Seasonal photosynthetic activity of autotrophic picoplankton in Lake Kinneret, Israel

Nechama Z. Malinsky-Rushansky, T. Berman, Z. Dubinsky

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23 Scopus citations


Autotrophic picoplankton populations in Lake Kinneret are composed of picocyanobacteria and picoeukaryotes. Overall, the rates of photosynthetic carbon fixed by autotrophic picoplankton during this study were low (0.01-1.5 mg C m-3 h-1). The highest chlorophyll photosynthetic activity of the <3 μm cell-size fraction was found in spring, when picoeukaryotes predominated and in addition small nanoplankton passed through the filters. The maximum cell-specific photosynthetic rate of carbon fixation by picocyanobacteria and picoeukaryotes was 2.5 and 6.3 fg C cell-1 h-1, respectively. The highest specific carbon fixation rate of autotrophic picoplankton was 11 μg C μg-1 Chl h-1. The proportional contribution of autotrophic picoplankton to total photosynthesis usually increased with depth. Picocyanobacteria collected from the dark, anaerobic hypolimnion were viable and capable of active photosynthesis when incubated at water depths within the euphotic zone. Maximum rates of photosynthesis (P(max)) for picocyanobacteria ranged from 5.4 to 31.4 fg C cell-1 h-1 with the highest values in hypolimnetic samples exposed to irradiance. Photosynthetic efficiency (a) was ~4-fold higher in picocyanobacteria sampled from 40 m than in cells from near-surface waters. Light saturation (I(k)) was lower in picocyanobacteria from 40 m, suggesting that these cells were acclimated to lower light intensities. The relative contribution of autotrophic picoplankton to total phytoplankton photosynthesis in Lake Kinneret was low, but occasionally, at seasons and depths where pico-cyanobacteria or picoeukaryotes were abundant, could account for most of photosynthetic activity.

Original languageEnglish
Pages (from-to)979-993
Number of pages15
JournalJournal of Plankton Research
Issue number8
StatePublished - Aug 1997

Bibliographical note

Funding Information:
The authors wish to thank Dr Y.Z.Yacobi for providing data on phytoplankton photosynthesis, Prof U.Pollingher for useful discussions, and M.Hatab and V.Harel, the crew of the Hermona. This work is in partial fulfilment of N.Z.Malin-sky-Rushansky's requirements for a PhD thesis at Bar-Dan University and was supported by Grant 1932-1-93 from the Ministry of Science and the Arts, Jerusalem, Israel, by a grant (No. 87-00006) from the US-Israel Binational Science Foundation, Jerusalem, Israel and by the Israel Water Commissioner. A contribution of Israel Oceanographic & Limnological Research.


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