In mid-August 1994, perceptible numbers of Aphanizomenon ovalisporum
Forti filaments began to appear in the lake. By early October, A.ovalisporum
dominated the phytoplankton, reaching a chlorophyll concentration of -20 u.g I"1
and constituting 88% of the total biomass. The bloom declined in late October,
and by mid-November no filaments remained in the epilimnetic water.
This event was the first time that A.ovalisporum had been recorded in Lake
Kinneret since systematic monitoring began in 1967. It marked the first appearance
of a potentially toxic, nitrogen-fixing cyanobacterium in large numbers
during the summer-fall season, a time of year when phytoplankton standing
stocks are generally low and water utilization demands are greatest. In 1995,
A.ovalisporum reappeared in July and persisted until December, but did not
develop a bloom