170
A. Sukenik et al.
heterogeneity over the western, central, and eastern parts of the lake. The lateral
difference, of course, was much smaller than that in summer. The slightly cooler
western parts of the lake are probably explained by the effect of cold Jordan River
water dispersing mainly along the western side of the lake, which could also be
identified by slightly lower specific conductivity (data not shown). The lateral
heterogeneity of water temperature, when the lake was vertically well mixed,
indicated that various parts of the lake could be somewhat isolated from each
other. This finding can be extremely important to understand spatial variations of
biochemical and biological processes.
During the summer, as Lake Kinneret is thermally stratified, higher turbidity
was measured in near-shore areas whereas the center of the lake was characterized
by notably lower turbidity (Fig. 3b). The high turbidity in the shallow zone is
probably due to resuspension of sediments by surface waves. In a previous study
Ostrovsky et al. (1996) suggested that elevated levels of algal biomass and
enhanced primary productivity in near-shore areas was due to an upward flux of
nutrient-rich hypolimnetic water. The higher turbidity detected at 20 m depth next
to the western coast and in 15-17 m depth next to the eastern coast were associated
with the metalimnetic layer, which tilted respectively (Fig. 3b and 3a). The
transportation of suspended solids from sites of resuspension, i.e., shallow littoral
zones, toward the center of the lake by metalimnetic jets was suggested by
Imberger (1998) and further demonstrated by Ostrovsky and Yacobi (1999). In the
winter, as the lake destratified, relatively narrow patches of high turbidity were
vertically and horizontally chaotically distributed over the entire monitored water
volume (Fig. 3d). This pattern presumably reflects the physical forces responsible
for water mixing in the winter and suggests the possible involvement of processes
that lead to local agglomeration or concentration of particles (planktonic or
inorganic substances).
Data from several transects were combined to produce a three-dimensional
array where each data point had its geographical position (longitude and latitude)
and depth. Data points of a studied parameter were then extracted from the entire
investigated water space to give the data within a given water depth layer, and an
interpolation procedure was used to calculate the pattern of areal distribution of
the relevant parameter. Analysis of Lake Kinneret during the summer time when
the lake was well stratified (Fig. 3a) revealed transparent water in the central area
of the lake whereas high turbidity areas were confined in the northeastern and
western parts (Fig. 4a). Later surveys operated in the winter, as the lake
destratified (Fig. 3c), revealed a less organized pattern of turbidity distribution.
Patches of low turbidity were identified in the north whereas higher turbidity was
measured along the eastern zone of the lake (Fig. 4b). This pattern was typical for
the unstable conditions of the winter characterized by low air temperatures, strong
winter storms with high wind velocity, rains, and river floods. A few weeks later,
as the lake restratified and a stable thermocline was established at ca. 12 m, the
turbidity distribution was arranged in a close to concentric pattern (Fig. 4c),
similar to the arrangement observed in the summer (Fig. 4a). While in the early
survey, done on June 2000 (Fig. 4), the east to west transects were 1.5 km apart, in
later surveys (Figure 4b, c) transects were separated from each other by 3 km.
A. Sukenik et al.
heterogeneity over the western, central, and eastern parts of the lake. The lateral
difference, of course, was much smaller than that in summer. The slightly cooler
western parts of the lake are probably explained by the effect of cold Jordan River
water dispersing mainly along the western side of the lake, which could also be
identified by slightly lower specific conductivity (data not shown). The lateral
heterogeneity of water temperature, when the lake was vertically well mixed,
indicated that various parts of the lake could be somewhat isolated from each
other. This finding can be extremely important to understand spatial variations of
biochemical and biological processes.
During the summer, as Lake Kinneret is thermally stratified, higher turbidity
was measured in near-shore areas whereas the center of the lake was characterized
by notably lower turbidity (Fig. 3b). The high turbidity in the shallow zone is
probably due to resuspension of sediments by surface waves. In a previous study
Ostrovsky et al. (1996) suggested that elevated levels of algal biomass and
enhanced primary productivity in near-shore areas was due to an upward flux of
nutrient-rich hypolimnetic water. The higher turbidity detected at 20 m depth next
to the western coast and in 15-17 m depth next to the eastern coast were associated
with the metalimnetic layer, which tilted respectively (Fig. 3b and 3a). The
transportation of suspended solids from sites of resuspension, i.e., shallow littoral
zones, toward the center of the lake by metalimnetic jets was suggested by
Imberger (1998) and further demonstrated by Ostrovsky and Yacobi (1999). In the
winter, as the lake destratified, relatively narrow patches of high turbidity were
vertically and horizontally chaotically distributed over the entire monitored water
volume (Fig. 3d). This pattern presumably reflects the physical forces responsible
for water mixing in the winter and suggests the possible involvement of processes
that lead to local agglomeration or concentration of particles (planktonic or
inorganic substances).
Data from several transects were combined to produce a three-dimensional
array where each data point had its geographical position (longitude and latitude)
and depth. Data points of a studied parameter were then extracted from the entire
investigated water space to give the data within a given water depth layer, and an
interpolation procedure was used to calculate the pattern of areal distribution of
the relevant parameter. Analysis of Lake Kinneret during the summer time when
the lake was well stratified (Fig. 3a) revealed transparent water in the central area
of the lake whereas high turbidity areas were confined in the northeastern and
western parts (Fig. 4a). Later surveys operated in the winter, as the lake
destratified (Fig. 3c), revealed a less organized pattern of turbidity distribution.
Patches of low turbidity were identified in the north whereas higher turbidity was
measured along the eastern zone of the lake (Fig. 4b). This pattern was typical for
the unstable conditions of the winter characterized by low air temperatures, strong
winter storms with high wind velocity, rains, and river floods. A few weeks later,
as the lake restratified and a stable thermocline was established at ca. 12 m, the
turbidity distribution was arranged in a close to concentric pattern (Fig. 4c),
similar to the arrangement observed in the summer (Fig. 4a). While in the early
survey, done on June 2000 (Fig. 4), the east to west transects were 1.5 km apart, in
later surveys (Figure 4b, c) transects were separated from each other by 3 km.