photosynthetic layer in the eastern area; however, the composition remained nearly
the same.
In the spring, the minimal concentrations of SOM components were recorded for
the surface water layer of the northern part of the central area, as was also observed
for the winter period (Figs. 10.3c,d and 10.4b). The average concentrations of C SOM
(14.5–15.3 μM) and N SOM (2.18–2.35 μM) increased by 2.0–2.4 times compared to
the winter period (Table 10.1). Meanwhile, the average C Chl concentration
decreased in the central area half as much and by 1.2 times in the eastern area,
varying 0.49–0.57 mg/m
3 . The ratios of C/Chl (400–600) and C/N (7.0–7.6) in both
areas may testify to low productivity in these regions during the spring period.
The weighted averages of C SOM and N SOM in the photosynthetic water layer
increased by 1.8 and 2.2 times in the central area, and by 1.1 and 1.5 times in the
eastern area, respectively, compared to those observed during the winter period.
However, they were less than 1.2–1.3 times compared to those observed in the
surface water layer. The C Ch l concentration in both areas remained the same
compared to the winter period. The average C/Chl values decreased down to
274–302 in both areas, and the C/N ratio also decreased down to 6.1–6.9. We
argue the increasing rate of phytoplankton in SOM compared to the winter period
and the fact that SOM was represented mostly by phytoplankton and newly formed
detritus.
During the summer period, patches of low concentrations of SOM components
remained in the central area (Figs. 10.3e,f and 10.4c). The average C SOM concentration did dot change in the surface layer compared to the spring period. Meanwhile, the N SOM concentration in the northern area decreased by 1.7 times, but the
C Chl concentration increased by 1.6 times. In the eastern area, the concentrations of
C SOM and N SOM increased by 1.3 times, and the C Chl concentration, in 2.2 times,
exceeding the values recorded in the central area. The high C/Chl (800) and C/N
(8.9–10.2) ratios in both areas testified to prevailing well transformed detritus in the
SOM composition.
The weighted averages of C SOM and N SOM in the photosynthetic water layer in
both areas increased by 1.2–1.7 times compared to those observed during the spring
period. Meanwhile, the chlorophyll a concentration decreased insignificantly in the
central area and increased by 1.7 times in the eastern area. The concentrations of
C SOM and N SOM here increased by 1.1–1.4 times compared to the surface layer
(a decrease in these parameters was recorded in spring). In the eastern area, the
C SOM concentration decreased by 1.1 times, but the N SOM concentration increased
slightly. The average C/Chl ratio decreased slightly in the photosynthetic layer
compared to the surface layer, but still remained high (475–770). The average C/N
ratio in this layer also decreased slightly, constituting 8.2 in the central area and 6.7
in the eastern area. This may testify to an increase in the ratio of freshly formed
detritus in the SOM in the photosynthetic layer. We also assume that the biological
productivity of the central and eastern areas was lower in the summer period
compared to the springtime.
During the autumn period, the average concentrations of C SOM and N SOM in the
surface water layer decreased by 1.2–1.4 times compared to the summertime.
10 Seasonal Changes of Hydrobiological and Bio-Optical Parameters in the. . .
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the same.
In the spring, the minimal concentrations of SOM components were recorded for
the surface water layer of the northern part of the central area, as was also observed
for the winter period (Figs. 10.3c,d and 10.4b). The average concentrations of C SOM
(14.5–15.3 μM) and N SOM (2.18–2.35 μM) increased by 2.0–2.4 times compared to
the winter period (Table 10.1). Meanwhile, the average C Chl concentration
decreased in the central area half as much and by 1.2 times in the eastern area,
varying 0.49–0.57 mg/m
3 . The ratios of C/Chl (400–600) and C/N (7.0–7.6) in both
areas may testify to low productivity in these regions during the spring period.
The weighted averages of C SOM and N SOM in the photosynthetic water layer
increased by 1.8 and 2.2 times in the central area, and by 1.1 and 1.5 times in the
eastern area, respectively, compared to those observed during the winter period.
However, they were less than 1.2–1.3 times compared to those observed in the
surface water layer. The C Ch l concentration in both areas remained the same
compared to the winter period. The average C/Chl values decreased down to
274–302 in both areas, and the C/N ratio also decreased down to 6.1–6.9. We
argue the increasing rate of phytoplankton in SOM compared to the winter period
and the fact that SOM was represented mostly by phytoplankton and newly formed
detritus.
During the summer period, patches of low concentrations of SOM components
remained in the central area (Figs. 10.3e,f and 10.4c). The average C SOM concentration did dot change in the surface layer compared to the spring period. Meanwhile, the N SOM concentration in the northern area decreased by 1.7 times, but the
C Chl concentration increased by 1.6 times. In the eastern area, the concentrations of
C SOM and N SOM increased by 1.3 times, and the C Chl concentration, in 2.2 times,
exceeding the values recorded in the central area. The high C/Chl (800) and C/N
(8.9–10.2) ratios in both areas testified to prevailing well transformed detritus in the
SOM composition.
The weighted averages of C SOM and N SOM in the photosynthetic water layer in
both areas increased by 1.2–1.7 times compared to those observed during the spring
period. Meanwhile, the chlorophyll a concentration decreased insignificantly in the
central area and increased by 1.7 times in the eastern area. The concentrations of
C SOM and N SOM here increased by 1.1–1.4 times compared to the surface layer
(a decrease in these parameters was recorded in spring). In the eastern area, the
C SOM concentration decreased by 1.1 times, but the N SOM concentration increased
slightly. The average C/Chl ratio decreased slightly in the photosynthetic layer
compared to the surface layer, but still remained high (475–770). The average C/N
ratio in this layer also decreased slightly, constituting 8.2 in the central area and 6.7
in the eastern area. This may testify to an increase in the ratio of freshly formed
detritus in the SOM in the photosynthetic layer. We also assume that the biological
productivity of the central and eastern areas was lower in the summer period
compared to the springtime.
During the autumn period, the average concentrations of C SOM and N SOM in the
surface water layer decreased by 1.2–1.4 times compared to the summertime.
10 Seasonal Changes of Hydrobiological and Bio-Optical Parameters in the. . .
163