Seasonal dynamics of picophytoplankton in Lake Kinneret, Israel

Abstract

1. Picophytoplankton (picocyanobacteria and picoeukaryotes) commuruties in Lake Kinneret were studied from 1988 to 1992. No prochlorophytes were observed in the lake. 2. Picocyanobacteria were a prominent and ubiquitous component of the phytoplankton, being present at all depths throughout the year, with concentrations ranging from 2 X 10-8 X 10^ cells n:il"^ Low cell numbers in winter and spring were followed at the end of the annual dinoflagellate bloom by maximal abundances in summer-autumn in the epilimnion. High cell numbers (> l O"* cells ml'' ) were sometimes also found in the anaerobic hypolimnion. Net growth rates for picocyanobacteria ranged from 0.29 to 0.60 divisions day''. 3. Picoeukaryotes were a very minor constituent of the picoplankton, mostly present in winter and spring, and sometimes at the end of autumn, with concentrations ranging from 44 to 5700 cells ml'^. Higher cell numbers tended to occur in the near surface water layers, hi August-September, picoeukaryotes were found only in the hypolimnion. In December, the occurrence of picoeukaryotes in the deep water layers probably resulted from advection with cold water currents from the Jordan river. Net growth rates for picoeukaryotes ranged from 0.26 to 0.43 divisions day'. 4. Overall, the contribution of picophytoplankton to the phytoplankton standing crop in Lake Kinneret was limited; picocyanobacteria and picoeukaryotes accounted for no more than 7.0 and 0.1% of total algal biomass (semiannual average), respectively. 5. Picophytoplankton cell numbers in pelagic waters were usually similar to those in shallower lake stations. 6. Ficocyanobacteria appear to be an autochthonous population, whereas picoeukaryotes are probably brought annually by the Jordan River and do not maintain themselves in the lake.

Genetic diversity of cyanobacterial communities in Lake Kinneret (Israel) using 16S rRNA gene, psbA and ntcA sequence analyses

“…Picocyanobacteria of the Synechococcus type have been recorded in Lake Kinneret in a long-term study (Malinsky-Rushansky et al 1995). Synechococcus is a 238 Fig.…”

“…Another group common in the historical records, Microcystis sp., appears in some years with relatively high abundances at the beginning and/or the end of winter and is correlated with changes in the annual bloom of Peridinium gatunense (Sukenik et al 2002). Picocyanobacteria, unicellular cyanobacteria with sizes ranging from 0.2 to 2 µm (Callieri & Stockner 2002), are also a prominent component of the phytoplankton in Lake Kinneret (Malinsky-Rushansky et al 1995). Microscopic observations during a period of 4 yr showed that the annual and vertical distribution of picocyanobacteria is correlated with temperature and light, and that this group appears at all depths throughout the year, with maximal abundances in late summer into early autumn in the epilimnion (Malinsky-Rushansky et al 1995.…”

“…Picocyanobacteria, unicellular cyanobacteria with sizes ranging from 0.2 to 2 µm (Callieri & Stockner 2002), are also a prominent component of the phytoplankton in Lake Kinneret (Malinsky-Rushansky et al 1995). Microscopic observations during a period of 4 yr showed that the annual and vertical distribution of picocyanobacteria is correlated with temperature and light, and that this group appears at all depths throughout the year, with maximal abundances in late summer into early autumn in the epilimnion (Malinsky-Rushansky et al 1995. Two of these picocyanobacteria, Synechococcus and Prochlorococcus, dominate the photoautotrophic picoplankton over vast areas in the oceans, having a great importance for global primary production (Partensky et al 1999, Scanlan & West 2002.…”

Seasonal abundance and vertical distribution of Protozoa (flagellates, ciliates), and bacteria in Lake Kinneret, Israel

“…At this time, herbivorous cladocera (Cenodaphnia reticulata, Diaphanosoma brachyurum, Bosmina longirostris) dominated the zooplankton. Phytoplanktonic primary production during winter-spring in 1989 and 1990 averaged -2.0 g C m-2 d-' (Berman et al 1995) and was due mainly to Pendinium. Since dinoflagellates are not directly grazed by cladocera there appeared to be a shortfall in algal sources to supply the carbon demand of the herbivorous zooplankton (Serruya et al 1980).…”

“…Maximum phytoplankton abundance reaches -250 g m-' (wet weight biomass) or -300 mg m-2 (chlorophyll) and primary production -2.5 g C m-2 d-' (Berman et al 1995). Most of the dominant Peridinium biomass is not grazed by metazoan zooplankton (Serruya et al 1980).…”