88
with the water supply and this is frequently very
variable from year to year.
6.6.1 The Great Salt Lake
The Great Salt Lake lies in Utah in the USA. It
provides an example of biological aspects of a
salt lake and also on the geographical and biological implications of fl uctuating water levels in
shallow closed lake basin. The present lake is the
remnant of Lake Bonneville which had an area of
>50,000 km
2 about 14,000–16,000 years ago. It
used to extend from Idaho in the north to eastern
Nevada in the west. The lake was >300 m deep. It
used to drain out from the north through the
Snake River. From the end of the last Ice Age, the
lake level gradually declined through a series of
fl uctuating stages.
There have been some major biological consequences of the dilution of the lake. The brine
shrimps ( Artemia ) are all but disappeared, not
because they cannot live in the less salty water
but because the dilution appears to have
allowed the development of huge populations
of predatory corixids. It may be noted here that
the waters of both the Great Salt Lakes and
Dead Sea contain some of the more specialised
biota. All living cells contain salts, similar to
those in seawater, dissolved in their watery
cytoplasm.
6.6.2 The Dead Sea
It is the most concentrated natural salt lake in the
world. It lies (31° 30′ N; 35° 30′ E; altitude
400 m below sea level; lake area 940 km
2 ; lake
volume 136 km
3 ; maximum depth 330 m) at the
lowest point on the earth’s land surface. The bottom
of the lake bed is 748 m below the sea level. It
lies in part of the Syrio-African Rift. It extends
for 6,500 km from Syria, through the Red Sea
and Africa as far south as Lake Malawi.
This area was connected to the Mediterranean
Sea during the Pliocene (5–2 million years ago).
The Dead Sea is now much reduced due to
upstream abstraction for irrigation. The salt also
increased the density of Dead Sea water. Hence,
sinking and diving are almost impossible in the
Dead Sea. The concentrations of salts in the Dead
Sea is about 350 g per lit. Hence, the water is
highly saturated with salt.
It is hardly surprising to note that nothing lives
in the Dead Sea water. The only exceptions are a
few extraordinary bacteria, namely, Halobacterium
halobium . In fact, these bacteria die, if water is
diluted.
Exploitation of mineral salts dissolved in the
Dead Sea has been going on since many years.
6.6.3 Soda Lakes of the African Rift
Valleys
Eastern Africa is one of the major lakeland areas
of the world. It contains many types of lakes.
They range from some of the largest and deepest
lakes of the earth to tiny lakes in volcanic craters,
from pure FW lake to concentrated soda lakes
and from ice-covered mountain lakes to hot
springs which are never cool. Most of the lakes in
Eastern Rift are very different from the large,
deep lakes of the Western Rift, and many of them
are highly saline. In most of the African saline
lakes, sodium carbonate instead of sodium chloride is the principal salt, unlike in the Great Salt
Lake. The former also contains great variety of
other salts.
There are two groups of large lakes on the
fl oor of the Rift Valley to the north, in Ethiopia.
(A) The fi rst group includes the following lakes
lying at altitudes ranging from 1,558 to
1,680 m MSL:
6.6.4 Lake Zwali
It is the shallowest (max. depth 8 m) but largest in
surface area (654 km
2 ) saline lake.
6.6.5 Lake Shala
It is the deepest (max. depth 266 m) and most
saline (20 000–30 000 μ S cm
−1 ).
6 Lakes of the World
with the water supply and this is frequently very
variable from year to year.
6.6.1 The Great Salt Lake
The Great Salt Lake lies in Utah in the USA. It
provides an example of biological aspects of a
salt lake and also on the geographical and biological implications of fl uctuating water levels in
shallow closed lake basin. The present lake is the
remnant of Lake Bonneville which had an area of
>50,000 km
2 about 14,000–16,000 years ago. It
used to extend from Idaho in the north to eastern
Nevada in the west. The lake was >300 m deep. It
used to drain out from the north through the
Snake River. From the end of the last Ice Age, the
lake level gradually declined through a series of
fl uctuating stages.
There have been some major biological consequences of the dilution of the lake. The brine
shrimps ( Artemia ) are all but disappeared, not
because they cannot live in the less salty water
but because the dilution appears to have
allowed the development of huge populations
of predatory corixids. It may be noted here that
the waters of both the Great Salt Lakes and
Dead Sea contain some of the more specialised
biota. All living cells contain salts, similar to
those in seawater, dissolved in their watery
cytoplasm.
6.6.2 The Dead Sea
It is the most concentrated natural salt lake in the
world. It lies (31° 30′ N; 35° 30′ E; altitude
400 m below sea level; lake area 940 km
2 ; lake
volume 136 km
3 ; maximum depth 330 m) at the
lowest point on the earth’s land surface. The bottom
of the lake bed is 748 m below the sea level. It
lies in part of the Syrio-African Rift. It extends
for 6,500 km from Syria, through the Red Sea
and Africa as far south as Lake Malawi.
This area was connected to the Mediterranean
Sea during the Pliocene (5–2 million years ago).
The Dead Sea is now much reduced due to
upstream abstraction for irrigation. The salt also
increased the density of Dead Sea water. Hence,
sinking and diving are almost impossible in the
Dead Sea. The concentrations of salts in the Dead
Sea is about 350 g per lit. Hence, the water is
highly saturated with salt.
It is hardly surprising to note that nothing lives
in the Dead Sea water. The only exceptions are a
few extraordinary bacteria, namely, Halobacterium
halobium . In fact, these bacteria die, if water is
diluted.
Exploitation of mineral salts dissolved in the
Dead Sea has been going on since many years.
6.6.3 Soda Lakes of the African Rift
Valleys
Eastern Africa is one of the major lakeland areas
of the world. It contains many types of lakes.
They range from some of the largest and deepest
lakes of the earth to tiny lakes in volcanic craters,
from pure FW lake to concentrated soda lakes
and from ice-covered mountain lakes to hot
springs which are never cool. Most of the lakes in
Eastern Rift are very different from the large,
deep lakes of the Western Rift, and many of them
are highly saline. In most of the African saline
lakes, sodium carbonate instead of sodium chloride is the principal salt, unlike in the Great Salt
Lake. The former also contains great variety of
other salts.
There are two groups of large lakes on the
fl oor of the Rift Valley to the north, in Ethiopia.
(A) The fi rst group includes the following lakes
lying at altitudes ranging from 1,558 to
1,680 m MSL:
6.6.4 Lake Zwali
It is the shallowest (max. depth 8 m) but largest in
surface area (654 km
2 ) saline lake.
6.6.5 Lake Shala
It is the deepest (max. depth 266 m) and most
saline (20 000–30 000 μ S cm
−1 ).
6 Lakes of the World