62
climatic and edaphic zones. The hypolimnial
oxygen supply in a deep oligotrophic lake during
summer, in contrast to shallow eutrophic lake, is
always richer to support a diversity of benthic
organisms. To the contrary, only a few species
could be found in the hypolimnion of shallow
eutrophic lakes. Rodhe ( 1969 ) suggested different rates of inorganic carbon fi xation by photosynthesis in these kinds of lakes.
5.4.3 Mesotrophic Lakes
Lakes in which the nutrient status is neither too
rich nor too poor are designated as mesotrophic
lakes. Mesotrophy lies somewhere in the range of
annual primary production of 25–75 g carbon
fi xation.
5.4.4 Dystrophic Lakes
These are said to be special kinds of lakes which
generally have high concentration of humic acid in
the water. Bog lakes, which are dystrophic in
nature, have low pH and gradually develop into
peat bogs which culminate into marshy wetlands.
5.5
Lake Evolution
Lakes are transient features of the landscape on
geological time scale. It is because, theoretically,
even the deepest lakes are gradually being fi lled
in by the accumulation of sediment. In the fi nal
stages, the lake turns to swamp and then to dry
land. This process is known as lake succession .
The question, thus, arises: How lakes are
formed?
Lakes are formed as a result of a number of
different processes which could be either natural
or artifi cial. These have been detailed above.
Places where lakes dominate the wetlands.
The greatest areas of freshwater in the world
are found in North America and East Africa.
The basins of the Great Lakes of North America
were formed by glacial action. They are so
enormous and form part of fi ngerlike and
U-shaped valleys. Conversely, in East Arica,
the lakes were formed tectonically. Also, one of
the largest lakes, the Lake Victoria, was, perhaps, formed by different associated tectonic
movements.
Summary
1. The lakes are of diverse type in the globe.
2. They are distributed from top of high mountains to plains, from tropics to the pole, from
northern hemisphere to southern hemisphere.
3. Lakes are classifi ed on the basis of different
aspects in order to bring systematicity in the
study.
4. Lakes are classifi ed on the basis of origin,
evolution, circulation and mixing, their position in the globe, nutrition, and so on.
5. Lakes are transient features of the landscape
on geological timescale. It is because, theoretically, even the deepest lakes are gradually
fi lled in by the accumulation of sediment.
Suggested Readings
Forel FA (1901) Handbuch der Seenkunde. Allgemeine.
Limnologie, Stuttgart, p 249
Hutchinson GE (1957) A Treatise on Limnology, vol I,
Geography, physics and chemistry. Wiley, New York,
pp ix + 1015
Rodhe W (1969) Sulla productione difi toplankton in laghi
transparents di alta montagna. Mem. 1
st
el Idrolbiol 15:
21–28
Thienemann A (1925) Die Binnergewä sser Mittelauropas
Die Binnengewä sser, 1, Verlag Schweizerbart,
Stutgart
Whipple GC (1927) The microscopy of drinking water,
4th edn., rev. by Fair and Whipple. Wiley, New York,
pp 586
5 Lakes in the Landscape, Their Classifi cation, Origin, Evolution
climatic and edaphic zones. The hypolimnial
oxygen supply in a deep oligotrophic lake during
summer, in contrast to shallow eutrophic lake, is
always richer to support a diversity of benthic
organisms. To the contrary, only a few species
could be found in the hypolimnion of shallow
eutrophic lakes. Rodhe ( 1969 ) suggested different rates of inorganic carbon fi xation by photosynthesis in these kinds of lakes.
5.4.3 Mesotrophic Lakes
Lakes in which the nutrient status is neither too
rich nor too poor are designated as mesotrophic
lakes. Mesotrophy lies somewhere in the range of
annual primary production of 25–75 g carbon
fi xation.
5.4.4 Dystrophic Lakes
These are said to be special kinds of lakes which
generally have high concentration of humic acid in
the water. Bog lakes, which are dystrophic in
nature, have low pH and gradually develop into
peat bogs which culminate into marshy wetlands.
5.5
Lake Evolution
Lakes are transient features of the landscape on
geological time scale. It is because, theoretically,
even the deepest lakes are gradually being fi lled
in by the accumulation of sediment. In the fi nal
stages, the lake turns to swamp and then to dry
land. This process is known as lake succession .
The question, thus, arises: How lakes are
formed?
Lakes are formed as a result of a number of
different processes which could be either natural
or artifi cial. These have been detailed above.
Places where lakes dominate the wetlands.
The greatest areas of freshwater in the world
are found in North America and East Africa.
The basins of the Great Lakes of North America
were formed by glacial action. They are so
enormous and form part of fi ngerlike and
U-shaped valleys. Conversely, in East Arica,
the lakes were formed tectonically. Also, one of
the largest lakes, the Lake Victoria, was, perhaps, formed by different associated tectonic
movements.
Summary
1. The lakes are of diverse type in the globe.
2. They are distributed from top of high mountains to plains, from tropics to the pole, from
northern hemisphere to southern hemisphere.
3. Lakes are classifi ed on the basis of different
aspects in order to bring systematicity in the
study.
4. Lakes are classifi ed on the basis of origin,
evolution, circulation and mixing, their position in the globe, nutrition, and so on.
5. Lakes are transient features of the landscape
on geological timescale. It is because, theoretically, even the deepest lakes are gradually
fi lled in by the accumulation of sediment.
Suggested Readings
Forel FA (1901) Handbuch der Seenkunde. Allgemeine.
Limnologie, Stuttgart, p 249
Hutchinson GE (1957) A Treatise on Limnology, vol I,
Geography, physics and chemistry. Wiley, New York,
pp ix + 1015
Rodhe W (1969) Sulla productione difi toplankton in laghi
transparents di alta montagna. Mem. 1
st
el Idrolbiol 15:
21–28
Thienemann A (1925) Die Binnergewä sser Mittelauropas
Die Binnengewä sser, 1, Verlag Schweizerbart,
Stutgart
Whipple GC (1927) The microscopy of drinking water,
4th edn., rev. by Fair and Whipple. Wiley, New York,
pp 586
5 Lakes in the Landscape, Their Classifi cation, Origin, Evolution