1. Lake Kinneret is a warm (13-30 degrees C) monomictic lake. Between
January and June a heavy annual bloom of the dinoflagellate Peridinium
gatunense dominates phytoplankton biomass (250 g m(-2)). At the begin
ning of the summer, degradation and decomposition of the Peridinium bi
omass occurs, serving as a trigger for intense sulphate reduction in t
he hypolimnion and sediments. 2. The rates of sulphate reduction in th
e sediments varied seasonally from 12 to 1700 nmol SO4-2 reduced cm(-3
)day(-1) in December and July, respectively. The availability of organ
ic matter and sulphate is high in June after the crash of the Peridini
um bloom and the beginning of stratification and is lowest in December
before overturn. 3. Sulphate concentrations in the hypolimnion range
between 0.52 mM and 0.20 mM during mixing (January-April) and before o
verturn (December), respectively. The depletion in sulphate in the hyp
olimnion is stoichiometrically correlated to the increase in sulphide.
The lake is not depleted of sulphate at any time, so the sulphate red
uction process in Lake Kinneret is not limited by sulphate concentrati
ons except in the sediments just before overturn.