LIGHT-DEPENDENT GROWTH, DARK SURVIVAL, AND GLUCOSE UPTAKE BY CRYPTOPHYTES ISOLATED FROM A FRESHWATER CHEMOCLINE.

Clones of Cryptomonas phaseolus Skuja, Cryptonuonas rostratiformis (Skuja) Skuja in Hubber-Pestalozzi, and Cryptomonas undulata Gervais were isolated from the deep chlorophyll maximum near the oxu/anoxic boundary layer of the mesoeutrophic lake Schlachtensee, Germany Different autecological features of these species were studied in batch culture experiments. Cryptomonas cf. ovata Ehvenberg and Chroomonas sp. That never dominated in the deep chlorophyll layer were also isolated from Schlachtensee to study their light-dependent growth in comparison to the deep-living species. Cryptomonas undulata. C. cf. ovata, and C. Phaseolus had a very low light compensation point (5-7 μ mol-m[sup-2]-s[sup-1]), whereas the growth rate of Chroomonas sp. and C. rostratiformis was positive above 16 and 24 μ mol-m[sup-2]-s[sup-1], Cryptomonas phaseolus and Chroomonas sp. Became photoinhibited above photon flux densities of 92 and 116 μ mol-m[sup-2]-s[sup-1], Cryptomonas rostratiformis, C. cf. ovata, and C. undulata reached a maximum growth rate at a considerably higher photon flux density (198-250 μ mol-m[sup-2]-s[sup-1]). Cryptomonas phaseolus grew fastest under light-limiting conditions. Cryptpmonas phaseolus and C. undulata were best able to survive prolonged periods of darkness, Cryptomonas phaseolus, C. Rostratiformis, and C. undulata did not show any uptake of fluorescent latex beads. When labeled glucose was provided in naturally occurring concentrations, carbon uptake by C. phaseolus, C. rostratiformis, and C undulata was negligibly small in comparison to cellular carbon content. I suggest that the adaption to a low-light environment is an important preadaption for the dominance of C. phaseolus and C. undulata near the freshwater chemocline. [ABSTRACT FROM AUTHOR]