phosphorus fraction in examined lake ecosystems (Fig.
2A, Table 1). The highest hydrolysis activity of acetate
esterase from measured extracellular enzyme activities
(Fig. 2, 3 and 4A) might be in correlation with the
presence of broad substrate spectrum of acetate
esterase in the lake ecosystems. The reason for
significantly higher acetate esterase activities in
October than in June at all localities, except for Provala
(p < 0.001) (Fig. 3A), could be the presence of high
level of surfactants in October (Table 1). SUR matters
could affect microbial growth by increasing
bioavilability of hydrophobic compounds and
accelerating their degradation (Bardi et al., 2000). The
highest hydrolytic activity of acetate esterase in Palic
and Ludas 1 in October was in correlation with TOC
levels in water ecosystems. Significantly higher
specific enzyme activities (p < 0.001) in October than
in June (Table 2), among the other factors, could be
related to the effect of temperature on enzyme synthesis
and activity. This complies with the well known fact
that low water temperature could induce greater enzyme
production by certain bacteria (Quist and Stokes, 1969).