During the whole year 1999 samples of water have been collected twice each
month in Lake Geneva between Hermance and Copper. Qualitative and quantitat
ive data have been recorded: dry weight, number of phytoplankton organisms
per liter, diversity index, chlorophyll content, turbidity and transparency
. The organisms of the net plankton and the pumped water were listed. The r
esults showing the seasonal changes are discussed and compared to those of
the previous year.