Actinastrum hantzschii, Chlorophyta, Chlorococcales. Usually found in single star-like colonies, not in a bundle of colonies as seen in this photo.
This species was abundant in the lake plankton in the 1980s and early 1990s but occurs only rarely in recent years, appearing mostly in summer and more often in the littoral.
aalster and tzohary
A Alster & T Zohary, Kinneret Limnological Laboratory, IOLR
Photo taken with an Olympus BX50 Microscope equipped with DIC optics and PixeLink digital camera, mag. X40