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Distribution, production, and ecophysiology of Picocystis strain ML in Mono Lake, California
ROESLER Collin S. ; CULBERTSON Charles W. ; ETHERIDGE Stacey M. ; ...
A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California, occupies a niche that spans two environments: the upper oxic mixolimnion and the deeper anoxic and highly reducing monimolimnion. This organism, Picocystis sp. strain ML, accounts for nearly 25% of the primary production during the winter bloom and more than 50% at other times of the year. In incubations, it is heavily grazed by the brine shrimp, Artemia monica. We assessed growth and photosynthetic parameters over broad ranges of irradiance, salinity, and pH and under oxic and anoxic conditions. Picocystis appears to be particularly adapted to low irradiance; we observed an order of magnitude increase in the cellular pigment concentrations, as well as marked increases in cell-specific photosynthetic parameters for cells acclimated to low-growth irradiance. Growth rates of 0.3-1.5 d-1 were observed over a salinity range of 0-260%o and a pH range of 4-12, with maximal growth at ∼50 μmol photons m-2 s-1, 40‰, and pH 6-10. Growth and oxygenic photosynthesis were observed under anoxic conditions at rates comparable to those measured under oxic conditions. The ability of the organism to acclimate and grow under such a broad range of environmental conditions makes it an important component of the Mono Lake ecosystem and likely contributes to its dominance of the monimolimnion/mixolimnion interface.
American Society of Limnology and Oceanography
ISSN : 0024-3590 CODEN : LIOCAH
Limnology and oceanography A. 2002, vol. 47, n° 2, pp. 440-452 [bibl. : 1 p.1/4]
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