177
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_9, © Springer India 2013
9.1
Plankton
Hensen’s ( 1887 ) original defi nition of plankton
included all particulate organogenic material,
living or dead, passively drifting in the water.
Later workers had refi ned this concept and had
inevitably added to the terms used in describing
such as assemblage of particulate matter. For
both technical and theoretical reasons, it is often
desirable to consider together all the particulate
material present in the free water. This collectively is termed ‘seston’ (Kolkwitz 1912 ). The
seston consists of ‘bioseston’ (‘plankton’ and
‘nekton’, the latter being ordinarily quantitatively negligible) and ‘abioseston’ (‘tripton’)
(Wilhelmi 1917 ).
The term ‘nannoplankton’ was originally
coined to include everything not retained by a
tow net and is usually so used. Most authors
regard the total seston or plankton as consisting
roughly of net plankton (‘macro-, meso- and
some microplankton’) and nannoplankton (some
micro-, nanno- and ultra-plankton).
Among the other terms that had been employed,
‘euplankton’, implying a permanent planktonic
community; ‘meroplankton’, implying organisms
with temporary planktonic phases or stages; and
‘pseudoplankton’, for accidental plankters are
often useful. The distinction between the ‘limnoplankton’ of large lakes and the ‘helioplankton ’ of
ponds is useful, and the term ‘potamoplankton’
for the plankton of rivers is not infrequently
employed. For other terms, the philological reader
may consult Wilhelmi ( 1917 ) and Naumann
( 1931 ). Multiple prefi xes, as in ‘eulimnoplankton’, are occasionally useful but should be
employed very discretely.
In brief, the organisms of a lake are conveniently grouped ecologically into those associated with the free water, those associated with the
solid–water interface and those at the surface
fi lm.
The free water contains plankton (which are
not very effi cient in moving against turbulence)
and nekton (which, in a lake, can undertake
swimming movements in any direction in spite of
turbulence). Most animal plankters are actually
nektoplanktonic. The entire mass of suspended
matter in a volume of free water is called seston .
The non-living part is called tripton . All these
terms may be qualifi ed by prefi xes denoting size
classes. The euplankton constitutes the permanently planktonic species. The meroplankton is
planktonic only at certain times in their life
histories.
9.2
Seston
Sometimes, all the particulate materials in water
are considered as a whole. This is collectively
called seston . Seston consists of bioseston (which
includes plankton and nekton) and abioseston
(tripton).
9
Other Organisms in the Lakes
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_9, © Springer India 2013
9.1
Plankton
Hensen’s ( 1887 ) original defi nition of plankton
included all particulate organogenic material,
living or dead, passively drifting in the water.
Later workers had refi ned this concept and had
inevitably added to the terms used in describing
such as assemblage of particulate matter. For
both technical and theoretical reasons, it is often
desirable to consider together all the particulate
material present in the free water. This collectively is termed ‘seston’ (Kolkwitz 1912 ). The
seston consists of ‘bioseston’ (‘plankton’ and
‘nekton’, the latter being ordinarily quantitatively negligible) and ‘abioseston’ (‘tripton’)
(Wilhelmi 1917 ).
The term ‘nannoplankton’ was originally
coined to include everything not retained by a
tow net and is usually so used. Most authors
regard the total seston or plankton as consisting
roughly of net plankton (‘macro-, meso- and
some microplankton’) and nannoplankton (some
micro-, nanno- and ultra-plankton).
Among the other terms that had been employed,
‘euplankton’, implying a permanent planktonic
community; ‘meroplankton’, implying organisms
with temporary planktonic phases or stages; and
‘pseudoplankton’, for accidental plankters are
often useful. The distinction between the ‘limnoplankton’ of large lakes and the ‘helioplankton ’ of
ponds is useful, and the term ‘potamoplankton’
for the plankton of rivers is not infrequently
employed. For other terms, the philological reader
may consult Wilhelmi ( 1917 ) and Naumann
( 1931 ). Multiple prefi xes, as in ‘eulimnoplankton’, are occasionally useful but should be
employed very discretely.
In brief, the organisms of a lake are conveniently grouped ecologically into those associated with the free water, those associated with the
solid–water interface and those at the surface
fi lm.
The free water contains plankton (which are
not very effi cient in moving against turbulence)
and nekton (which, in a lake, can undertake
swimming movements in any direction in spite of
turbulence). Most animal plankters are actually
nektoplanktonic. The entire mass of suspended
matter in a volume of free water is called seston .
The non-living part is called tripton . All these
terms may be qualifi ed by prefi xes denoting size
classes. The euplankton constitutes the permanently planktonic species. The meroplankton is
planktonic only at certain times in their life
histories.
9.2
Seston
Sometimes, all the particulate materials in water
are considered as a whole. This is collectively
called seston . Seston consists of bioseston (which
includes plankton and nekton) and abioseston
(tripton).
9
Other Organisms in the Lakes