2
1.4
Defi nitions of Limnology
‘Limnology’ has been defi ned by various authors
in different ways, although the term ‘limnology’
was used historically as that branch of science
which deals exclusively with ‘lakes’. However,
since the days of Forel, there have grown two
different usages, both of which are extant today,
namely,
1.4.1 Restricted Usage
Here, limnology refers to the study of various
units of lentic or standing water series, i.e. lake/
wetland → pond → swamp.
1.4.2 Extended Usage
In this context, limnology is sometimes used to
include all forms of inland waters, namely, lentic
and lotic (running water series).
In other words, limnology attempts to embody
the study of all phenomena in freshwater.
Nevertheless, it would seem better to permit limnology to cover all forms of inland waters,
thereby including the inland salt waters as well
and any other inland water whose chemical content might seem to exclude them from the usual
concept of freshwater.
Welch ( 1935 ) conceived the problem of ‘biological productivity’ as the central theme of limnology. He had defi ned limnology as that branch
of science which deals with all causal infl uences
which determine it. This defi nition, it may be
noted here that, does not preclude any of the necessary stress on the different animal and plant
communities because they are the direct results
of the ‘biological productivity’ of waters which
they occupy.
According to Schwoerbel ( 1987 ), limnology
is the science of inland waters viewed as ecosystems together with their structure, materials and
energy balances. Kiihnelt considered limnology
as a subset of ecology along with ‘oceanography’ (which is concerned with marine ecosystem)
and ‘ Epheirology’ (which deals with terrestrial
habitats).
In short, limnology is the study of all aquatic
systems, both fresh and saline (including lakes,
wetlands, marshes, bogs, ponds, reservoirs,
streams, rivers, oceans) with regard to their physical, chemical and biological characteristics.
1.5
Other Terminologies
In addition to the above, certain other terms, like
hydrobiology, freshwater biology, aquatic biology and aquatic ecology, are sometimes used as
synonymous to the word ‘limnology’. But most
of these terms are names under which a diverse
variety of subject matter is included; and only a
part of it is strictly limnological in nature. Hence,
such terms, if they are to be used at all, be used
exclusively in connection with faunistic/fl oristic
studies. Further, the term ‘rheology’ is sometimes used to denote the running waters.
Wetlands are regarded as direct or indirect
life-supporting systems of the living world
including millions of human beings. It is known
that ancient civilisations had their origin and
growth on the banks of major rivers. Even today,
people use wetland soil for agriculture, catch fi sh
in the wetland for food, cut wetland trees for timber and fuelwood and wetland reeds to make
mats and thatched roofs. Other uses of wetland
include recreation, such as bird watching or sailing, or scientifi c study, fl ood control and nutrient
recycling ( Barbier et al. 1997 ). Extinction of
these wetlands is a growing concern all over the
world. The human-induced threats and improper
management systems are reducing the number of
these wetlands. In Karnataka, about 35 % wetlands are threatened due to sedimentation, 43 %
are subjected to encroachment, and 22 % have
rampant growth of exotic weeds. The catchment
area of Sharavathi river basin has treasured a
good number of small wetlands (swamps, tanks/
ponds, etc.). The downstream areas of these wetlands are highly valuable due to continuous water
availability and suitability of land for areca cultivation. The villagers in the surrounding area are
dependent on these tanks for domestic needs.
1 Introduction
1.4
Defi nitions of Limnology
‘Limnology’ has been defi ned by various authors
in different ways, although the term ‘limnology’
was used historically as that branch of science
which deals exclusively with ‘lakes’. However,
since the days of Forel, there have grown two
different usages, both of which are extant today,
namely,
1.4.1 Restricted Usage
Here, limnology refers to the study of various
units of lentic or standing water series, i.e. lake/
wetland → pond → swamp.
1.4.2 Extended Usage
In this context, limnology is sometimes used to
include all forms of inland waters, namely, lentic
and lotic (running water series).
In other words, limnology attempts to embody
the study of all phenomena in freshwater.
Nevertheless, it would seem better to permit limnology to cover all forms of inland waters,
thereby including the inland salt waters as well
and any other inland water whose chemical content might seem to exclude them from the usual
concept of freshwater.
Welch ( 1935 ) conceived the problem of ‘biological productivity’ as the central theme of limnology. He had defi ned limnology as that branch
of science which deals with all causal infl uences
which determine it. This defi nition, it may be
noted here that, does not preclude any of the necessary stress on the different animal and plant
communities because they are the direct results
of the ‘biological productivity’ of waters which
they occupy.
According to Schwoerbel ( 1987 ), limnology
is the science of inland waters viewed as ecosystems together with their structure, materials and
energy balances. Kiihnelt considered limnology
as a subset of ecology along with ‘oceanography’ (which is concerned with marine ecosystem)
and ‘ Epheirology’ (which deals with terrestrial
habitats).
In short, limnology is the study of all aquatic
systems, both fresh and saline (including lakes,
wetlands, marshes, bogs, ponds, reservoirs,
streams, rivers, oceans) with regard to their physical, chemical and biological characteristics.
1.5
Other Terminologies
In addition to the above, certain other terms, like
hydrobiology, freshwater biology, aquatic biology and aquatic ecology, are sometimes used as
synonymous to the word ‘limnology’. But most
of these terms are names under which a diverse
variety of subject matter is included; and only a
part of it is strictly limnological in nature. Hence,
such terms, if they are to be used at all, be used
exclusively in connection with faunistic/fl oristic
studies. Further, the term ‘rheology’ is sometimes used to denote the running waters.
Wetlands are regarded as direct or indirect
life-supporting systems of the living world
including millions of human beings. It is known
that ancient civilisations had their origin and
growth on the banks of major rivers. Even today,
people use wetland soil for agriculture, catch fi sh
in the wetland for food, cut wetland trees for timber and fuelwood and wetland reeds to make
mats and thatched roofs. Other uses of wetland
include recreation, such as bird watching or sailing, or scientifi c study, fl ood control and nutrient
recycling ( Barbier et al. 1997 ). Extinction of
these wetlands is a growing concern all over the
world. The human-induced threats and improper
management systems are reducing the number of
these wetlands. In Karnataka, about 35 % wetlands are threatened due to sedimentation, 43 %
are subjected to encroachment, and 22 % have
rampant growth of exotic weeds. The catchment
area of Sharavathi river basin has treasured a
good number of small wetlands (swamps, tanks/
ponds, etc.). The downstream areas of these wetlands are highly valuable due to continuous water
availability and suitability of land for areca cultivation. The villagers in the surrounding area are
dependent on these tanks for domestic needs.
1 Introduction