PHYSIOLOGICAL ECOLOGY OF ASCOPHYLLUM-NODOSUM (L) LE JOLIS AND ITS DETACHED ECAD SCORPIOIDES (HORNEMANN) HAUCK (FUCALES, PHAEOPHYTA)

The physiological responses of the fucoid brown alga Ascophyllum nodosum (L.) Le Jolis and its detached ecad scorpioides (Hornemann) Hauck were similar under varying conditions of light intensity, temperature and salinity. The optimal light and temperature requirements were 206 microeinsteins (850 ft-c) and 18 to 21 C. No seasonal differences in light optima were noted; in contrast, winter specimens of both plants showed a plateau of net photosynthesis between 10 to 25 C, versus a conspicuous maximum of 18 to 21 C during the summer. Overall, summer plants showed a higher rate of net photosynthesis than winter specimens. Both Ascophyllum plants exhibited a broad but variable tolerance to salinity, with lowest net photosynthesis at 18%0 and maximum efficiency at 0 to 40%. © 1979, Walter de Gruyter. All rights reserved.