28
interaction with complex physical and chemical
systems. The continuing and exciting explorations of the other planets of the solar system,
including the moons of Jupiter, show that the
earth is unique. There is no other planet with a
biosphere in our solar system, no other planet
with lakes, rivers and oceans and no other planet
that could support life. There is an intricate
series of interactions between aquatic and terrestrial systems at the level of the biosphere. We
must consider both if we are to gain insights
into either. Numerous factors are involved in
maintaining the biosphere as a place suitable for
life, especially for man. It is not very diffi cult to
show that if anyone of them is modifi ed, the biosphere will be grossly different. These factors
extend from ‘life’ to infl ux of solar energy as
light and heat. They include the refl ectivity of
the earth. It is known that about two-thirds of
the surface of the earth is water. The continents
occupy certain positions relative to the axis of
rotation and the equator. All these factors affect
the climate worldwide. They, thus, bear directly
on the capacity of the earth for sustaining human
and other living populations.
Notwithstanding the above, the details about
the evolution of the biosphere remain obscure.
However, there are overwhelming evidences to
show that the relationships between the evolution
of life and the environment are reciprocal. It is
believed that the general conditions of life had
been remaining the same, perhaps, since a billion
of years. Biosphere is regarded not only the place
in which life exists, rather it is maintained by life
itself. The processes are complex. But, since
early in the history of the earth, the key process
had been the capacity for fi xing soil energy and
building carbon compounds.
2.3
Unity and Diversity of
Aquatic Systems
Nature does not bestow the ecologist or anyone
else with discrete and labelled entities or patches.
The natural world is a continuum. It is, perhaps,
‘man’ who has designed and imposed artifi cial
categories on nature, recognising such things as
species, ecosystems, populations, parasites, to
name but a few. Indeed, were he not to do so, all
sorts of enquiries and even communications
might have ceased. Yet, these abstractions may
not have any objective existence and they are,
perhaps, inherently undefi nable. The classifi cation of ‘habitat’ into ‘terrestrial’ and ‘aquatic’ is
one such characterisation, which, on analysis,
may not hold water. Over and above, in practice,
man carries the subdivision of the environment
much farther than that stated above. A peruse in
the subject could reveal that the aquatic habitat is
generally apportioned between fresh, marine,
brackish and inland salt (athalassic saline)
waters. Further, the freshwaters (FW) have been
subdivided into running water (lotic) and standing water (lentic) systems. Notwithstanding their
apparent differences, the various types of aquatic
systems, which have been recognised, all do
exhibit a fundamental unity.
There had been quite a large number of works
done on the basic nature of aquatic systems, notably, Hutchinson ( 1975 ), Hynes ( 1970 ), Wetzel
( 1983 ), Whitton ( 1975 ), Cushing and Walsh
( 1976 ), Barnes ( 1980 ), etc.
2.3.1 The Unity of Aquatic Systems
The aquatic systems undoubtedly comprise a
diverse assemblage of habitats, ranging from reedy
lakes to the open ocean and from mountain streams
to coral reefs. The magnifi cent habitat diversity is
refl ected in the bewildering diversity of their fl ora
and fauna. However, some habitats could be cited
without a single species of even a taxonomic order
or class in common.
Characteristically, any aquatic system could
be divided into three spatial compartments
regardless of precise habitat type. These are:
(a) The pelagic community of the water mass
(b) The benthic community living in and on the
underlying sediments or rock
(c) The fringing communities dominated by
emergent or submerged aquatic plants (generally in the shallow regions)
The different processes are located within
these compartments.
2 The Limnology of Lentic System
interaction with complex physical and chemical
systems. The continuing and exciting explorations of the other planets of the solar system,
including the moons of Jupiter, show that the
earth is unique. There is no other planet with a
biosphere in our solar system, no other planet
with lakes, rivers and oceans and no other planet
that could support life. There is an intricate
series of interactions between aquatic and terrestrial systems at the level of the biosphere. We
must consider both if we are to gain insights
into either. Numerous factors are involved in
maintaining the biosphere as a place suitable for
life, especially for man. It is not very diffi cult to
show that if anyone of them is modifi ed, the biosphere will be grossly different. These factors
extend from ‘life’ to infl ux of solar energy as
light and heat. They include the refl ectivity of
the earth. It is known that about two-thirds of
the surface of the earth is water. The continents
occupy certain positions relative to the axis of
rotation and the equator. All these factors affect
the climate worldwide. They, thus, bear directly
on the capacity of the earth for sustaining human
and other living populations.
Notwithstanding the above, the details about
the evolution of the biosphere remain obscure.
However, there are overwhelming evidences to
show that the relationships between the evolution
of life and the environment are reciprocal. It is
believed that the general conditions of life had
been remaining the same, perhaps, since a billion
of years. Biosphere is regarded not only the place
in which life exists, rather it is maintained by life
itself. The processes are complex. But, since
early in the history of the earth, the key process
had been the capacity for fi xing soil energy and
building carbon compounds.
2.3
Unity and Diversity of
Aquatic Systems
Nature does not bestow the ecologist or anyone
else with discrete and labelled entities or patches.
The natural world is a continuum. It is, perhaps,
‘man’ who has designed and imposed artifi cial
categories on nature, recognising such things as
species, ecosystems, populations, parasites, to
name but a few. Indeed, were he not to do so, all
sorts of enquiries and even communications
might have ceased. Yet, these abstractions may
not have any objective existence and they are,
perhaps, inherently undefi nable. The classifi cation of ‘habitat’ into ‘terrestrial’ and ‘aquatic’ is
one such characterisation, which, on analysis,
may not hold water. Over and above, in practice,
man carries the subdivision of the environment
much farther than that stated above. A peruse in
the subject could reveal that the aquatic habitat is
generally apportioned between fresh, marine,
brackish and inland salt (athalassic saline)
waters. Further, the freshwaters (FW) have been
subdivided into running water (lotic) and standing water (lentic) systems. Notwithstanding their
apparent differences, the various types of aquatic
systems, which have been recognised, all do
exhibit a fundamental unity.
There had been quite a large number of works
done on the basic nature of aquatic systems, notably, Hutchinson ( 1975 ), Hynes ( 1970 ), Wetzel
( 1983 ), Whitton ( 1975 ), Cushing and Walsh
( 1976 ), Barnes ( 1980 ), etc.
2.3.1 The Unity of Aquatic Systems
The aquatic systems undoubtedly comprise a
diverse assemblage of habitats, ranging from reedy
lakes to the open ocean and from mountain streams
to coral reefs. The magnifi cent habitat diversity is
refl ected in the bewildering diversity of their fl ora
and fauna. However, some habitats could be cited
without a single species of even a taxonomic order
or class in common.
Characteristically, any aquatic system could
be divided into three spatial compartments
regardless of precise habitat type. These are:
(a) The pelagic community of the water mass
(b) The benthic community living in and on the
underlying sediments or rock
(c) The fringing communities dominated by
emergent or submerged aquatic plants (generally in the shallow regions)
The different processes are located within
these compartments.
2 The Limnology of Lentic System