The vertical changes (upper layer: 0~0.5 m, middle layer: 4~5 m and lower layer:
8~10 m) of the limnological variables, zooplankton dynamics and community filtration rate on
the phytoplankton were evaluated monthly intervals from November 2004 to June 2007 at the artificial
lake (Okjeong Lake). During the study, the annual mean of water temperatures were 15.2±
7.8�C (upper layer), 14.5±7.4�C (middle layer) and 13.0±6.2�C (lower layer), respectively (n=
30). The vertical variations of most limnological parameters (DO, pH, conductivity and turbidity)
were fairly similar, except for chl.-a concentration. Annual mean of chl.-a concentration was
highest at the upper layer (21.4 μg L-1), while annual means of concentrations were low at the
middle layer and lower layer (4.3 μgL-1 and 3.5 μgL-1, respectively). Annual mean of Secchi depth
was 261 cm (n=30). A total 45 species of zooplankton were identified (28 rotifers, 12 cladocerans
and 5 copepods) during the study. The mean abundance of rotifers was highest (124±232 ind. L-1,
n=90) and that of cladocerans and copepods were relatively low (22±56 ind. L-1 and 13 ±30 ind.
L-1) in the whole layer. Total zooplankton abundance increased from late spring to summer, and
then declined and remained low throughout the winter. The annual mean of total zooplankton
filtration rate for phytoplankton at the lower layer was much higher than that of both layers
(upper layer: 44.4±107.8, middle layer: 95.1±436.4 and lower layer: 158.2±436.4 mL L-1 day-1).
Among the major zooplankton community, relative community filtration rate (RCFR, %) of copepods
for phytoplankton (50.2~54.8%) was much higher than that of cladocerans (27.7~36.3%)
and rotifers (8~17.6%). The seasonal variation of RCFRs of major zooplankton community was
observed. The RCFRs of rotifers were high in winter (44.6%, n=9), while the RCFRs of cladocerans
were high in summer (58.0%, n=7). In spring and fall, the RCFRs of copepods were high in
the whole layer (spring: 67.4%, n=9; fall: 74.4%, n=5).
The vertical changes (upper layer: 0~0.5 m, middle layer: 4~5 m and lower layer:
8~10 m) of the limnological variables, zooplankton dynamics and community filtration rate on
the phytoplankton were evaluated monthly intervals from November 2004 to June 2007 at the artificial
lake (Okjeong Lake). During the study, the annual mean of water temperatures were 15.2±
7.8�C (upper layer), 14.5±7.4�C (middle layer) and 13.0±6.2�C (lower layer), respectively (n=
30). The vertical variations of most limnological parameters (DO, pH, conductivity and turbidity)
were fairly similar, except for chl.-a concentration. Annual mean of chl.-a concentration was
highest at the upper layer (21.4 μg L-1), while annual means of concentrations were low at the
middle layer and lower layer (4.3 μgL-1 and 3.5 μgL-1, respectively). Annual mean of Secchi depth
was 261 cm (n=30). A total 45 species of zooplankton were identified (28 rotifers, 12 cladocerans
and 5 copepods) during the study. The mean abundance of rotifers was highest (124±232 ind. L-1,
n=90) and that of cladocerans and copepods were relatively low (22±56 ind. L-1 and 13 ±30 ind.
L-1) in the whole layer. Total zooplankton abundance increased from late spring to summer, and
then declined and remained low throughout the winter. The annual mean of total zooplankton
filtration rate for phytoplankton at the lower layer was much higher than that of both layers
(upper layer: 44.4±107.8, middle layer: 95.1±436.4 and lower layer: 158.2±436.4 mL L-1 day-1).
Among the major zooplankton community, relative community filtration rate (RCFR, %) of copepods
for phytoplankton (50.2~54.8%) was much higher than that of cladocerans (27.7~36.3%)
and rotifers (8~17.6%). The seasonal variation of RCFRs of major zooplankton community was
observed. The RCFRs of rotifers were high in winter (44.6%, n=9), while the RCFRs of cladocerans
were high in summer (58.0%, n=7). In spring and fall, the RCFRs of copepods were high in
the whole layer (spring: 67.4%, n=9; fall: 74.4%, n=5).