhodymenia palmata), continued to synthesize effectively on the surface, while 

 others, found in the same depth, but containing mainly phycoerythrin (such as Dehsseria 

 alata) suffered a "sunstroke" and died. The surface-living, almost pure-green form of 



