Richard G. Petersen Cecily C.Y. Chang 1995 <p><span>Water samples were collected from Lake Tahoe at midlake and nearshore stations at three depths (25, 50, and 75 m, corresponding to light intensities of approximately 10, 1, and 0.1% of surface light) in May and September. The water samples were evaluated to decide the following: (1) whether carbon fixation was N-limited and whether there were differences between picoplankton and larger phytoplankters and (2) the relative importance of picoplankton carbon fixation and related photosynthetic parameters. Evidence of N-limitation was observed only in September at the midlake station for the populations at 50 and 75 m, and to a lesser extent at the nearshore station at 75 m, but only for the nanoplankton fraction. The contribution of picoplankton to total carbon fixation ranged from 34 to 69% and did not increase with depth. Low values for&nbsp;</span><i>I</i>_k<span>, the photoadaptation parameter, for deep water populations (0.1% light level) in September, but not May, suggested that these populations were adapted to low light in the fall but not the spring.</span></p> application/pdf 10.1139/f95-005 en Canadian Science Publishing Evidence of autumn nitrogen limitation and contribution of picoplankton to carbon fixation in Lake Tahoe article