Seasonal photosynthetic activity of autotrophic picoplankton in Lake Kinneret, Israel |
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| Authors: | Malinsky-Rushansky Nechama Z; Berman T; Dubinsky Z |
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| Institution: | 1Israel Oceanographic and Limnological Research, The Yigal Allon Kinneret Limnological Laboratory PO Box 345, Tiberias, 14102, Israel
2Bar-llan University, Department of Life Sciences Ramat-Gan, Israel |
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| Abstract: | Autotrophic picoplankton populations in Lake Kinneret are composedof picocyanobacteria and picoeukaryotes. Overall, the ratesof photosynthetic carbon fixed by autotrophic picoplankton duringthis study were low (0.01–1.5 mg Cm–3 h–1).The highest chlorophyll photosynthetic activity of the <3µm cell-size fraction was found in spring, when picoeukaryotespredominated and in addition small nanoplankton passed throughthe filters. The maximum cell-specific photosynthetic rate ofcarbon fixation by picocyanobacteria and picoeukaryotes was2.5 and 63 fg C cell–1 h–1, respectively. The highestspecific carbon fixation rate of autotrophic picoplankton was11 µg C µg–1 Chl h–1 The proportionalcontribution of autotrophic picoplankton to total photosynthesisusually increased with depth. Picocyanobacteria collected fromthe dark, anaerobic hypolimnion were viable and capable of activephotosynthesis when incubated at water depths within the euphoticzone. Maximum rates of photosynthesis (Pmax) for picocyanobacteriaranged from 5.4 to 31.4 fg C cell–1 h–1 with thehighest values in hypolimnetic samples exposed to irradiance.Photosynthetic efficiency ( |
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